R: Stretch

stretch {raster} | R Documentation

## 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 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 quintile bound of original value. Ignored if smin is supplied
`maxq` | numeric <= 1 and larger than minq. upper quintile 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 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

    r <- raster(nc=10, nr=10)
    values(r) <- rep(1:2, 50)
    stretch(r)
    s <- stack(r, r*2)
    stretch(s)

[Package raster version 3.3-7 Index]