Predominance

Census tracts styled with a unique value renderer, visual variables, and an Arcade expression to show income by predominant educational attainment

What is a predominance style?

A predominance style colors features based on the category with the highest (or predominant) number among a set of similar categories. You can use this style to map anything that involves sub-categories of a larger population.

The winner of an election
The predominant language spoken at home
The most common race/ethnicity in a region

How a predominance style works

This style requires writing an Arcade expression that returns the category with the largest number. The following expression returns a string for the predominant educational attainment level for a given feature.

Expand
Use dark colors for code blocksCopy
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
      // store field values in variables with
      // meaningful names. Each is the total count
      // of people that attained each education level

      var noHighSchool = $feature.NOHS_CY;
      var someHighSchool = $feature.SOMEHS_CY;
      var highSchool = $feature.HSGRAD_CY;
      var ged = $feature.GED_CY;
      var someCollege = $feature.SMCOLL_CY;
      var associates = $feature.ASSCDEG_CY;
      var bachelors = $feature.BACHDEG_CY;
      var grad = $feature.GRADDEG_CY;

      var all = [
        noHighSchool, someHighSchool, highSchool,
        ged, someCollege, associates,
        bachelors, grad,
      ];

      // Match the maximum value with the label
      // of the respective field and return it for
      // use in a UniqueValueRenderer

      return Decode( Max(all),
        noHighSchool, 'No high school',
        someHighSchool, 'Some high school',
        highSchool, 'High school diploma',
        ged, 'GED',
        someCollege, 'Some college',
        associates, 'Associate\'s degree',
        bachelors, 'Bachelor\'s degree',
        grad, 'Master\'s degree or higher',
      'n/a' );
Expand

Once the expression is authored, create a unique value renderer and set the following:

Reference the Arcade expression in the valueExpression property.
Create unique value info objects for each of the expected values returned from the expression.

Examples

Predominant value

The following example colors each census tract based on the predominant educational attainment of adults age 25 years or older.

ArcGIS JS API
Expand
Use dark colors for code blocksCopy
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
        const colors = [ "#00b6f1", "#d9bf0d", "#6a28c7", "#c44245", "#b9a087", "#ab579d", "#78aea0", "#1e8553" ];
        const predominanceArcade = document.getElementById("predominance").text;
        const renderer = {
          type: "unique-value",
          valueExpression: predominanceArcade,
          valueExpressionTitle: "Predominant educational attainment",
          uniqueValueInfos: [
            {
              value: "Master's degree or higher",
              symbol: createSymbol(colors[0])
            }, {
              value: "Bachelor's degree",
              symbol: createSymbol(colors[1])
            }, {
              value: "Associate's degree",
              symbol: createSymbol(colors[2])
            }, {
              value: "Some college",
              symbol: createSymbol(colors[3])
            }, {
              value: "GED",
              symbol: createSymbol(colors[4])
            }, {
              value: "High school diploma",
              symbol: createSymbol(colors[5])
            }, {
              value: "Some high school",
              symbol: createSymbol(colors[6])
            }, {
              value: "No high school",
              symbol: createSymbol(colors[7])
            }
          ]
        };
Expand

Predominance with opacity

In a predominance visualization, the color representing the predominant value will shade the whole polygon with the same opacity and saturation as any neighboring polygon even if the predominant value wins over other values by the slimmest margin.

Adding an opacity variable helps emphasize strong predominant values and wash out features where the predominant value is relatively weak. The Arcade expression can return the margin between the predominant value and the second place value, or it can be simpler and return the share of the predominant value as a percentage of all values.

ArcGIS JS API
Expand
Use dark colors for code blocksCopy
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
148
        renderer.visualVariables = [{
          type: "opacity",
          valueExpression: `
            var all = [
              $feature.NOHS_CY, $feature.SOMEHS_CY, $feature.HSGRAD_CY,
              $feature.GED_CY, $feature.SMCOLL_CY, $feature.ASSCDEG_CY,
              $feature.BACHDEG_CY, $feature.GRADDEG_CY
            ];
            var predominantValue = Max(all);
            var total = Sum(all);

            return (predominantValue / total) * 100;
          `,
          valueExpressionTitle: "% of people comprising the dominant educational attainment group",
          stops: [
            { value: 22, opacity: 0.05, label: "< 22%" },
            { value: 40, opacity: 1.0, label: "> 40%" }
          ]
        }];
Expand

Predominance with size

Many times in demographic maps, large features represent areas with fewer people. In a predominance visualization, the colors of these large features can dominate the view, thus making them appear more influential or important than they actually are.

Adding a size variable that returns the sum of all categories considered in the predominance expression can help provide additional context to the user. This requires switching from a fill symbol to a marker symbol.

This is particularly important for election maps where relatively unimportant large areas dominate the view more than high population areas.

ArcGIS JS API
Expand
Use dark colors for code blocksCopy
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
149
        renderer.visualVariables = [{
          type: "size",
          valueExpression: `
            var all = [
              $feature.NOHS_CY, $feature.SOMEHS_CY, $feature.HSGRAD_CY,
              $feature.GED_CY, $feature.SMCOLL_CY, $feature.ASSCDEG_CY,
              $feature.BACHDEG_CY, $feature.GRADDEG_CY
            ];
            var total = Sum(all);
            return total;
          `,
          valueExpressionTitle: "Population 25+",
          minSize: "2px",
          maxSize: "48px",
          minDataValue: 1000,
          maxDataValue: 15000
        }];
Expand