U.S. counties styled with a UniqueValueRenderer showing the predominant political party affiliation of registered voters.
What is Arcade?Sometimes you need to render an attribute that doesn't exist in your layer. Arcade is an expression language that allows you to calculate values for each feature in a layer at runtime and use those values as the basis for a data-driven visualization. This is convenient when you need to derive new data values on data sources that update frequently, or on layers that you don't own.
See the Arcade - expression language guide for more details about how to use Arcade in other parts of the ArcGIS Maps SDK for JavaScript.
How Arcade worksArcade expressions are referenced as strings in the valueExpression property of ClassBreaksRenderer, UniqueValueRenderer, DotDensityRenderer or any visual variable: color, size, opacity, and rotation. When defined, it is always used instead of referencing a field/normalizationField.
When used in a ClassBreaksRenderer, DotDensityRenderer, or any of the visual variables, the value expression must evaluate to a number. Expressions may evaluate to either strings or numbers in UniqueValueRenderer.
Examples Predominance with UniqueValueRendererIn this example, Arcade is used to create a predominance map showing the most common political party affiliation in each U.S. county. The underlying layer has three fields that identify the number of republicans, democrats, and independent/non-party voters in each county. Since the service does not contain a field indicating the predominant party, we can write an Arcade expression to identify that for each feature.
The Arcade expression is referenced in the valueExpression property of a UniqueValueRenderer.
Predominance Arcade expression
Expand
Use dark colors for code blocks Copy32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54 54
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
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
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
const renderer = {
type: "unique-value",
valueExpression: `
// store field values in variables with
// meaningful names. Each is the total count
// of votes for the respective party
var republican = $feature.MP06025a_B;
var democrat = $feature.MP06024a_B;
var independent = $feature.MP06026a_B;
var parties = [republican, democrat, independent];
// Match the maximum value with the label
// of the respective field and return it for
// use in a UniqueValueRenderer
return Decode( Max(parties),
republican, 'republican',
democrat, 'democrat',
independent, 'independent',
'n/a' );
`,
Then assign unique symbols for each expected return value in the renderer.
Unique value infos
Expand
Use dark colors for code blocks Copy57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74 74
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
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
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
uniqueValueInfos: [
{
value: "democrat",
symbol: createSymbol("#00c3ff"),
label: "Democrat",
},
{
value: "republican",
symbol: createSymbol("#ff002e"),
label: "Republican",
},
{
value: "independent",
symbol: createSymbol("#faff00"),
label: "Independent/other party",
},
],
Arcade can be used anywhere a data value is referenced in a renderer, including visual variables. The following snippet references an Arcade expression in an opacity visual variable to calculate the percentage of voters comprising the predominant party in each county. The opacity stops map the expected data values to opacity values.
Opaque counties indicate areas where the predominant political party comprises the vast majority of voters. Transparent counties show areas where there is a more diverse mix of individuals belonging to each political party.
ArcGIS JS API
Expand
Use dark colors for code blocks Copy78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
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
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
renderer.visualVariables = [
{
type: "opacity",
valueExpression: `
var republican = $feature.MP06025a_B;
var democrat = $feature.MP06024a_B;
var independent = $feature.MP06026a_B;
var parties = [republican, democrat, independent];
var total = Sum(parties);
var max = Max(parties);
return (max / total) * 100;
`,
valueExpressionTitle: "Share of registered voters comprising the dominant party",
stops: [
{ value: 33, opacity: 0.05, label: "< 33%" },
{ value: 44, opacity: 1.0, label: "> 44%" },
],
},
];
See the Arcade - expression language guide for more details about how to use Arcade in other parts of the ArcGIS Maps SDK for JavaScript.
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4