https://github.com/cran/fields
Tip revision: 6c8b30169bba182a68765ee3cb9b4e2ef7d38332 authored by Doug Nychka on 16 November 2011, 00:00:00 UTC
version 6.6.3
version 6.6.3
Tip revision: 6c8b301
D4transform.image.R
# fields, Tools for spatial data
# Copyright 2004-2011, Institute for Mathematics Applied Geosciences
# University Corporation for Atmospheric Research
# Licensed under the GPL -- www.gpl.org/licenses/gpl.html
"D4transform.image" <- function(x, inv = FALSE, transpose = FALSE,
cut.min = 8) {
if (transpose)
inv <- !inv
n <- dim(x)[1]
m <- dim(x)[2]
if (n > m) {
flip <- TRUE
temp <- t(x)
n <- dim(temp)[1]
m <- dim(temp)[2]
}
else {
flip <- FALSE
temp <- x
}
if (n > m)
stop(" number of columns of x must >= to number of\nrows")
nn <- n
mm <- m
if (!inv) {
while (nn > cut.min) {
temp[1:nn, 1:mm] <- WD42d(temp[1:nn, 1:mm])
nn <- nn/2
mm <- mm/2
}
}
if (inv) {
NN <- n
MM <- m
while (NN > cut.min) {
NN <- NN/2
MM <- MM/2
}
nn <- NN * 2
mm <- MM * 2
while (nn <= n) {
temp[1:nn, 1:mm] <- WD42di(temp[1:nn, 1:mm])
nn <- nn * 2
mm <- mm * 2
}
}
if (flip) {
return(t(temp))
}
else {
return(temp)
}
}