raster (version 3.1-5)

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 quintiles (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='', ...)

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 quintile bound of original value. Ignored if qmin is supplied

maxq

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

smin

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

smax

numeric > smin. user supplied upper value for the layers, to be used instead of a quintile 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

Value

Raster

See Also

stretch argument in plotRGB

Examples

# NOT RUN {
r <- raster(nc=10, nr=10)
values(r) <- rep(1:2, 50)
stretch(r)
s <- stack(r, r*2)
stretch(s)
# }