topic Re: I am trying to use a function with visualizationVariables in a simple renderer in ArcGIS JavaScript Maps SDK Questions

I am trying to use a function with visualizationVariables in a simple renderer

MichaelWerling — Sun, 12 Dec 2021 15:57:28 GMT

I have a function

var getMetricValue() {
   var result = // magic happens here to generate a value based on various factors
   return result;
}

and a simple renderer:

var myRenderer = new SimpleRenderer({
   symbol: new SimpleMarkerSymbol({
      size: 8,
      outline: {
         width: 0.5,
         color: 'black',
         style: 'solid'
      }
   }),
   visualVariables: [{
      type: 'color',
      field: getWellMetric,
      stops: [
      {value: 0, color: 'red'},
      {value: 100, color: 'blue'}
   ]
   }]

});

However, no matter what value I return from my function I get the same red symbol, even if I hard-code the return value to 100. The documentation states that the field for a visualVariables can be a function. If I use the same method for the field in a classBreaksRenderer then it works OK, but I want a continuous value renderer, not a breaks. Am I using this capability wrong, or is there some other issue?

Re: I am trying to use a function with visualizationVariables in a simple renderer

RobertScheitlin__GISP — Fri, 25 Aug 2017 02:37:40 GMT

Michael,

I am not seeing in the doc where it says that the field can be a function..?

Re: I am trying to use a function with visualizationVariables in a simple renderer

MichaelWerling — Fri, 25 Aug 2017 11:36:07 GMT

At Renderer | API Reference | ArcGIS API for JavaScript 4.4 (the description of ColorVisualVariable) the property field lists both String and Function as the data type.

Re: I am trying to use a function with visualizationVariables in a simple renderer

RobertScheitlin__GISP — Fri, 25 Aug 2017 11:38:48 GMT

Michael,

OK it helps if you mention you are using the 4.x API. I did not see that tag earlier.

Re: I am trying to use a function with visualizationVariables in a simple renderer

RobertScheitlin__GISP — Fri, 10 Dec 2021 21:45:43 GMT

Michael,

Here is a sample for that:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no">
  <title>Data-driven continuous color - 4.4</title>

  <link rel="stylesheet" href="https://js.arcgis.com/4.4/esri/css/main.css">
  <script src="https://js.arcgis.com/4.4/"></script>

  <style>
    html,
    body,
    #viewDiv {
      padding: 0;
      margin: 0;
      height: 100%;
      width: 100%;
    }
  </style>

  <script>
    require([
      "esri/Map",
      "esri/views/MapView",
      "esri/layers/FeatureLayer",
      "esri/renderers/SimpleRenderer",
      "esri/symbols/SimpleFillSymbol",
      "esri/widgets/Legend",
      "dojo/domReady!"
    ], function(
      Map, MapView, FeatureLayer, SimpleRenderer, SimpleFillSymbol, Legend
    ) {

      var defaultSym = new SimpleFillSymbol({
        outline: {
          color: "lightgray",
          width: 0.5
        }
      });

      // limit visualization to southeast U.S. counties
      var defExp = ["STATE = 'LA'", "STATE = 'AL'",
        "STATE = 'MS'", "STATE = 'TN'", "STATE = 'GA'",
        "STATE = 'FL'", "STATE = 'SC'", "STATE = 'NC'"
      ];

      /*****************************************************************
       * Set a color visual variable on the renderer. Color visual variables
       * create continuous ramps that map low data values to weak or
       * neutral colors and high data values to strong/deep colors. Features
       * with data values in between the min and max data values are assigned
       * a color proportionally between the min and max colors.
       *****************************************************************/

      function getMetricValue(evt) {
         var result = evt.attributes.POP_POVERTY / 2;
         return result;
      }

      var renderer = new SimpleRenderer({
        symbol: defaultSym,
        label: "% population in poverty by county",
        visualVariables: [{
          type: "color",
          field: getMetricValue,
          normalizationField: "TOTPOP_CY",
          stops: [
          {
            value: 0.1,
            color: "#FFFCD4",
            label: "<10%"
          },
          {
            value: 0.3,
            color: "#350242",
            label: ">30%"
          }]
        }]
      });

      var povLyr = new FeatureLayer({
        url: "https://services.arcgis.com/V6ZHFr6zdgNZuVG0/arcgis/rest/services/counties_politics_poverty/FeatureServer/0",
        renderer: renderer,
        outFields: ["*"],
        popupTemplate: {
          title: "{COUNTY}, {STATE}",
          content: "{POP_POVERTY} of {TOTPOP_CY} people live below the poverty line.",
          fieldInfos: [
          {
            fieldName: "POP_POVERTY",
            format: {
              digitSeparator: true,
              places: 0
            }
          }, {
            fieldName: "TOTPOP_CY",
            format: {
              digitSeparator: true,
              places: 0
            }
          }]
        },
        definitionExpression: defExp.join(" OR ") // only display counties from states in defExp
      });

      var map = new Map({
        basemap: "gray",
        layers: [povLyr]
      });

      var view = new MapView({
        container: "viewDiv",
        map: map,
        center: [-85.050200, 33.125524],
        zoom: 6
      });

      /******************************************************************
       *
       * Add layers to layerInfos on the legend
       *
       ******************************************************************/

      var legend = new Legend({
        view: view,
        layerInfos: [
        {
          layer: povLyr,
          title: "Poverty in the southeast U.S."
        }]
      });

      view.ui.add(legend, "top-right");

    });
  </script>
</head>

<body>
  <div id="viewDiv"></div>
</body>

</html>
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Re: I am trying to use a function with visualizationVariables in a simple renderer

MichaelWerling — Fri, 25 Aug 2017 14:52:02 GMT

Robert,

Thanks for the comprehensive example. I have your code working fine, so now I need to track through and find differences with my implementation. You answered the core question - a function works fine as the field.

Thanks again

Mike