raster (version 3.6-30)

stretch: Stretch

Description

Linear stretch of values in a Raster object. Provide the desired output range (minv and maxv) and the lower and upper bounds in the original data, either as quantiles (if minq=0 and maxq=1 you use the minimum and maximum cell values), or as actual values (smin and smax; e.g. precomputed quantile values). If smin and smax are both not NA, minq and maxq are ignored.

Usage

# S4 method for Raster
stretch(x, minv=0, maxv=255, minq=0, maxq=1, smin=NA, smax=NA,
          samplesize=1000000, filename='', ...)

Value

Raster

Arguments

x

Raster object

minv

numeric >= 0 and smaller than maxv. lower bound of stretched value

maxv

numeric <= 255 and larger than maxv. upper bound of stretched value

minq

numeric >= 0 and smaller than maxq. lower quantile bound of original value. Ignored if smin is supplied

maxq

numeric <= 1 and larger than minq. upper quantile bound of original value. Ignored if smax is supplied

smin

numeric < smax. user supplied lower value for the layers, to be used instead of a quantile computed by the function itself

smax

numeric > smin. user supplied upper value for the layers, to be used instead of a quantile computed by the function itself

samplesize

numeric > 1. If samplesize < ncell(x), a regular sample of samplesize is taken from x to compute the quantiles (to speed things up)

filename

character. Filename for the output Raster object (optional)

...

additional arguments as for writeRaster

See Also

stretch argument in plotRGB

Examples

r <- raster(nc=10, nr=10)
values(r) <- rep(1:2, 50)
stretch(r)
s <- stack(r, r*2)
stretch(s)