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='', ...)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 |
Raster
stretch argument in plotRGB
r <- raster(nc=10, nr=10) values(r) <- rep(1:2, 50) stretch(r) s <- stack(r, r*2) stretch(s)
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