| raster.transformation {spatialEco} | R Documentation |
Statistical transformation for rasters
Description
Transforms raster to a specified statistical transformation
Usage
raster.transformation(x, trans = "norm", smin = 0, smax = 255)
Arguments
x |
A terra SpatRaster class object |
trans |
Transformation method: "norm", "rstd", "std", "stretch", "nl", "slog", "sr" (please see notes) |
smin |
Minimum value for stretch |
smax |
Maximum value for stretch |
Details
Transformation option details:
norm - (Normalization_ (0-1): if min(x) < 0 ( x - min(x) ) / ( max(x) - min(x) )
rstd - (Row standardize) (0-1): if min(x) >= 0 x / max(x) This normalizes data
-
with negative distributions
std - (Standardize) (x - mean(x)) / sdv(x)
stretch - (Stretch) ((x - min(x)) * max.stretch / (max(x) - min(x)) + min.stretch) This will stretch values to the specified minimum and maximum values (eg., 0-255 for 8-bit)
nl - (Natural logarithms) if min(x) > 0 log(x)
slog - (Signed log 10) (for skewed data): if min(x) >= 0 ifelse(abs(x) <= 1, 0, sign(x)*log10(abs(x)))
sr - (Square-root) if min(x) >= 0 sqrt(x)
Value
A terra SpatRaster class object of specified transformation
Author(s)
Jeffrey S. Evans jeffrey_evans@tnc.org
Examples
library(terra)
r <- rast(nrows=500, ncols=500, xmin=571823, xmax=616763,
ymin=4423540, ymax=4453690)
crs(r) <- "epsg:9001"
r[] <- runif(ncell(r), 1000, 2500)
# Positive values so, can apply any transformation
for( i in c("norm", "rstd", "std", "stretch", "nl", "slog", "sr")) {
print( raster.transformation(r, trans = i) )
}
# Negative values so, can't transform using "nl", "slog" or "sr"
r[] <- runif(ncell(r), -1, 1)
for( i in c("norm", "rstd", "std", "stretch", "nl", "slog", "sr")) {
try( print( raster.transformation(r, trans = i) ) )
}