Statistical transformation for rasters
Transforms raster to a specified statistical transformation
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)
raster.transformation(x, trans = "norm", smin = 0, smax = 255)
x |
raster 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 |
raster class object of transformation
Jeffrey S. Evans jeffrey_evans@tnc.org
library(raster)
r <- raster(nrows=100, ncols=100, xmn=571823, xmx=616763,
ymn=4423540, ymx=4453690)
r[] <- runif(ncell(r), 1000, 2500)
# Postive 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) ) )
}Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.