cellStats: Statistics across cells

In raster: Geographic Data Analysis and Modeling

Statistics across cells

Description

Compute statistics for the cells of each layer of a Raster* object. In the raster package, functions such as max, min, and mean, when used with Raster* objects as argument, return a new Raster* object (with a value computed for each cell). In contrast, cellStats returns a single value, computed from the all the values of a layer. Also see layerStats

Usage

## S4 method for signature 'RasterLayer'
cellStats(x, stat='mean', na.rm=TRUE, asSample=TRUE, ...)

## S4 method for signature 'RasterStackBrick'
cellStats(x, stat='mean', na.rm=TRUE, asSample=TRUE, ...)

Arguments

x	Raster* object
stat	The function to be applied. See Details
na.rm	Logical. Should NA values be removed?
asSample	Logical. Only relevant for stat=sd in which case, if TRUE, the standard deviation for a sample (denominator is n-1) is computed, rather than for the population (denominator is n)
...	Additional arguments

Details

cellStats will fail (gracefully) for very large Raster* objects except for a number of known functions: sum, mean, min, max, sd, 'skew' and 'rms'. 'skew' (skewness) and 'rms' (Root Mean Square) must be supplied as a character value (with quotes), the other known functions may be supplied with or without quotes. For other functions you could perhaps use a sample of the RasterLayer that can be held in memory (see sampleRegular )

Value

Numeric

See Also

freq, quantile, minValue, maxValue, setMinMax

Examples

r <- raster(nrow=18, ncol=36)
values(r) <- runif(ncell(r)) * 10
# works for large files
cellStats(r, 'mean')
# same, but does not work for very large files
cellStats(r, mean)
# multi-layer object
cellStats(brick(r,r), mean)

raster documentation built on Oct. 3, 2024, 1:08 a.m.