I have a feature layer of polygons in my map (I'm using version 3.16). I have fields in this layer that I want to use to label the polygons. I have been able to use LabelClass and labelExpressionInfo to simply label the polygons with values from individual fields. Now I want to take it a step further. Is it possible to use a function to label my polygons with the result of subtracting one field’s values from another?
For example, I have two fields named JanTemp and JanNormTemp. One polygon has a JanTemp value of 27.9 and a JanNormTemp of 29.4. I’m trying to symbolize and label the polygons with the departure from Norm value, which in this case would be -1.5. I don’t want to just add a new field to the polygons and calculate the departures… I’m trying to have this figure itself out programmatically.
I was able to get the ClassBreaksRenderer to do this. Here is the function I defined first:
// Function for renderer
rendfunc = function(value) {
var attr = value.attributes;
var start = attr[field1];
var minus = attr[field2];
return (start-minus);
}And then here is the line I used to create the CBR:
// Set up renderer
var flyrRenderer = new CBRenderer(null, rendfunc);
So far I have unsuccessful with my attempts at labeling the polygons in a similar fashion. Has anyone else done this?
