How can I use a custom function with FILTER?

Question

I have a custom function defined that extracts part of an address from a string:

/*
 * Return the number preceding 'N' in an address
 *    '445 N 400 E' => '445'
 *    '1083 E 500 N' => '500'
 */
function NorthAddress(address) {
  if (!address) return null;
  else {
    var North = new RegExp('([0-9]+)[\\s]+N');
    var match = address.match(North);
    if (match && match.length >= 2) {
      return match[1];
    }
    return null;
  }
}

I want to use this function as one of the conditions in a call to FILTER(...) in the spreadsheet where I have these addresses stored:

=FILTER('Sheet 1'!A:A, NorthAddress('Sheet 1'!B:B) >= 450))

But when I call NorthAddress like this, it gets an array of all the values in column B and I can't for the life of me find any documentation as to how I need to handle that. The most obvious way (to me) doesn't seem to work: iterate over the array calling NorthAddress on each value, and return an array of the results.

What does my function need to return for FILTER to work as expected?

Answer 1

When a custom function is called passing a multi-cell range, it receives a matrix of values (2d array), it's doesn't matter if the range is a single column or a single row, it's always a matrix. And you should return a matrix as well.

Anyway, I would not use a custom function to this, as there is already the native spreadsheet formulas: RegexMatch, RegexExtract and RegexReplace formulas. To get the "if match" behavior, just wrap them in a IfError formula.