Scale (gain) and offset — scoff • terra

These functions can be used to get or set the scale (gain) and offset parameters used to transform values when reading raster data from a file. The parameters are applied to the raw values using the formula below:

value <- value * scale + offset

The default value for scale is 1 and for offset is 0. 'scale' is sometimes referred to as 'gain'.

Note that setting the scale and/or offset are intended to be used with values that are stored in a file. When values are memory, assigning scale or offset values will lead to the immediate computation of new values; in such cases it would be clearer to use Arith-methods.

Usage

# S4 method for class 'SpatRaster'
scoff(x)

# S4 method for class 'SpatRaster'
scoff(x) <- value

Arguments

x: SpatRaster
value: two-column matrix with scale (first column) and offset (second column) for each layer. Or NULL to remove all scale and offset values

Value

matrix or changed SpatRaster

Examples

r <- rast(system.file("ex/elev.tif", package="terra"))
minmax(r)
#>     elevation
#> min       141
#> max       547
scoff(r)
#>      scale offset
#> [1,]     1      0
r[4603]
#>   elevation
#> 1       279

scoff(r) <- cbind(10, 5)
minmax(r)
#>     elevation
#> min      1415
#> max      5475
scoff(r)
#>      scale offset
#> [1,]    10      5
r[4603]
#>   elevation
#> 1      2795