Pipe operator

Description

See magrittr::pipe for details.

Usage

lhs %>% rhs

Convert a Raster to a data frame.

Description

Generate a data frame version of any raster object. Use the arguments 'cell', 'dim', 'split_date' and 'value' to control the columns that are included in the output.

Usage

## S3 method for class 'BasicRaster'
as_tibble(
  x,
  cell = TRUE,
  dim = nlayers(x) > 1L,
  value = TRUE,
  split_date = FALSE,
  xy = FALSE,
  ...
)

Arguments

Details

If the raster has only one layer, the slice index is not added. Use 'dim = FALSE' to not include the slice index value.

Value

a data frame (tibble) with columns:

• cellvalue the actual value of the raster cell

• cellindex the index of the cell (numbered from 1 to ncell() in the raster way).

Columns cellindex or cellvalue may be omitted if either or both of cell and/or value are FALSE, respectively

Other columns might be included depending on the properties of the raster and the arguments to the function:

• year,month,day if split_date is TRUE

• x,y if xy is TRUE

• dimindex if the input has more than 1 layer and dim is TRUE.

Examples

## basic data frame version of a basic raster
as_tibble(raster::raster(volcano))

## data frame with time column since raster has that set
r <- raster::raster(volcano)
br <- raster::brick(r, r)
as_tibble(raster::setZ(br, Sys.Date() + 1:2), cell = TRUE)

Extract cell numbers from a Raster object.

Description

Provide the 'cellnumbers' capability of raster::extract and friends directly, returning a data frame of query-object identifiers 'object_' and the cell number.

Usage

cellnumbers(x, query, ...)

## Default S3 method:
cellnumbers(x, query, ...)

## S3 method for class 'SpatialLines'
cellnumbers(x, query, ...)

## S3 method for class 'sfc'
cellnumbers(x, query, ...)

## S3 method for class 'sf'
cellnumbers(x, query, ...)

Arguments

Details

Raster data is inherently 2-dimensional, with a time or 'level' dimension treated like a layers of these 2D forms. The 'raster' package cell number is counted from 1 at the top-left, across the rows and down. This corresponds the the standard "raster graphics" convention used by 'GDAL' and the 'sp' package, and many other implementations. Note that this is different to the convention used by the graphics::image function.

Currently this function only operates as if the input is a single layer objects, it's not clear if adding an extra level of grouping for layers would be sensible.

Value

a data frame (tibble) with columns

• object_ - the object ID (what row is it from the spatial object)

• cell_ - the cell number of the raster

Examples

library(raster)
library(dplyr)
r <- raster(volcano) %>% aggregate(fact = 4)
cellnumbers(r, rasterToContour(r, level = 120))
library(dplyr)

cr <- cut(r,  pretty(values(r)))

suppressWarnings(tt <- cellnumbers(cr, polycano))
library(dplyr)
tt %>% mutate(v = extract(r, cell_)) %>% 
group_by(object_) %>% 
summarize(mean(v)) 
head(pretty(values(r)), -1)

Decimate swiftly and ruthlessly

Description

Reduce the resolution of a raster by ruthless decimation.

Usage

decimate(x, dec = 10)

Arguments

Details

This is fast, it's just fast extraction with no care taken for utility purposes when you need to reduce the detail.

Value

raster layer

Examples

library(raster)
plot(decimate(raster(volcano)))
contour(raster(volcano), add = TRUE)

Sea surface temperature data.

Description

A smoothed subset of GHRSST.

Format

A raster created GHRSST data and raster smoothing.

Details

See "data-raw/ghrsst.R" and "data-raw/ghrsst-readme.txt" for details.

sst_regions is a simple polygon region layer to sit over the SST data.

Examples

library(raster)
plot(ghrsst, col = hcl.colors(12, "YlOrRd", rev = TRUE))
plot(sst_regions, add = TRUE, col = NA)
cellnumbers(ghrsst, sst_regions) 

Index extent

Description

Extent in index space.

Usage

index_extent(x, ex)

Arguments

Details

Convert a geographic extent into purely index space.

Value

extent object

Examples

## the index extent is the rows/cols
index_extent(raster::raster(volcano), raster::extent(0, 1, 0, 1))

index_extent(raster::raster(volcano), raster::extent(0, 1, 0, .5))

Optimally interpolated SST in near-native form.

Description

See data-raw/oisst.R in the source repository. The file was avhrr-only-v2.20170729.nc, its extent -180, 180, -90, 90 with dimensions 1440x720 in the usual raster configuration.

Format

A data frame of sst values created from OISST data.

Examples

oisst

The raster volcano as polygons.

Description

See data-raw/rastercano.r in the source repository.

Format

A sp::SpatialPolygonsDataFrame with variables: volcano_elevation.

Examples

exists("polycano")

The raster volcano.

Description

See data-raw/rastercano.r in the source repository.

Format

A raster created from the volcano data.

Examples

library(raster)
plot(rastercano)

Sharkcano, the shark and the volcano.

Description

This is just a free image off the internet. The image was read in and all non-essential items dropped. The dimensions in raster::raster terms is stored in attr(sharkcano, "rasterdim").

Format

A data frame with 117843 rows and 2 variables:

cell_

integer, cell index

byte

integer, byte value of shark image pixels

These are cell values on a grid that is 648x958.

References

This is the small version from here, see script in data-raw/sharkcano.r http://www.freestockphotos.biz/stockphoto/16214 Thanks to @jennybc for pointers on finding free stuff: https://github.com/jennybc/free-photos

Examples

library(raster)
rd <- attr(sharkcano, "rasterdim")
rastershark <- raster(matrix(NA_integer_, rd[1], rd[2]))
rastershark[sharkcano$cell_] <- sharkcano$byte  ## byte, heh
## I present to you, Sharkcano!  (Just wait for the 3D version, Quadshark).
plot(rastercano)
contour(rastershark, add = TRUE, labels = FALSE)
plot(rastershark, col = "black")
## another way
plot(rastercano)
points(xyFromCell(rastershark, sharkcano$cell_), pch = ".")

Tabular tools for raster

Description

Extract and index with raster tidy tools for raster.

Details

Tabularaster includes these main functions.