I'm using version 5.5 and I've written a program to calculate various landscape metrics from a random array. I'm getting good results when the size of the random array is (50,50), (100,100), (500,500), but when I make the array (1277,1654) which is the size I need, I get odd results. Below is part of the code and the problematic results, the rest of the code seems to be working fine. patches = max(regions) patch_sizes = 0 for i = 0, patches-1 do begin t = i + 1 size = (regions eq t) eachsize = total(size) lastsize = patch_sizes if eachsize gt lastsize then begin patch_sizes = eachsize endif else begin patch_sizes = lastsize endelse endfor largest_patch(iter) = patch_sizes and the result: the largest patch of each array = 7 10 26 37 0 0 0 0 894100 1036914 1152105 1261889 1368484 1473961 1579865 1685309 1790211 1895223 2001360 2106300 It's weird... all of the numbers are correct except the zeros in 5-9. These zeros are not there when the original array is smaller, they have only showed up when my array is (1277,1654). Any help would be appreciated. Thanks, Paul