sampleRandom: Random sample

In raster: Geographic Data Analysis and Modeling

Random sample

Description

Take a random sample from the cell values of a Raster* object (without replacement).

Usage

## S4 method for signature 'Raster'
sampleRandom(x, size, na.rm=TRUE, ext=NULL, 
    cells=FALSE, rowcol=FALSE, xy=FALSE, sp=FALSE, asRaster=FALSE, ...)

Arguments

x	Raster* object
size	positive integer giving the number of items to choose
na.rm	logical. If TRUE (the default), NA values are removed from random sample
ext	Extent object. To limit regular sampling to the area within the extent
cells	logical. If TRUE, sampled cell numbers are also returned
rowcol	logical. If TRUE, sampled row and column numbers are also returned
xy	logical. If TRUE, coordinates of sampled cells are also returned
sp	logical. If TRUE, a SpatialPointsDataFrame is returned
asRaster	logical. If TRUE, a Raster* object is returned with random cells with values, all other cells with NA
...	Additional arguments as in writeRaster. Only relevant when asRaster=TRUE

Details

With argument na.rm=TRUE, the returned sample may be smaller than requested

Value

A vector, matrix (if cells=TRUE or x is a multi-layered object), or a SpatialPointsDataFrame (if sp=TRUE )

See Also

sampleRegular, sampleStratified

Examples

 r <- raster(system.file("external/test.grd", package="raster"))
 sampleRandom(r, size=10)
 s <- stack(r, r)
 sampleRandom(s, size=5, cells=TRUE, sp=TRUE)

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