problem when doing algebra with raster layers in R

Question

I'm trying to combine bioclim raster layers to create the following layer.

(Q) = AnnPrec/[(Tmax+Tmin)*(Tmax-Tmin)]*1000

For that, I import a bioclim stack:

 envirc = stack("C:/Users/Agus/Dropbox/wiens SL paper/clime.grd")

you can get the stack here: https://www.dropbox.com/sh/n8qfu9cmuowondp/AADcFHTnCqhhoYA43UeckVS-a?dl=0

separate specific layers

 AnnPrec=subset( envirc,"bio12") 
 Tmax=subset( envirc,"bio5") 
 Tmin=subset( envirc,"bio6") 

I could use overlay function , but this seems to work

 den=((Tmax+Tmin)*(Tmax-Tmin))*1000

but now, this operation leads me to a constant value, which is incorrect, it # should be a range of values

 Q=(AnnPrec/den)

using overlay function gives me the same value

 Q=overlay(AnnPrec,Tmax,Tmin, fun=function(x,y,z){return(x/((y+z)*(y-z))*1000)})

What I'm doing wrong?

Answer 1

Hm, I don't really see the problem. overlay works just fine on my machine. Here's the code.

# (Q)=AnnPrec/[(Tmax+Tmin)*(Tmax-Tmin)]*1000
Q <- overlay(AnnPrec, Tmax, Tmin, fun = function(x, y, z) {
  x / ((y + z) * (y - z)) * 1000
}, filename = "q", overwrite = TRUE)

And here's the resulting image including the range of values.

range(Q[], na.rm = TRUE)
[1] -11629.63  12039.74

spplot(Q, at = seq(-500, 500, 10), 
       colorkey = list(space = "top", width = .6), 
       scales = list(draw = TRUE))

If that doesn't work, maybe you can provide the actual contents of AnnPrec, Tmax and Tmin as suggested by @Spacedman.