Getting field name from Arcade expression

Question

I would like to create an expression using Arcade for symbology purposes.

I have one layer with six fields, each listing a distance that the feature is from that type of infrastructure. For example, one polygon's six fields tell me it's 100 feet to the nearest railroad, 150 feet to the nearest primary road, 175 feet to the nearest secondary road, 200 feet to the nearest local road, 225 feet to the nearest other type of road, and 250 feet to the nearest trail. I would like to identify the closest infrastructure type to a feature.

I have no problem getting the nearest value; I just use the Min() function. However, I can't get the field name that the value comes from. I'd like to be able to symbolize the features with 6 different colors depending on what infrastructure type is the nearest.

Any assistance is appreciated.

kenbuja · Accepted Answer

Here's one way to do it. The variable fieldList (and Expects) contains the names of the fields you are comparing .

Expects($feature, 'railroad', 'primary_road', 'secondary_road', 'local_road', 'other_road', 'trail') //field names
var fieldList = ['railroad', 'primary_road', 'secondary_road', 'local_road', 'other_road', 'trail']
var minimum = 99999999;
var minField;
for (var i in fieldList) {
  if ($feature[fieldList[i]] < minimum) {
    minimum = $feature[fieldList[i]]
    minField = fieldList[i]
  }
}
return minField

kenbuja · Accepted Answer

But the Min function will return a 0 if one of the features has a null value. You'd have to do this to ignore either null or 0 values.

**Updated to put the IsEmpty and zero checks at the front of the if statement

Expects($feature, 'railroad', 'primary_road', 'secondary_road', 'local_road', 'other_road', 'trail') //field names
var fieldList = ['railroad', 'primary_road', 'secondary_road', 'local_road', 'other_road', 'trail']
var minimum = 99999999;
var minField;
for (var i in fieldList) {
  if (!IsEmpty($feature[fieldList[i]]) && $feature[fieldList[i]] != 0 && $feature[fieldList[i]] < minimum) {
    minimum = $feature[fieldList[i]]
    minField = fieldList[i]
  }
}
return minField