How can I use a custom function with FILTER? - google-apps-script

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.

Answer 2

It doesn't work because address is, if you pass only one cell as arg a string, a range, a matrix of string.
So you return a string, FILTER use a boolean array to filter data, so the condition of your filter is string < number.
You just have to convert the string to a number when you returning a value
/*
* Return the number preceding 'N' in an address
* '445 N 400 E' => '445'
* '1083 E 500 N' => '500'
*/
function NorthAddress(address) {
if(typeof address == "string"){
if (!address) return "#N/A";
else {
var North = new RegExp('([0-9]+)[\\s]+N');
var match = address.match(North);
if (match && match.length >= 2) {
return parseInt(match[1]);
}
return "#N/A";
}
} else {
var matrix = new Array();
for(var i = 0; i<address.length; i++){
matrix[i] = new Array();
for(var j = 0; j<address[i].length; j++){
var North = new RegExp('([0-9]+)[\\s]+N');
var match = address[i][j].match(North);
if (match && match.length >= 2) {
matrix[i].push(parseInt(match[1]));
}
}
}
return matrix;
}
}
Hope this will help.

Answer 3

I will add this as an answer, because I found the custom function returns an error if numerical values are passed in the referenced cell or range when toString() is not invoked:
function NorthAddress(address) {
if (!address) return null;
else {
if (address.constructor == Array) {
var result = address;
}
else {
var result = [[address]];
}
var north = new RegExp('([0-9]+)[\\s]+N');
var match;
for (var i = 0; i < result.length; i++) {
for (var j = 0; j < result[0].length; j++) {
match = result[i][j].toString().match(north);
if (match && match.length >= 2) {
result[i][j] = parseInt(match[1]);
}
else {
result[i][j] = null;
}
}
}
return result;
}
}