The `glcm` function outputs a `stack`, with each band containing values for each of the statistics calculated. By default, all available statistics are computed.

You won't be able to put this `stack` into a single band within the `brick` as you are trying with `band[i]<-`. This is probably what is giving you the error message. 

One solution would be to output each `stack` to a `list` and then look at stacking them together once the loop has completed.