# R/p9Calc.R In BioCalc: Bioclim Variables Calculator

```# Author: Julian Ramirez, [email protected]
# Date :  December 2009
# Version 0.1
# Licence GPL v3

p9Calc <- function(rlist, rlist2, outfile, format='') {

if (!is.list(rlist)) {
stop('First argument should be a list or rasters (prec)')
} else if (!is.list(rlist2)) {
stop('Second argument should be a list or rasters (tmean)')
}

if (!file.exists(outfile)) {
cat("", "\n", "Mean Temperature of Driest Quarter (P9)", "\n")

PpTaStack <- stack(c(rlist, rlist2))

p9fun <- function(DataPixel) {
if(is.na(DataPixel[1])) {
return(NA)
} else {

q1 <- -9999
mnt12 <- -9999

for (wm in 1:12) {
i <- wm
j <- wm + 1
k <- wm + 2

PptDataPixel <- DataPixel[1:12]
TavDataPixel <- DataPixel[13:24]

if (j > 12) {j <- j-12}
if (k > 12) {k <- k-12}

assign(paste("q", wm, sep=""), PptDataPixel[i] + PptDataPixel[j] + PptDataPixel[k])
assign(paste("t", wm, sep=""), TavDataPixel[i] + TavDataPixel[j] + TavDataPixel[k])
}

mnt1 <- 1
dry1 <- q1

for (wm in 1:11) {
j <- wm + 1
assign(paste("mnt", j, sep=""), if (get(paste("q", j, sep="")) < get(paste("dry", wm, sep=""))) {j} else {get(paste("mnt", wm, sep=""))})
assign(paste("dry", j, sep=""), if (get(paste("q", j, sep="")) < get(paste("dry", wm, sep=""))) {get(paste("q", j, sep=""))} else {get(paste("dry", wm, sep=""))})
}
drym <- mnt12

for (wm in 1:12) {
assign(paste("yy", wm, sep=""), if (drym == wm) {get(paste("t", wm, sep=""))} else {-9999})
}
res <- round(max(yy1,yy2,yy3,yy4,yy5,yy6,yy7,yy8,yy9,yy10,yy11,yy12) / 3)
return(res)
}
}

p9 <- raster(PpTaStack, 0)
filename(p9) <- outfile

pb <- pbCreate(nrow(PpTaStack), type='text', style=3)
for (rw in 1:nrow(PpTaStack)) {
rowVals <- getValues(PpTaStack, rw)

RasVals <- apply(rowVals, 1, p9fun)
p9 <- setValues(p9, RasVals, rw)
p9 <- writeRaster(p9, outfile, format=format, overwrite=TRUE)

pbStep(pb, rw)
}
pbClose(pb)
rm(PpTaStack)
} else {