strech: Stretch

In raster: Geographic Data Analysis and Modeling

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 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

Value

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)

Example output

Loading required package: sp
class       : RasterLayer 
dimensions  : 10, 10, 100  (nrow, ncol, ncell)
resolution  : 36, 18  (x, y)
extent      : -180, 180, -90, 90  (xmin, xmax, ymin, ymax)
coord. ref. : +proj=longlat +datum=WGS84 
data source : in memory
names       : layer 
values      : 0, 255  (min, max)

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)
coord. ref. : +proj=longlat +datum=WGS84 
data source : in memory
names       : layer.1, layer.2 
min values  :       0,       0 
max values  :     255,     255 

raster documentation built on Jan. 5, 2021, 3:01 a.m.