strech function

Stretch

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.

## S4 method for signature '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 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

Returns

Raster

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)