Help for package sentopics

Type:

Package

Title:

Tools for Joint Sentiment and Topic Analysis of Textual Data

Version:

0.7.4

Date:

2024-09-20

Maintainer:

Olivier Delmarcelle <delmarcelle.olivier@gmail.com>

Description:

A framework that joins topic modeling and sentiment analysis of textual data. The package implements a fast Gibbs sampling estimation of Latent Dirichlet Allocation (Griffiths and Steyvers (2004) <doi:10.1073/pnas.0307752101>) and Joint Sentiment/Topic Model (Lin, He, Everson and Ruger (2012) <doi:10.1109/TKDE.2011.48>). It offers a variety of helpers and visualizations to analyze the result of topic modeling. The framework also allows enriching topic models with dates and externally computed sentiment measures. A flexible aggregation scheme enables the creation of time series of sentiment or topical proportions from the enriched topic models. Moreover, a novel method jointly aggregates topic proportions and sentiment measures to derive time series of topical sentiment.

License:

GPL (≥ 3)

BugReports:

https://github.com/odelmarcelle/sentopics/issues

URL:

https://github.com/odelmarcelle/sentopics

Encoding:

UTF-8

Depends:

R (≥ 3.5.0)

Imports:

Rcpp (≥ 1.0.4.6), methods, generics, quanteda (≥ 3.2.0), data.table (≥ 1.13.6), RcppHungarian

Suggests:

ggplot2, ggridges, plotly, RColorBrewer, xts, zoo, future, future.apply, progressr, progress, testthat, covr, stm, lda, topicmodels, seededlda (≥ 1.4.0), keyATM, LDAvis, servr, textcat, stringr, sentometrics, spacyr, knitr, rmarkdown, webshot

LinkingTo:

Rcpp, RcppArmadillo, RcppProgress

RcppModules:

model_module

RoxygenNote:

7.3.1

LazyData:

true

VignetteBuilder:

knitr

NeedsCompilation:

yes

Packaged:

2024-09-20 11:49:28 UTC; odlmarce

Author:

Olivier Delmarcelle

[aut, cre], Samuel Borms

[ctb], Chengua Lin [cph] (Original JST implementation), Yulan He [cph] (Original JST implementation), Jose Bernardo [cph] (Original JST implementation), David Robinson [cph] (Implementation of reorder_within()), Julia Silge

[cph] (Implementation of reorder_within())

Repository:

CRAN

Date/Publication:

2024-09-20 12:20:02 UTC

Tools for joining sentiment and topic analysis (sentopics)

Description

sentopics provides function to easily estimate a range of topic models and process their output. Particularly, it facilitates the integration of topic analysis with a time dimension through time-series generating functions. In addition, sentopics interacts with sentiment analysis to compute the sentiment conveyed by topics. Finally, the package implements a number of visualization helping interpreting the results of topic models.

Usage

Please refer to the vignettes for a comprehensive introduction to the package functions.

Basic usage: Introduction to topic model estimation with sentopics
Topical time series: Integrate topic analysis with sentiment analysis along a time dimension

For further details, you may browse the package documentation.

Note

Please cite the package in publications. Use citation("sentopics").

Author(s)

Maintainer: Olivier Delmarcelle delmarcelle.olivier@gmail.com (ORCID)

Other contributors:

Samuel Borms samuel.borms@unine.ch (ORCID) [contributor]
Chengua Lin chenghua.lin@abdn.ac.uk (Original JST implementation) [copyright holder]
Yulan He yulan.he@warwick.ac.uk (Original JST implementation) [copyright holder]
Jose Bernardo (Original JST implementation) [copyright holder]
David Robinson admiral.david@gmail.com (Implementation of reorder_within()) [copyright holder]
Julia Silge julia.silge@gmail.com (ORCID) (Implementation of reorder_within()) [copyright holder]

Corpus of press conferences from the European Central Bank

Description

A corpus of 260 ECB press conference, split into 4224 paragraphs. The corpus contains a number of docvars indicating the date of the press conference and a measured sentiment based on the Loughran-McDonald lexicon.

Usage

ECB_press_conferences

Format

A quanteda::corpus object.

Source

https://www.ecb.europa.eu/press/key/date/html/index.en.html.

Examples

docvars(ECB_press_conferences)

Tokenized press conferences

Description

The pre-processed and tokenized version of the ECB_press_conferences corpus of press conferences. The processing involved the following steps:

Subset paragraphs shorter than 10 words
Removal of stop words
Part-of-speech tagging, following which only nouns, proper nouns and adjective were retained.
Detection and merging of frequent compound words
Frequency-based cleaning of rare and very common words

Usage

ECB_press_conferences_tokens

Format

A quanteda::tokens object.

Source

https://www.ecb.europa.eu/press/key/date/html/index.en.html.

Examples

LDA(ECB_press_conferences_tokens)

Create a Joint Sentiment/Topic model

Description

This function initialize a Joint Sentiment/Topic model.

Usage

JST(
  x,
  lexicon = NULL,
  S = 3,
  K = 5,
  gamma = 1,
  alpha = 5,
  beta = 0.01,
  gammaCycle = 0,
  alphaCycle = 0
)

Arguments

x

tokens object containing the texts. A coercion will be attempted if x is not a tokens.

lexicon

a quanteda dictionary with positive and negative categories

S

the number of sentiments

K

the number of topics

gamma

the hyperparameter of sentiment-document distribution

alpha

the hyperparameter of topic-document distribution

beta

the hyperparameter of vocabulary distribution

gammaCycle

integer specifying the cycle size between two updates of the hyperparameter alpha

alphaCycle

integer specifying the cycle size between two updates of the hyperparameter alpha

Details

The rJST.LDA methods enable the transition from a previously estimated LDA model to a sentiment-aware rJST model. The function retains the previously estimated topics and randomly assigns sentiment to every word of the corpus. The new model will retain the iteration count of the initial LDA model.

Value

An S3 list containing the model parameter and the estimated mixture. This object corresponds to a Gibbs sampler estimator with zero iterations. The MCMC can be iterated using the fit() function.

tokens is the tokens object used to create the model
vocabulary contains the set of words of the corpus
it tracks the number of Gibbs sampling iterations
za is the list of topic assignment, aligned to the tokens object with padding removed
logLikelihood returns the measured log-likelihood at each iteration, with a breakdown of the likelihood into hierarchical components as attribute

The topWords() function easily extract the most probables words of each topic/sentiment.

Author(s)

Olivier Delmarcelle

References

Lin, C. and He, Y. (2009). Joint sentiment/topic model for sentiment analysis. In Proceedings of the 18th ACM conference on Information and knowledge management, 375–384.

Lin, C., He, Y., Everson, R. and Ruger, S. (2012). Weakly Supervised Joint Sentiment-Topic Detection from Text. IEEE Transactions on Knowledge and Data Engineering, 24(6), 1134–-1145.

Examples

# creating a JST model
JST(ECB_press_conferences_tokens)

# estimating a JST model including a lexicon
jst <- JST(ECB_press_conferences_tokens, lexicon = LoughranMcDonald)
jst <- fit(jst, 100)

Create a Latent Dirichlet Allocation model

Description

This function initialize a Latent Dirichlet Allocation model.

Usage

LDA(x, K = 5, alpha = 1, beta = 0.01)

Arguments

x

tokens object containing the texts. A coercion will be attempted if x is not a tokens.

K

the number of topics

alpha

the hyperparameter of topic-document distribution

beta

the hyperparameter of vocabulary distribution

Details

Value

An S3 list containing the model parameter and the estimated mixture. This object corresponds to a Gibbs sampler estimator with zero iterations. The MCMC can be iterated using the fit() function.

tokens is the tokens object used to create the model
vocabulary contains the set of words of the corpus
it tracks the number of Gibbs sampling iterations
za is the list of topic assignment, aligned to the tokens object with padding removed
logLikelihood returns the measured log-likelihood at each iteration, with a breakdown of the likelihood into hierarchical components as attribute

The topWords() function easily extract the most probables words of each topic/sentiment.

Author(s)

Olivier Delmarcelle

References

Blei, D.M., Ng, A.Y. and Jordan, M.I. (2003). Latent Dirichlet Allocation. Journal of Machine Learning Research, 3, 993–1022.

Examples

# creating a model
LDA(ECB_press_conferences_tokens, K = 5, alpha = 0.1, beta = 0.01)

# estimating an LDA model
lda <- LDA(ECB_press_conferences_tokens)
lda <- fit(lda, 100)

Visualize a LDA model using LDAvis

Description

This function call LDAvis to create a dynamic visualization of an estimated topic model.

Usage

LDAvis(x, ...)

Arguments

x

an LDA model

...

further arguments passed on to LDAvis::createJSON() and LDAvis::serVis().

Details

The CRAN release of LDAvis does not support UTF-8 characters and automatically reorder topics. To solve these two issues, please install the development version of LDAvis from github (devtools::install_github("cpsievert/LDAvis")).

Value

Nothing, called for its side effects.

Examples

lda <- LDA(ECB_press_conferences_tokens)
lda <- fit(lda, 100)
LDAvis(lda)

Loughran-McDonald lexicon

Description

The Loughran-McDonald lexicon for financial texts adapted for usage in sentopics. The lexicon is enhanced with two list of valence-shifting words.

Usage

LoughranMcDonald

Format

A quanteda::dictionary containing two polarity categories (negative and positive) and two valence-shifting categories (negator and amplifier).

Source

https://sraf.nd.edu/loughranmcdonald-master-dictionary/ for the lexicon and lexicon::hash_valence_shifters for the valence shifters.

References

Loughran, T. & McDonald, B. (2011). When Is a Liability Not a Liability? Textual Analysis, Dictionaries, and 10-Ks. The Journal of Finance, 66(1), 35–65.doi:10.1111/j.1540-6261.2010.01625.x

Examples

JST(ECB_press_conferences_tokens, lexicon = LoughranMcDonald)

Picault-Renault lexicon

Description

The Picault-Renault lexicon, specialized in the analysis of central bank communication. The lexicon identifies a large number of n-grams and gives their probability to belong to six categories:

Monetary Policy - accommodative
Monetary Policy - neutral
Monetary Policy - restrictive
Economic Condition - negative
Economic Condition - neutral
Economic Condition - positive

Usage

PicaultRenault

Format

A data.table::data.table object.

Source

http://www.cbcomindex.com/lexicon.php

References

Picault, M. & Renault, T. (2017). Words are not all created equal: A new measure of ECB communication. Journal of International Money and Finance, 79, 136–156. doi:10.1016/j.jimonfin.2017.09.005

Examples

head(PicaultRenault)

Regression dataset based on Picault & Renault (2017)

Description

A regression dataset built to partially replicate the result of Picault & Renault. This dataset contains, for each press conference published after 2000:

The Main Refinancing Rate (MRR) of the ECB set following the press conference
The change in the MRR following the press conference
The change in the MRR observed at the previous press conference
The Bloomberg consensus on the announced MRR
The Surprise brought by the announcement, computed as the Bloomberg consensus minus the MRR following the conference
The EURO STOXX 50 return on the day of the press conference
The EURO STOXX 50 return on the day preceding the announcement

Usage

PicaultRenault_data

Format

An xts::xts object.

Source

The data was manually prepared by the author of this package.

References

Picault, M. & Renault, T. (2017). Words are not all created equal: A new measure of ECB communication. Journal of International Money and Finance, 79, 136–156. doi:10.1016/j.jimonfin.2017.09.005

Examples

head(PicaultRenault_data)

Conversions from other packages to LDA

Description

These functions converts estimated models from other topic modeling packages to the format used by sentopics.

Usage

as.LDA(x, ...)

## S3 method for class 'STM'
as.LDA(x, docs, ...)

## S3 method for class 'LDA_Gibbs'
as.LDA(x, docs, ...)

## S3 method for class 'LDA_VEM'
as.LDA(x, docs, ...)

## S3 method for class 'textmodel_lda'
as.LDA(x, ...)

as.LDA_lda(list, docs, alpha, eta)

## S3 method for class 'keyATM_output'
as.LDA(x, docs, ...)

Arguments

x

an estimated topic model from stm, topicmodels or seededlda.

...

arguments passed to other methods.

docs

for some objects, the documents used to initialize the model.

list

the list containing an estimated model from lda.

alpha

for lda models, the document-topic mixture hyperparameter. If missing, the hyperparameter will be set to 50/K.

eta

for lda models, the topic-word mixture hyperparameter. Other packages refer to this hyperparameter as beta. If missing, the hyperparameter will be set to 0.01.

Details

Some models do not store the topic assignment of each word (for example, estimated through variational inference). For these, the conversion is limited and some functionalities of sentopics will be disabled. The list of affected functions is subject to change and currently includes fit(), mergeTopics() and rJST.LDA().

Since models from the lda package are simply lists of outputs, the function as.LDA_lda() is not related to the other methods and should be applied directly on lists containing a model.

Value

A S3 list of class LDA, as if it was created and estimated using LDA() and fit().

Examples


## stm
library("stm")
stm <- stm(poliblog5k.docs, poliblog5k.voc, K=25,
           prevalence=~rating, data=poliblog5k.meta,
           max.em.its=2, init.type="Spectral")
as.LDA(stm, docs = poliblog5k.docs)

## lda
library("lda")
data("cora.documents")
data("cora.vocab")
lda <- lda.collapsed.gibbs.sampler(cora.documents,
                                   5, ## Num clusters
                                   cora.vocab,
                                   100, ## Num iterations
                                   0.1,
                                   0.1)
LDA <- as.LDA_lda(lda, docs = cora.documents, alpha = .1, eta = .1)

## topicmodels
data("AssociatedPress", package = "topicmodels")
lda <- topicmodels::LDA(AssociatedPress[1:20,],
                        control = list(alpha = 0.1), k = 2)
LDA <- as.LDA(lda, docs = AssociatedPress[1:20,])

## seededlda
library("seededlda")
lda <- textmodel_lda(dfm(ECB_press_conferences_tokens),
                     k = 6, max_iter = 100)
LDA <- as.LDA(lda)

## keyATM
library("keyATM")
data(keyATM_data_bills, package = "keyATM")
keyATM_docs <- keyATM_read(keyATM_data_bills$doc_dfm)
out <- keyATM(docs = keyATM_docs, model = "base",
              no_keyword_topics = 5,
              keywords = keyATM_data_bills$keywords)
LDA <- as.LDA(out, docs = keyATM_docs)

Convert back a dfm to a tokens object

Description

Convert back a dfm to a tokens object

Usage

## S3 method for class 'dfm'
as.tokens(
  x,
  concatenator = NULL,
  tokens = NULL,
  ignore_list = NULL,
  case_insensitive = FALSE,
  padding = TRUE,
  ...
)

Arguments

x

quanteda::dfm to be coerced

concatenator

only used for consistency with the generic

tokens

optionally, the tokens from which the dfm was created. Providing the initial tokens will ensure that the word order will be respected in the coerced object.

ignore_list

a character vector of words that should not be removed from the initial tokens object. Useful to avoid removing some lexicon word following the usage of quanteda::dfm_trim().

case_insensitive

only used when the tokens argument is provided. Default to FALSE. This function removes words in the initial tokens based on the remaining features in the quanteda::dfm object. This check is case-sensitive by default, and can be relaxed by setting this argument to TRUE.

padding

if TRUE, leaves an empty string where the removed tokens previously existed. The use of padding is encouraged to improve the behavior of the coherence metrics (see coherence()) that rely on word positions.

...

unused

Value

a quanteda quanteda::tokens object.

Examples

library("quanteda")
dfm <- dfm(ECB_press_conferences_tokens, tolower = FALSE)
dfm <- dfm_trim(dfm, min_termfreq = 200)
as.tokens(dfm)
as.tokens(dfm, tokens = ECB_press_conferences_tokens)
as.tokens(dfm, tokens = ECB_press_conferences_tokens, padding = FALSE)

Distances between topic models (chains)

Description

Computes the distance between different estimates of a topic model. Since the estimation of a topic model is random, the results may largely differ as the process is repeated. This function allows to compute the distance between distinct realizations of the estimation process. Estimates are referred to as chains.

Usage

chainsDistances(
  x,
  method = c("euclidean", "hellinger", "cosine", "minMax", "naiveEuclidean",
    "invariantEuclidean"),
  ...
)

Arguments

x

a valid multiChains object, obtained through the estimation of a topic model using fit() and the argument nChains greater than 1.

method

the method used to measure the distance between chains.

...

further arguments passed to internal distance functions.

Details

The method argument determines how are computed distance.

euclidean finds the pairs of topics that minimizes and returns the total Euclidean distance.
hellinger does the same but based on the Hellinger distance.
cosine does the same but based on the Cosine distance.
minMax computes the maximum distance among the best pairs of distances. Inspired by the minimum-matching distance from Tang et al. (2014).
naiveEuclidean computes the Euclidean distance without searching for the best pairs of topics.
invariantEuclidean computes the best pairs of topics for all allowed permutations of topic indices. For JST and reversed-JST models, the two- levels hierarchy of document-sentiment-topic leads some permutations of indices to represent a drastically different outcome. This setting restricts the set of permutations to the ones that do not change the interpretation of the model. Equivalent to euclidean for LDA models.

Value

A matrix of distance between the elements of x

Author(s)

Olivier Delmarcelle

References

Tang, J., Meng, Z., Nguyen, X., Mei, Q., and Zhang, M. (2014). Understanding the Limiting Factors of Topic Modeling via Posterior Contraction Analysis. In Proceedings of the 31st International Conference on Machine Learning, 32, 90–198.

Examples

model <- LDA(ECB_press_conferences_tokens)
model <- fit(model, 10, nChains = 5)
chainsDistances(model)

Compute scores of topic models (chains)

Description

Compute various scores (log likelihood, coherence) for a list of topic models.

Usage

chainsScores(x, window = 110, nWords = 10)

Arguments

x

a valid multiChains object, obtained through the estimation of a topic model using fit() and the argument nChains greater than 1.

window

optional. If NULL, use the default window for each coherence metric (10 for C_NPMI and 110 for C_V). It is possible to override these default windows by providing an integer or "boolean" to this argument, determining a new window size for all measures.

nWords

the number of words used to compute coherence. See coherence().

Value

A data.table with some statistics about each chain. For the coherence metrics, the value shown is the mean coherence across all topics of a chain

Parallelism

When nChains > 1, the function can take advantage of future.apply::future_lapply (if installed) to spread the computation over multiple processes. This requires the specification of a parallel strategy using future::plan(). See the examples below.

Examples

model <- LDA(ECB_press_conferences_tokens[1:10])
model <- fit(model, 10, nChains = 5)
chainsScores(model, window = 5)
chainsScores(model, window = "boolean")

# -- Parallel computation --
require(future.apply)
future::plan("multisession", workers = 2) # Set up 2 workers
chainsScores(model, window = "boolean")

future::plan("sequential") # Shut down workers

Coherence of estimated topics

Description

Computes various coherence based metrics for topic models. It assesses the quality of estimated topics based on co-occurrences of words. For best results, consider cleaning the initial tokens object with padding = TRUE.

Usage

coherence(
  x,
  nWords = 10,
  method = c("C_NPMI", "C_V"),
  window = NULL,
  NPMIs = NULL
)

Arguments

x

a model created from the LDA(), JST() or rJST() function and estimated with fit()

nWords

the number of words in each topic used for evaluation.

method

the coherence method used.

window

NPMIs

optional NPMI matrix. If provided, skip the computation of NPMI between words, substantially decreasing computing time.

Details

Currently, only C_NPMI and C_V are documented. The implementation follows Röder & al. (2015). For C_NPMI, the sliding window is 10 whereas it is 110 for C_V.

Value

A vector or matrix containing the coherence score of each topic.

Author(s)

Olivier Delmarcelle

References

Röder, M., Both, A., & Hinneburg, A. (2015). Exploring the Space of Topic Coherence Measures. In Proceedings of the Eighth ACM International Conference on Web Search and Data Mining, 399-–408.

Compute scores using the Picault-Renault lexicon

Description

Computes Monetary Policy and Economic Condition scores using the Picault-Renault lexicon for central bank communication.

Usage

compute_PicaultRenault_scores(x, min_ngram = 2, return_dfm = FALSE)

Arguments

x

a quanteda::corpus object.

min_ngram

the minimum length of n-grams considered in the computation

return_dfm

if TRUE, returns the scaled word-per-document score under two quanteda::dfm, on for the Monetary Policy and one for the Economic Condition categories. If FALSE, returns the sum of all word scores per document.

Details

The computation is done on a per-document basis, such as each document is scored with a value between -1 and 1. This is relevant to the computation of the denominator of the score.

It is possible to compute the score for paragraphs and sentences for a quanteda::corpus segmented using quanteda::corpus_reshape. Segmenting a corpus using quanteda's helpers retain track to which document each paragraph/sentence belong. However, in that case, it is possible that paragraphs or sentences are scored outside the (-1,1) interval. In any case, the of the paragraph/sentences scores averaged over documents will be contained in the (-1,1) interval.

Value

A matrix with two columns, indicating respectively the MP (Monetary Policy) and EC (Economic Condition) scores of each document.

References

Picault, M. & Renault, T. (2017). Words are not all created equal: A new measure of ECB communication. Journal of International Money and Finance, 79, 136–156. doi:10.1016/j.jimonfin.2017.09.005

Examples

# on documents
docs <- quanteda::corpus_reshape(ECB_press_conferences, "documents")
compute_PicaultRenault_scores(docs)

# on paragraphs
compute_PicaultRenault_scores(ECB_press_conferences)

Estimate a topic model

Description

This function is used to estimate a topic model created by LDA(), JST() or rJST(). In essence, this function iterates a Gibbs sampler MCMC.

Usage

## S3 method for class 'sentopicmodel'
fit(
  object,
  iterations = 100,
  nChains = 1,
  displayProgress = TRUE,
  computeLikelihood = TRUE,
  seed = NULL,
  ...
)

## S3 method for class 'multiChains'
fit(
  object,
  iterations = 100,
  nChains = NULL,
  displayProgress = TRUE,
  computeLikelihood = TRUE,
  seed = NULL,
  ...
)

Arguments

object

a model created with the LDA(), JST() or rJST() function.

iterations

the number of iterations by which the model should be fitted.

nChains

if set above 1, the model will be fitted multiple times from various starting positions. Latent variables will be re-initialized if object has not been fitted before.

displayProgress

if TRUE, a progress bar will be displayed indicating the progress of the computation. When nChains is greater than 1, this requires the package progressr and optionally progress.

computeLikelihood

if set to FALSE, does not compute the likelihood at each iteration. This can slightly decrease the computing time.

seed

for reproducibility, a seed can be provided.

...

arguments passed to other methods. Not used.

Value

a sentopicmodel of the relevant model class if nChains is unspecified or equal to 1. A multiChains object if nChains is greater than 1.

Parallelism

Examples

model <- rJST(ECB_press_conferences_tokens)
fit(model, 10)

# -- Parallel computation --
require(future.apply)
future::plan("multisession", workers = 2) # Set up 2 workers
fit(model, 10, nChains = 2)

future::plan("sequential") # Shut down workers

Download press conferences from the European Central Bank

Description

This helper function automatically retrieve the full data set of press conferences made available by the ECB. It implements a number of pre-processing steps used to remove the Q&A section from the text.

Usage

get_ECB_press_conferences(
  years = 1998:2021,
  language = "en",
  data.table = TRUE
)

Arguments

years

the years for which press conferences should be retrieved

language

the language in which press conferences should be retrieved

data.table

if TRUE, returns a data.table::data.table. Otherwise, return a list in which each element is a press conference.

Value

Depending on the arguments, returns either a data.frame or a quanteda::tokens object containing press conferences of the ECB.

Download and pre-process speeches from the European Central Bank

Description

This helper function automatically retrieve the full data set of speeches made available by the ECB. In addition, it implements a number of pre-processing steps that may be turned on or off as needed.

Usage

get_ECB_speeches(
  filter_english = TRUE,
  clean_footnotes = TRUE,
  compute_sentiment = TRUE,
  tokenize_w_POS = FALSE
)

Arguments

filter_english

if TRUE, attempts to select English speeches only using textcat::textcat().

clean_footnotes

if TRUE, attempts to clean footnotes from speeches texts using some regex patterns.

compute_sentiment

if TRUE, computes the sentiment of each speech using sentometrics::compute_sentiment() with the the Loughran & McDonald lexicon.

tokenize_w_POS

if TRUE, tokenizes and apply Part-Of-Speech tagging with spacyr::spacy_parse(). Nouns, adjectives and proper nouns are then extracted from the parsed speeches to form a tokens object.

Value

Depending on the arguments, returns either a data.frame or a quanteda::tokens object containing speeches of the ECB.

Replacement generic for `data.table::melt()`

Description

As of the CRAN release of the 1.14.8 version of data.table, the data.table::melt() function is not a generic. This function aims to temporary provide a generic to this function, so that melt.sentopicmodel() can be effectively dispatched when used. Expect this function to disappear shortly after the release of data.table 1.14.9.

Usage

melt(data, ...)

Arguments

data

an object to melt

...

arguments passed to other methods

Value

An unkeyed data.table containing the molten data.

Melt for sentopicmodels

Description

This function extracts the estimated document mixtures from a topic model and returns them in a long data.table::data.table format.

Usage

## S3 method for class 'sentopicmodel'
melt(data, ..., include_docvars = FALSE)

Arguments

data

a model created from the LDA(), JST() or rJST() function and estimated with fit()

...

not used

include_docvars

if TRUE, the melted result will also include the docvars stored in the tokens object provided at model initialization

Value

A data.table::data.table in the long format, where each line is the estimated proportion of a single topic/sentiment for a document. For JST and rJST models, the probability is also decomposed into 'L1' and 'L2' layers, representing the probability at each layer of the topic-sentiment hierarchy.

Author(s)

Olivier Delmarcelle

Examples

# only returns topic proportion for LDA models
lda <- LDA(ECB_press_conferences_tokens)
lda <- fit(lda, 10)
melt(lda)

# includes sentiment for JST and rJST models
jst <- JST(ECB_press_conferences_tokens)
jst <- fit(jst, 10)
melt(jst)

Merge topics into fewer themes

Description

This operation is especially useful for the analysis of the model's output, by grouping together topics that share a common theme.

Usage

mergeTopics(x, merging_list)

Arguments

x

a LDA() or rJST() model.

merging_list

a list where each element is an integer vector containing the indices of topics to be merged. If named, the list's names become the label of the aggregated themes.

Details

Topics are aggregated at the word assignment level. New document-topic and topic-word probabilities are derived from the aggregated assignments.

Note that the output of this function does not constitute an estimated topic model, but merely an aggregation to ease the analysis. It is not advised to use fit() on the merged topic model as it will radically affect the content and proportions of the new themes.

Value

A LDA() or rJST() model with the merged topics.

Examples

lda <- LDA(ECB_press_conferences_tokens, K = 5)
lda <- fit(lda, 100)
merging_list <- list(
  c(1,5),
  2:4
)
mergeTopics(lda, merging_list)

# also possible with a named list
merging_list2 <- list(
  mytheme_1 = c(1,5),
  mytheme_2 = 2:4
)
merged <- mergeTopics(lda, merging_list2)
sentopics_labels(merged)

# implemented for rJST
rjst <- rJST(ECB_press_conferences_tokens, lexicon = LoughranMcDonald)
rjst <- fit(rjst, 100)
mergeTopics(rjst, merging_list2)

Plot the distances between topic models (chains)

Description

Plot the results of chainsDistance(x) using multidimensional scaling. See chainsDistances() for details on the distance computation and stats::cmdscale() for the implementation of the multidimensional scaling.

Usage

## S3 method for class 'multiChains'
plot(
  x,
  ...,
  method = c("euclidean", "hellinger", "cosine", "minMax", "naiveEuclidean",
    "invariantEuclidean")
)

Arguments

x

a valid multiChains object, obtained through the estimation of a topic model using fit() and the argument nChains greater than 1.

...

not used

method

the method used to measure the distance between chains.

Value

Invisibly, the coordinates of each topic model resulting from the multidimensional scaling.

Examples

models <- LDA(ECB_press_conferences_tokens)
models <- fit(models, 10, nChains = 5)
plot(models)

Plot a topic model using Plotly

Description

Summarize and plot a sentopics model using a sunburst chart from the plotly::plotly library.

Usage

## S3 method for class 'sentopicmodel'
plot(x, nWords = 15, layers = 3, sort = FALSE, ...)

Arguments

x

a model created from the LDA(), JST() or rJST() function and estimated with fit()

nWords

the number of words per topic/sentiment to display in the outer layer of the plot

layers

specifies the number of layers for the sunburst chart. This will restrict the output to the layers uppermost levels of the chart. For example, setting layers = 1 will only display the top level of the hierarchy (topics for an LDA model).

sort

if TRUE, sorts the plotted topics in a decreasing frequency.

...

not used

Value

A plotly sunburst chart.

Examples

lda <- LDA(ECB_press_conferences_tokens)
lda <- fit(lda, 100)
plot(lda, nWords = 5)

# only displays the topic proportions
plot(lda, layers = 1)

Print method for sentopics models

Description

Print methods for sentopics models. Once per session (or forced by using extended = TRUE), it lists the most important function related to sentopics models.

Usage

## S3 method for class 'sentopicmodel'
print(x, extended = FALSE, ...)

## S3 method for class 'rJST'
print(x, extended = FALSE, ...)

## S3 method for class 'LDA'
print(x, extended = FALSE, ...)

## S3 method for class 'JST'
print(x, extended = FALSE, ...)

Arguments

x

the model to be printed

extended

if TRUE, extends the print to include some helpful related functions. Automatically displayed once per session.

...

not used

Value

No return value, called for side effects (printing).

Compute the topic or sentiment proportion time series

Description

Aggregate the topical or sentiment proportions at the document level into time series.

Usage

proportion_topics(
  x,
  period = c("year", "quarter", "month", "day", "identity"),
  rolling_window = 1,
  complete = TRUE,
  plot = c(FALSE, TRUE, "silent"),
  plot_ridgelines = TRUE,
  as.xts = TRUE,
  ...
)

plot_proportion_topics(
  x,
  period = c("year", "quarter", "month", "day"),
  rolling_window = 1,
  complete = TRUE,
  plot_ridgelines = TRUE,
  ...
)

Arguments

x

a LDA(), JST() or rJST() model populated with internal dates and/or internal sentiment.

period

the sampling period within which the sentiment of documents will be averaged. period = "identity" is a special case that will return document-level variables before the aggregation happens. Useful to rapidly compute topical sentiment at the document level.

rolling_window

if greater than 1, determines the rolling window to compute a moving average of sentiment. The rolling window is based on the period unit and rely on actual dates (i.e, is not affected by unequally spaced data points).

complete

if FALSE, only compute proportions at the upper level of the topic model hierarchy (topics for rJST and sentiment for JST). No effect on LDA models.

plot

if TRUE, prints a plot of the time series and attaches it as an attribute to the returned object. If 'silent', do not print the plot but still attaches it as an attribute.

plot_ridgelines

if TRUE, time series are plotted as ridgelines. Requires ggridges package installed. If FALSE, the plot will use only standards ggplot2 functions. If the argument is missing and the package ggridges is not installed, this will quietly switch to a ggplot2 output.

as.xts

if TRUE, returns an xts::xts object. Otherwise, returns a data.frame.

...

other arguments passed on to zoo::rollapply() or mean() and sd().

Value

A time series of proportions, stored as an xts::xts object or as a data.frame.

Examples

lda <- LDA(ECB_press_conferences_tokens)
lda <- fit(lda, 100)
proportion_topics(lda)

# plot shortcut
plot_proportion_topics(lda, period = "month", rolling_window = 3)
# with or without ridgelines
plot_proportion_topics(lda, period = "month", plot_ridgelines = FALSE)

# also available for rJST and JST models
jst <- JST(ECB_press_conferences_tokens, lexicon = LoughranMcDonald)
jst <- fit(jst, 100)
# including both layers
proportion_topics(jst)
# or not
proportion_topics(jst, complete = FALSE)

Create a Reversed Joint Sentiment/Topic model

Description

This function initialize a Reversed Joint Sentiment/Topic model.

Usage

rJST(x, ...)

## Default S3 method:
rJST(
  x,
  lexicon = NULL,
  K = 5,
  S = 3,
  alpha = 1,
  gamma = 5,
  beta = 0.01,
  alphaCycle = 0,
  gammaCycle = 0,
  ...
)

## S3 method for class 'LDA'
rJST(x, lexicon = NULL, S = 3, gamma = 5, ...)

Arguments

x

tokens object containing the texts. A coercion will be attempted if x is not a tokens.

...

not used

lexicon

a quanteda dictionary with positive and negative categories

K

the number of topics

S

the number of sentiments

alpha

the hyperparameter of topic-document distribution

gamma

the hyperparameter of sentiment-document distribution

beta

the hyperparameter of vocabulary distribution

alphaCycle

integer specifying the cycle size between two updates of the hyperparameter alpha

gammaCycle

integer specifying the cycle size between two updates of the hyperparameter alpha

Details

Value

An S3 list containing the model parameter and the estimated mixture. This object corresponds to a Gibbs sampler estimator with zero iterations. The MCMC can be iterated using the fit() function.

tokens is the tokens object used to create the model
vocabulary contains the set of words of the corpus
it tracks the number of Gibbs sampling iterations
za is the list of topic assignment, aligned to the tokens object with padding removed
logLikelihood returns the measured log-likelihood at each iteration, with a breakdown of the likelihood into hierarchical components as attribute

The topWords() function easily extract the most probables words of each topic/sentiment.

Author(s)

Olivier Delmarcelle

References

Lin, C. and He, Y. (2009). Joint sentiment/topic model for sentiment analysis. In Proceedings of the 18th ACM conference on Information and knowledge management, 375–384.

Lin, C., He, Y., Everson, R. and Ruger, S. (2012). Weakly Supervised Joint Sentiment-Topic Detection from Text. IEEE Transactions on Knowledge and Data Engineering, 24(6), 1134–-1145.

Examples

# simple rJST model
rJST(ECB_press_conferences_tokens)

# estimating a rJST model including lexicon
rjst <- rJST(ECB_press_conferences_tokens, lexicon = LoughranMcDonald)
rjst <- fit(rjst, 100)

# from an LDA model:
lda <- LDA(ECB_press_conferences_tokens)
lda <- fit(lda, 100)

# creating a rJST model out of it
rjst <- rJST(lda, lexicon = LoughranMcDonald)
# topic proportions remain identical
identical(lda$theta, rjst$theta)
# model should be iterated to estimate sentiment proportions
rjst <- fit(rjst, 100)

Objects exported from other packages

Description

These objects are imported from other packages. Follow the links below to see their documentation.

generics: fit
quanteda: as.tokens, docvars, tokens

Re-initialize a topic model

Description

This function is used re-initialize a topic model, as if it was created from LDA(), JST() or another model. The re-initialized model retains its original parameter specification.

Usage

reset(object)

Arguments

object

a model created from the LDA(), JST() or rJST() function and estimated with fit()

Value

a sentopicmodel of the relevant model class, with the iteration count reset to zero and re-initialized assignment of latent variables.

Author(s)

Olivier Delmarcelle

Examples

model <- LDA(ECB_press_conferences_tokens)
model <- fit(model, 10)
reset(model)

Breakdown the sentiment into topical components

Description

Break down the sentiment series obtained with sentiment_series() into topical components. Sentiment is broken down at the document level using estimated topic proportions, then processed to create a time series and its components.

Usage

sentiment_breakdown(
  x,
  period = c("year", "quarter", "month", "day", "identity"),
  rolling_window = 1,
  scale = TRUE,
  scaling_period = c("1900-01-01", "2099-12-31"),
  plot = c(FALSE, TRUE, "silent"),
  as.xts = TRUE,
  ...
)

plot_sentiment_breakdown(
  x,
  period = c("year", "quarter", "month", "day"),
  rolling_window = 1,
  scale = TRUE,
  scaling_period = c("1900-01-01", "2099-12-31"),
  ...
)

Arguments

x

a LDA() or rJST() model populated with internal dates and/or internal sentiment.

period

rolling_window

scale

if TRUE, the resulting time series will be scaled to a mean of zero and a standard deviation of 1. This argument also has the side effect of attaching scaled sentiment values as docvars to the input object with the ⁠_scaled⁠ suffix.

scaling_period

the date range over which the scaling should be applied. Particularly useful to normalize only the beginning of the time series.

plot

if TRUE, prints a plot of the time series and attaches it as an attribute to the returned object. If 'silent', do not print the plot but still attaches it as an attribute.

as.xts

if TRUE, returns an xts::xts object. Otherwise, returns a data.frame.

...

other arguments passed on to zoo::rollapply() or mean() and sd().

Details

The sentiment is broken down at the sentiment level assuming the following composition:

s = \sum^K_{i=1} s_i \times \theta_i

, where s_i is the sentiment of topic i and theta_i the proportion of topic i in a given document. For an LDA model, the sentiment of each topic is considered equal to the document sentiment (i.e. s_i = s \forall i \in K). The topical sentiment attention, defined by s*_i = s_i \times \theta_i represent the effective sentiment conveyed by a topic in a document. The topical sentiment attention of all documents in a period are averaged to compute the breakdown of the sentiment time series.

Value

A time series of sentiment, stored as an xts::xts object or as a data.frame.

Examples

lda <- LDA(ECB_press_conferences_tokens)
lda <- fit(lda, 100)
sentiment_breakdown(lda)

# plot shortcut
plot_sentiment_breakdown(lda)

# also available for rJST models (with topic-level sentiment)
rjst <- rJST(ECB_press_conferences_tokens, lexicon = LoughranMcDonald)
rjst <- fit(rjst, 100)
sentopics_sentiment(rjst, override = TRUE)
plot_sentiment_breakdown(rjst)

Compute a sentiment time series

Description

Compute a sentiment time series based on the internal sentiment and dates of a sentopicmodel. The time series computation supports multiple sampling period and optionally allow computing a moving average.

Usage

sentiment_series(
  x,
  period = c("year", "quarter", "month", "day"),
  rolling_window = 1,
  scale = TRUE,
  scaling_period = c("1900-01-01", "2099-12-31"),
  as.xts = TRUE,
  ...
)

Arguments

x

a LDA(), JST() or rJST() model populated with internal dates and/or internal sentiment.

period

rolling_window

scale

scaling_period

the date range over which the scaling should be applied. Particularly useful to normalize only the beginning of the time series.

as.xts

if TRUE, returns an xts::xts object. Otherwise, returns a data.frame.

...

other arguments passed on to zoo::rollapply() or mean() and sd().

Value

A time series of sentiment, stored as an xts::xts or data.frame.

Examples

lda <- LDA(ECB_press_conferences_tokens)
series <- sentiment_series(lda, period = "month")

# JST and rJST models can use computed sentiment from the sentiment layer,
# but the model must be estimated first.
rjst <- rJST(ECB_press_conferences_tokens, lexicon = LoughranMcDonald)
sentiment_series(rjst)

sentopics_sentiment(rjst) <- NULL ## remove existing sentiment
rjst <- fit(rjst, 10) ## estimating the model is then needed
sentiment_series(rjst)

# note the presence of both raw and scaled sentiment values
# in the initial object
sentopics_sentiment(lda)
sentopics_sentiment(rjst)

Compute time series of topical sentiments

Description

Derive topical time series of sentiment from a LDA() or rJST() model. The time series are created by leveraging on estimated topic proportions and internal sentiment (for LDA models) or topical sentiment (for rJST models).

Usage

sentiment_topics(
  x,
  period = c("year", "quarter", "month", "day", "identity"),
  rolling_window = 1,
  scale = TRUE,
  scaling_period = c("1900-01-01", "2099-12-31"),
  plot = c(FALSE, TRUE, "silent"),
  plot_ridgelines = TRUE,
  as.xts = TRUE,
  ...
)

plot_sentiment_topics(
  x,
  period = c("year", "quarter", "month", "day"),
  rolling_window = 1,
  scale = TRUE,
  scaling_period = c("1900-01-01", "2099-12-31"),
  plot_ridgelines = TRUE,
  ...
)

Arguments

x

a LDA() or rJST() model populated with internal dates and/or internal sentiment.

period

rolling_window

scale

scaling_period

the date range over which the scaling should be applied. Particularly useful to normalize only the beginning of the time series.

plot

if TRUE, prints a plot of the time series and attaches it as an attribute to the returned object. If 'silent', do not print the plot but still attaches it as an attribute.

plot_ridgelines

as.xts

if TRUE, returns an xts::xts object. Otherwise, returns a data.frame.

...

other arguments passed on to zoo::rollapply() or mean() and sd().

Details

A topical sentiment is computed at the document level for each topic. For an LDA model, the sentiment of each topic is considered equal to the document sentiment (i.e. s_i = s \forall i \in K). For a rJST model, these result from the proportions in the sentiment layer under each topic. To compute the topical time series, the topical sentiment of all documents in a period are aggregated according to their respective topic proportion. For example, for a given topic, the topical sentiment in period t is computed using:

s_t = \frac{\sum_{d = 1}^D s_d \times \theta_d}{\sum_{d = 1}^D \theta_d}

, where s_d is the sentiment of the topic in document d and theta_d the topic proportion in a document d.

Value

an xts::xts or data.frame containing the time series of topical sentiments.

Examples

lda <- LDA(ECB_press_conferences_tokens)
lda <- fit(lda, 100)
sentiment_topics(lda)

# plot shortcut
plot_sentiment_topics(lda, period = "month", rolling_window = 3)
# with or without ridgelines
plot_sentiment_topics(lda, period = "month", plot_ridgelines = FALSE)

# also available for rJST models with internal sentiment computation
rjst <- rJST(ECB_press_conferences_tokens, lexicon = LoughranMcDonald)
rjst <- fit(rjst, 100)
sentopics_sentiment(rjst, override = TRUE)
sentiment_topics(rjst)

Create a sentopic model

Description

The set of functions LDA(), JST(), rJST() and sentopicmodel() are all wrappers to an unified C++ routine and attempt to replicate their corresponding model. This function is the lower level wrapper to the C++ routine.

Usage

sentopicmodel(
  x,
  lexicon = NULL,
  L1 = 5,
  L2 = 3,
  L1prior = 1,
  L2prior = 5,
  beta = 0.01,
  L1cycle = 0,
  L2cycle = 0,
  reversed = TRUE
)

Arguments

x

tokens object containing the texts. A coercion will be attempted if x is not a tokens.

lexicon

a quanteda dictionary with positive and negative categories

L1

the number of labels in the first document mixture layer

L2

the number of labels in the second document mixture layer

L1prior

the first layer hyperparameter of document mixtures

L2prior

the second layer hyperparameter of document mixtures

beta

the hyperparameter of vocabulary distribution

L1cycle

integer specifying the cycle size between two updates of the hyperparameter L1prior

L2cycle

integer specifying the cycle size between two updates of the hyperparameter L2prior

reversed

indicates on which dimension should lexicon apply. When reversed=FALSE, the lexicon is applied on the first layer of the document mixture (as in a JST model). When reversed=TRUE, the lexicon is applied to the second layer of the document mixture (as in a reversed-JST model).

Value

An S3 list containing the model parameter and the estimated mixture. This object corresponds to a Gibbs sampler estimator with zero iterations. The MCMC can be iterated using the fit() function.

tokens is the tokens object used to create the model
vocabulary contains the set of words of the corpus
it tracks the number of Gibbs sampling iterations
za is the list of topic assignment, aligned to the tokens object with padding removed
logLikelihood returns the measured log-likelihood at each iteration, with a breakdown of the likelihood into hierarchical components as attribute

The topWords() function easily extract the most probables words of each topic/sentiment.

Author(s)

Olivier Delmarcelle

Examples

LDA(ECB_press_conferences_tokens)
rJST(ECB_press_conferences_tokens, lexicon = LoughranMcDonald)

Internal conversions between sentopics models.

Description

Internal conversions between sentopics models.

Usage

as.sentopicmodel(x)

as.rJST(x)

as.JST(x)

Arguments

x

A sentopics model

Value

A sentopics model of the relevant class

Internal date

Description

Extract or replace the internal dates of a sentopicmodel. The internal dates are used to create time series using the functions sentiment_series() or sentiment_topics(). Dates should be provided by using sentopics_date(x) <- value or by storing a '.date' docvars in the tokens object used to create the model.

Usage

sentopics_date(x, include_docvars = FALSE)

sentopics_date(x) <- value

Arguments

x

a sentopicmodel created from the LDA(), JST(), rJST() or sentopicmodel() function

include_docvars

if TRUE the function will return all docvars stored in the internal tokens object of the model

value

a Date-coercible vector of dates to input into the model.

Value

a data.frame with the stored date per document.

Note

The internal date is stored internally in the docvars of the topic model. This means that dates may also be accessed through the docvars() function, although this is discouraged.

Author(s)

Olivier Delmarcelle

Examples

# example dataset already contains ".date" docvar
docvars(ECB_press_conferences_tokens)
# dates are automatically stored in the sentopicmodel object
lda <- LDA(ECB_press_conferences_tokens)
sentopics_date(lda)

# dates can be removed or modified by the assignment operator
sentopics_date(lda) <- NULL
sentopics_date(lda) <- docvars(ECB_press_conferences_tokens, ".date")

Setting topic or sentiment labels

Description

Extract or replace the labels of a sentopicmodel. The replaced labels will appear in most functions dealing with the output of the sentomicmodel.

Usage

sentopics_labels(x, flat = TRUE)

sentopics_labels(x) <- value

Arguments

x

a sentopicmodel created from the LDA(), JST(), rJST() or sentopicmodel() function

flat

if FALSE, return a list of dimension labels instead of a character vector.

value

a list of future labels for the topic model. The list should be named and contain a character vector for each dimension to label. See the examples for a correct usage.

Value

a character vector of topic/sentiment labels.

Author(s)

Olivier Delmarcelle

Examples

# by default, sentopics_labels() generate standard topic names
lda <- LDA(ECB_press_conferences_tokens)
sentopics_labels(lda)

# to change labels, a named list must be provided
sentopics_labels(lda) <- list(
 topic = paste0("superTopic", 1:lda$K)
)
sentopics_labels(lda)

# using NULL remove labels
sentopics_labels(lda) <- NULL
sentopics_labels(lda)

# also works for JST/rJST models
jst <- JST(ECB_press_conferences_tokens)
sentopics_labels(jst) <- list(
  topic = paste0("superTopic", 1:jst$K),
  sentiment = c("negative", "neutral", "positive")
)
sentopics_labels(jst)

# setting flat = FALSE return a list or labels for each dimension
sentopics_labels(jst, flat = FALSE)

Internal sentiment

Description

Compute, extract or replace the internal sentiment of a sentopicmodel. The internal sentiment is used to create time series using the functions sentiment_series() or sentiment_topics(). If the input model contains a sentiment layer, sentiment can be computed directly from the output of the model. Otherwise, sentiment obtained externally should be added for each document.

Usage

sentopics_sentiment(
  x,
  method = c("proportional", "proportionalPol"),
  override = FALSE,
  quiet = FALSE,
  include_docvars = FALSE
)

sentopics_sentiment(x) <- value

Arguments

x

a sentopicmodel created from the LDA(), JST(), rJST() or sentopicmodel() function

method

the method used to compute sentiment, see "Methods" below. Ignored if an internal sentiment is already stored, unless override is TRUE.

override

by default, the function computes sentiment only if no internal sentiment is already stored within the sentopicmodel object. This avoid, for example, erasing externally provided sentiment. Set to TRUE to force computation of new sentiment values. Only useful for models with a sentiment layer.

quiet

if FALSE, print a message when internal sentiment is found.

include_docvars

if TRUE the function will return all docvars stored in the internal tokens object of the model

value

a numeric vector of sentiment to input into the model.

Details

The computed sentiment varies depending on the model. For LDA, sentiment computation is not possible.

For JST, the sentiment is computed on a per-document basis according to the document-level sentiment mixtures.

For a rJST model, a sentiment is computed for each topic, resulting in K sentiment values per document. In that case, the .sentiment column is an average of the K sentiment values, weighted by they respective topical proportions.

Value

A data.frame with the stored sentiment per document.

Methods

The function accepts two methods of computing sentiment:

proportional computes the difference between the estimated positive and negative proportions for each document (and possibly each topic).

positive - negative
proportionalPol computes the difference between positive and negative proportions, divided by the sum of positive and negative proportions. As a result, the computed sentiment lies within the (-1;1) interval.

\frac{positive - negative}{positive + negative}

Both methods will lead to the same result for a JST model containing only negative and positive sentiments.

Note

The internal sentiment is stored internally in the docvars of the topic model. This means that sentiment may also be accessed through the docvars() function, although this is discouraged.

Author(s)

Olivier Delmarcelle

Examples

# example dataset already contains ".sentiment" docvar
docvars(ECB_press_conferences_tokens)
# sentiment is automatically stored in the sentopicmodel object
lda <- LDA(ECB_press_conferences_tokens)
sentopics_sentiment(lda)

# sentiment can be removed or modified by the assignment operator
sentopics_sentiment(lda) <- NULL
sentopics_sentiment(lda) <- docvars(ECB_press_conferences_tokens, ".sentiment")

# for JST models, sentiment can be computed from the output of the model
jst <- JST(ECB_press_conferences_tokens, lexicon = LoughranMcDonald)
jst <- fit(jst, 100)
sentopics_sentiment(jst, override = TRUE) # replace existing sentiment

## for rJST models one sentiment value is computed by topic
rjst <- rJST(ECB_press_conferences_tokens, lexicon = LoughranMcDonald)
rjst <- fit(rjst, 100)
sentopics_sentiment(rjst, override = TRUE)

Extract the most representative words from topics

Description

Extract the top words in each topic/sentiment from a sentopicmodel.

Usage

topWords(
  x,
  nWords = 10,
  method = c("frequency", "probability", "term-score", "FREX"),
  output = c("data.frame", "plot", "matrix"),
  subset,
  w = 0.5
)

plot_topWords(
  x,
  nWords = 10,
  method = c("frequency", "probability", "term-score", "FREX"),
  subset,
  w = 0.5
)

Arguments

x

a sentopicmodel created from the LDA(), JST() or rJST()

nWords

the number of top words to extract

method

specify if a re-ranking function should be applied before returning the top words. See Details for a description of each method.

output

determines the output of the function

subset

allows to subset using a logical expression, as in subset(). Particularly useful to limit the number of observation on plot outputs. The logical expression uses topic and sentiment indices rather than their label. It is possible to subset on both topic and sentiment but adding a & operator between two expressions.

w

only used when method = "FREX". Determines the weight assigned to the exclusivity score at the expense of the frequency score.

Details

"frequency" ranks top words according to their frequency within a topic. This method also reports the overall frequency of each word. When returning a plot, the overall frequency is represented with a grey bar.

"probability" uses the estimated topic-word mixture \phi to rank top words.

"term-score" implements the re-ranking method from Blei and Lafferty (2009). This method down-weights terms that have high probability in all topics using the following score:

\text{term-score}_{k,v} = \phi_{k, v}\log\left(\frac{\phi_{k, v}}{\left(\prod^K_{j=1}\phi_{j,v}\right)^{\frac{1}{K}}}\right),

for topic k, vocabulary word v and number of topics K.

"FREX" implements the re-ranking method from Bischof and Airoldi (2012). This method used the weight w to balance between topic-word probability and topic exclusivity using the following score:

\text{FREX}_{k,v}=\left(\frac{w}{\text{ECDF}\left( \frac{\phi_{k,v}}{\sum_{j=1}^K\phi_{k,v}}\right)} + \frac{1-w}{\text{ECDF}\left(\phi_{k,v}\right)} \right),

for topic k, vocabulary word v, number of topics K and weight w, where \text{ECDF} is the empirical cumulative distribution function.

Value

The top words of the topic model. Depending on the output chosen, can result in either a long-style data.frame, a ggplot2 object or a matrix.

Author(s)

Olivier Delmarcelle

References

Blei, DM. and Lafferty, JD. (2009). Topic models.. In Text Mining, chapter 4, 101–124.

Bischof JM. and Airoldi, EM. (2012). Summarizing Topical Content with Word Frequency and Exclusivity.. In Proceedings of the 29th International Conference on International Conference on Machine Learning, ICML'12, 9–16.

Examples

model <- LDA(ECB_press_conferences_tokens)
model <- fit(model, 10)
topWords(model)
topWords(model, output = "matrix")
topWords(model, method = "FREX")
plot_topWords(model)
plot_topWords(model, subset = topic %in% 1:2)

jst <- JST(ECB_press_conferences_tokens)
jst <- fit(jst, 10)
plot_topWords(jst)
plot_topWords(jst, subset = topic %in% 1:2 & sentiment == 3)

Tools for joining sentiment and topic analysis (sentopics)

Description

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Author(s)

See Also

Corpus of press conferences from the European Central Bank

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Examples

Tokenized press conferences

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Examples

Create a Joint Sentiment/Topic model

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Examples

Create a Latent Dirichlet Allocation model

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Examples

Visualize a LDA model using LDAvis

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Examples

Loughran-McDonald lexicon

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Examples

Picault-Renault lexicon

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Examples

Regression dataset based on Picault & Renault (2017)

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Examples

Conversions from other packages to LDA

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Examples

Convert back a dfm to a tokens object

Description

Replacement generic for `data.table::melt()`