I am trying to write a function

[offset,coffset]=findLowNhbr(map) 

that for each pixel in a map finds the eight neighbors to the pixel, and returns two matrices with both the row and column offsets to the lowest neighbor (uses the numbers -1, 0 and 1). Border pixels are given 0 offsets for both the row and column, since they do not have neighbors.

Here is what I think the general plan for this function should be:

1. For each point, find the eight nearest neighbors.
2. If the neighbor is lower than the point, return -1
3. If the neighbor is at the same elevation as the point, return 0
4. If the neighbor is higher than the point, return +1
5. Store these offsets in two matrices.

I am at a complete loss as to where to start, so any advice or questions are welcome!