strech.RdLinear 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 class 'Raster'
stretch(x, minv=0, maxv=255, minq=0, maxq=1, smin=NA, smax=NA,
samplesize=1000000, filename='', ...)Raster object
numeric >= 0 and smaller than maxv. lower bound of stretched value
numeric <= 255 and larger than maxv. upper bound of stretched value
numeric >= 0 and smaller than maxq. lower quantile bound of original value. Ignored if smin is supplied
numeric <= 1 and larger than minq. upper quantile bound of original value. Ignored if smax is supplied
numeric < smax. user supplied lower value for the layers, to be used instead of a quantile computed by the function itself
numeric > smin. user supplied upper value for the layers, to be used instead of a quantile computed by the function itself
numeric > 1. If samplesize < ncell(x), a regular sample of samplesize is taken from x to compute the quantiles (to speed things up)
character. Filename for the output Raster object (optional)
additional arguments as for writeRaster
Raster
stretch argument in plotRGB
r <- raster(nc=10, nr=10)
values(r) <- rep(1:2, 50)
stretch(r)
#> class : RasterLayer
#> dimensions : 10, 10, 100 (nrow, ncol, ncell)
#> resolution : 36, 18 (x, y)
#> extent : -180, 180, -90, 90 (xmin, xmax, ymin, ymax)
#> crs : +proj=longlat +datum=WGS84 +no_defs
#> source : memory
#> names : layer
#> values : 0, 255 (min, max)
#>
s <- stack(r, r*2)
stretch(s)
#> class : RasterBrick
#> dimensions : 10, 10, 100, 2 (nrow, ncol, ncell, nlayers)
#> resolution : 36, 18 (x, y)
#> extent : -180, 180, -90, 90 (xmin, xmax, ymin, ymax)
#> crs : +proj=longlat +datum=WGS84 +no_defs
#> source : memory
#> names : layer.1, layer.2
#> min values : 0, 0
#> max values : 255, 255
#>