gridSample
From dismo v1.14
by Robert Hijmans
Stratified regular sample on a grid
Sample points from xy, using a grid (raster) as stratification. Up to n points are sampled from each stratum (cell). For "chessboard" sampling (i.e. sampling from half the cells), use the argument chess='black'
, or chess='white'
.
 Keywords
 spatial
Usage
gridSample(xy, r, n=1, chess='')
Arguments
 xy
 A two column matrix or data.frame with x and y coordinates (or longitude and latitude), or a SpatialPoints* object
 r
 Raster* object
 n
 Maximum number of samples per cell
 chess
 Character. '', 'black', or 'white'. If 'black' or 'white', "chessboard" sampling is used. I.e. only the 'white' fields, or only the 'black' fields are sampled. Cell number 1 (the upper left corner of
r
) is white.
Value

A two column matrix with x and y coordinates (or longitude and latitude)
See Also
Examples
x < rnorm(1000, 10, 5)
y < rnorm(1000, 50, 5)
xy < cbind(x,y)
res < 5
r < raster(extent(range(xy[,1]), range(xy[,2])) + res)
res(r) < res
samp < gridSample(xy, r, n=1)
plot(xy, cex=0.1)
points(samp, pch='x', col='red')
Community examples
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