[R-sig-Geo] Bioclimatic variables - wettest quarter

[Brian Oney]

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