Observer Command

nsum4 `variable1 variable2`

For each patch, takes the sum of `variable1` from the non-diagonal (N,E,S,W) neighboring patches and places it in `variable2`. `Variable` should be a patch variable. Note: `nsum4` must be run by the observer, even though it affects patches.

Examples:
`nsum4 grass totalgrass` adds up the value of `grass` in the non-diagonal patches and places it in `totalgrass`.

Related commands:
nsum diffuse