R: Random sample

sampleRandom {raster} | R Documentation

## 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)

[Package raster version 2.5-8 Index]