Hi Jacob,
Thanks for the suggestion. So...

func <- function(X) {x <- movingFun(c(X), n=3, sum, 'from', 
circular=TRUE);return(x)}
mon_stac <- stack(paste(pc_clim,"",y,"_prec",1:12,".asc", sep=""))
# then
wetness_quarters <- calc(mon_stac, func)
Error in .local(x, fun, ...) : function 'fun' returns more than one value

# This make sense that this would do this..
# Now this to get the first month of the max quarter by returning first 
month number:
func <- function(X) {x <- which.max(movingFun(c(X), n=3, sum, 'from', 
circular=TRUE));return(x)}

# Then
wetness_quarters <- calc(mon_stac, func)
Error in v[, tr$row[i]:(tr$row[i] + tr$nrows[i] - 1)] <- matrix(sv, nrow 
= ncol(outraster)) :
   incorrect number of subscripts on matrix
# This error being returned after a long time busying a quadcore computer...

Even if I can get your suggestion to work, I am still faced with the 
problem of retrieving the sum of values of the quarter marked my the 
month number,
which should look something like this:

quart_value <- function(a,b,d,e,f,g,i,j,k,l,m,n,o){
                     ifelse(o==1, X <- mean(c(a,b,d)),
                     ifelse(o==2, X <- mean(c(b,d,e)),
                     ifelse(o==3, X <- mean(c(d,e,f)),
                     ifelse(o==4, X <- mean(c(e,f,g)),
                     ifelse(o==5, X <- mean(c(f,g,i)),
                     ifelse(o==6, X <- mean(c(g,i,j)),
                     ifelse(o==7, X <- mean(c(i,j,k)),
                     ifelse(o==8, X <- mean(c(j,k,l)),
                     ifelse(o==9, X <- mean(c(k,l,m)),
                     ifelse(o==10, X <- mean(c(l,m,n)),
                     ifelse(o==11, X <- mean(c(m,n,a)),
                     ifelse(o==12, X <- mean(c(n,a,b)),NA))))))))))))
                     return(X)}

#For BIO8
mon_stac.wq <- stack(paste(pc_clim,"",y,"_tmean",1:12,".asc", sep=""), 
wetness_quarters)
tmean.wq <- overlay(mon_stac.wq, fun=quart_value)

With "o" being the product of the "func"or "maxmonth" function
I think that I NEED to get the "overlay" function to work, but am of 
course open to suggestions.
I appreciate the help.

Regards,
Brian


On 11/8/2010 10:59 AM, Jacob van Etten wrote:
> I don´t know what the problem is with overlay(), but you could use an 
> alternative approach, using calc() instead.
>
> Something like this (not tried)
>
> library(raster)
> library(dismo)
> func <- function(x, ...) movingFun(x, n=3, sum, circular=TRUE)
> wetness_quarters <- calc(mon_stac, func)
> wettest_quarter <- calc(wetness_quarters, function(x) which(x == max(x))
>
> The output input should indicate the month in the centre of the 
> wettest quarter.
>
> Jacob.
>
> --- On *Mon, 8/11/10, Brian Oney /<zenlines@gmail.com>/* wrote:
>
>
>     From: Brian Oney <zenlines@gmail.com>
>     Subject: [R-sig-Geo] Bioclimatic variables - wettest quarter
>     To: r-sig-geo@stat.math.ethz.ch
>     Date: Monday, 8 November, 2010, 1:40
>
>     Hello All,
>
>     I am attempting to reproduce the bioclimatic (Worldclim, Hijmans et al
>     2005) variables with the raster package and I am stuck on the group
>     "temp of driest quarter" etc. variables.
>     I am attempting it with the function "overlay" ("raster" package).
>
>     Here is how it looks:
>     # To know the first month of the wettest quarter
>     maxmonth<- function(a,b,d,e,f,g,i,j,k,l,m,n){
>                         o<- sum(c(a,b,d))
>                         p<- sum(c(b,d,e))
>                         r<- sum(c(d,e,f))
>                         u<- sum(c(e,f,g))
>                         v<- sum(c(f,g,i))
>                         w<- sum(c(g,i,j))
>                         x<- sum(c(i,j,k))
>                         y<- sum(c(j,k,l))
>                         z<- sum(c(k,l,m))
>                         aa<- sum(c(l,m,n))
>                         ab<- sum(c(m,n,a))
>                         ac<- sum(c(n,a,b))
>                         ad<- which.max(c(o,p,r,u,v,w,x,y,z,aa,ab,ac))
>                         return(ad)}
>     > 
>     maxmonth(a=13,b=16,d=41,e=61,f=41,g=16,i=15,j=14,k=13,l=11,m=31,n=11)
>     # works: 2nd element (month) is the beginning of the wettest quarter
>     [1] 2
>     mon_stac<- stack(paste(pc_clim,"",y,"_prec",1:12,".asc", sep=""))
>     # Now attempt it
>     avg<- overlay(mon_stac, fun=maxmonth)
>     Error in .overlayList(rasters, fun = fun, filename = filename, ...) :
>       cannot use this formula; lenghts do not match
>
>     # How about manually?
>     a<- raster(paste(pc_clim,"",y,"_prec",1,".asc", sep=""))
>     b<- raster(paste(pc_clim,"",y,"_prec",2,".asc", sep=""))
>     d<- raster(paste(pc_clim,"",y,"_prec",3,".asc", sep=""))
>     e<- raster(paste(pc_clim,"",y,"_prec",4,".asc", sep=""))
>     f<- raster(paste(pc_clim,"",y,"_prec",5,".asc", sep=""))
>     g<- raster(paste(pc_clim,"",y,"_prec",6,".asc", sep=""))
>     i<- raster(paste(pc_clim,"",y,"_prec",7,".asc", sep=""))
>     j<- raster(paste(pc_clim,"",y,"_prec",8,".asc", sep=""))
>     k<- raster(paste(pc_clim,"",y,"_prec",9,".asc", sep=""))
>     l<- raster(paste(pc_clim,"",y,"_prec",10,".asc", sep=""))
>     m<- raster(paste(pc_clim,"",y,"_prec",11,".asc", sep=""))
>     n<- raster(paste(pc_clim,"",y,"_prec",12,".asc", sep=""))
>
>     avg<- overlay(a,b,d,e,f,g,i,j,k,l,m,n, fun=maxmonth)
>     Error in .overlayList(rasters, fun = fun, filename = filename,
>     datatype
>     = datatype,  :
>       cannot use this formula; lenghts do not match
>
>     Also doesn't work...
>     >  length(mon_stac[1])
>     [1] 12
>     I have 12 rasters being fed into overlay, but it won't buy it.
>     I think that my first step is to know the first month of the wettest
>     month. Once I can do that I can do it for temperature as well.
>
>     Thanks and Regards,
>     Brian
>
>     _______________________________________________
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>
>

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