Function types identity, step

docs/utils.md

@@ -243,3 +243,24 @@ from mapboxgl.utils import create_numeric_stops, height_map
 height_stops = create_numeric_stops([0, 50, 100, 500, 1500], 0, 150000)
 height = height_map(117, height_stops)
 ```
+
+## step_map
+Return a color or numeric value with a 'step'-type expression from given color_stops or numeric_stops; for use with 'step' expression type (color_function_type, radius_function_type, height_function_type).
+
+### Params
+**step_map**(_lookup, step_stops, default='rgb(122,122,122)'_)
+
+Parameter | Description
+--|--
+lookup | value maybe be numeric for interpolated values or string for categorical stops
+step_stops | height ramp stops generated from `create_numeric_stops`, or custom list of numeric or categorical stops with paired heights
+default | default value (color or numeric) used for values below the minimum color or numeric break
+
+### Usage
+```python
+from mapboxgl.utils import create_color_stops, step_map
+
+# assign color with a step function
+color_stops = create_color_stops([0, 50, 100, 500, 1500], colors='YlOrRd')
+color = step_map(73, color_stops, 'white')
+```

docs/viz.md

@@ -102,6 +102,19 @@ Generate stops array for use with match expression in mapbox template.
 Determines if features are defined as vector source based on MapViz arguments.
 
 
+## class ExpressionsMixin
+
+The `ExpressionsMixin` class is a parent class of the various `mapboxgl-jupyter` visualizations supporting validations of the combinations of viz settings and selected expression types before rendering the map. `CircleViz`, `GraduatedCircleViz`, `HeatmapViz`, `ChoroplethViz`, and `LinestringViz` inherit from this mixin class.
+
+### Methods
+**validate_function_types**(_self_)
+Raise an error if color_function_type, radius_function_type, or height_function_type do not match the allowed values (one of `interpolate`, `match`, `identity`, or `step`.)
+
+**validate_legend_settings**(_self_)
+Warning if the property function_type for the legend property is `identity` and `self.legend = True`.  Legend will not display with `identity`.
+Also raises an error if `legend_gradient` is True and color_function_type is one of `identity` or `step`.
+
+
 ## class CircleViz
 
 The `CircleViz` class handles the creation of a circle map and is built on top of the `MapViz` class.
@@ -114,8 +127,8 @@ Parameter | Description
 data | name of GeoJson file or object or JSON join-data
 color_property | property to determine circle color
 color_stops | property to determine circle color
-color_default | color of circle to use if no lookup value matches the property value. Only used for the **match** color_function_type.
-color_function_type | property to determine `type` used by Mapbox to assign color. One of 'interpolate' or 'match'. Default is interpolate
+color_default | color of circle to use if no lookup value matches the property value. Only used for the **match** or **step** color_function_type.
+color_function_type | property to determine `type` used by Mapbox to assign color. One of 'interpolate', 'match', 'identity' or 'step'. Default is interpolate
 stroke_color | color of circle outline stroke
 stroke_width | width (in pixels) of circle outline stroke
 
@@ -233,12 +246,12 @@ Parameter | Description
 data | name of GeoJson file or object or JSON join-data
 color_property | property to determine circle color.
 color_stops | property to determine circle color.
-color_default | color of the circle to use if no lookup value matches the property value. Only used for the **match** color_function_type.
-color_function_type | property to determine `type` used by Mapbox to assign color. One of "interpolate" or "match". Default is interpolate.
+color_default | color of the circle to use if no lookup value matches the property value. Only used for the **match** or **step** color_function_type.
+color_function_type | property to determine `type` used by Mapbox to assign color. One of "interpolate", "match", "identity" or "step". Default is interpolate.
 radius_property | property to determine circle radius.
 radius_stops | property to determine circle radius.
-radius_default | radius of the circle to use if no lookup value matches the property value. Only used for the **match** radius_function_type.
-radius_function_type | property to determine `type` used by Mapbox to assign radius size. One of "interpolate" or "match". Default is interpolate.
+radius_default | radius of the circle to use if no lookup value matches the property value. Only used for the **match** or **step** radius_function_type.
+radius_function_type | property to determine `type` used by Mapbox to assign radius size. One of "interpolate", "match", "identity" or "step". Default is interpolate.
 stroke_color | Color of stroke outline on circles
 stroke_width | Width of stroke outline on circles
 
@@ -368,7 +381,7 @@ data | can be either GeoJSON (containing polygon features) or JSON for data-join
 label_property | property to use for marker label | 'density'
 color_property | property to determine fill color | 'density'
 color_stops | property to determine fill color | [[0, 'red'], [0.5, 'blue'], [1, 'green']]
-color_default | property to determine default fill color in match lookups | '#F0F0F0'
+color_default | property to determine default fill color in match lookups and step lookups | '#F0F0F0'
 color_function_type | property to determine type of expression used by Mapbox to assign color | 'interpolate'
 line_color | property to determine choropleth border line color | '#FFFFFF'
 line_stroke | property to determine choropleth border line stroke (one of solid (-), dashed (--), dotted (:), dash dot (-.)) | 'solid' or '-'

examples/data/state_colors.geojson

@@ -0,0 +1,97 @@
+{ 
+  "type": "FeatureCollection", 
+  "features": [
+    {
+      "type": "Feature", 
+      "id": "49", 
+      "properties": {
+        "name": "Utah", 
+        "density": 34.3,
+        "color": "gold",
+        "height": 100000
+      }, 
+      "geometry": {
+        "type": "Polygon", 
+        "coordinates": [
+                        [
+                          [-112.164359, 41.995232], 
+                          [-111.047063, 42.000709], 
+                          [-111.047063, 40.998429], 
+                          [-109.04798, 40.998429], 
+                          [-109.053457, 39.125316], 
+                          [-109.058934, 38.27639], 
+                          [-109.042503, 38.166851], 
+                          [-109.042503, 37.000263], 
+                          [-110.499369, 37.00574], 
+                          [-114.048427, 37.000263], 
+                          [-114.04295, 41.995232], 
+                          [-112.164359, 41.995232]
+                        ]
+                      ]
+      }
+    },
+    {
+      "type": "Feature", 
+      "id": "08", 
+      "properties": {
+        "name": "Colorado", 
+        "density": 49.33,
+        "color": "skyblue",
+        "height": 300000
+      }, 
+      "geometry": {
+        "type": "Polygon", 
+        "coordinates": [
+                        [
+                          [-107.919731, 41.003906], 
+                          [-105.728954, 40.998429], 
+                          [-104.053011, 41.003906], 
+                          [-102.053927, 41.003906], 
+                          [-102.053927, 40.001626], 
+                          [-102.042974, 36.994786], 
+                          [-103.001438, 37.000263], 
+                          [-104.337812, 36.994786], 
+                          [-106.868158, 36.994786], 
+                          [-107.421329, 37.000263], 
+                          [-109.042503, 37.000263], 
+                          [-109.042503, 38.166851], 
+                          [-109.058934, 38.27639], 
+                          [-109.053457, 39.125316], 
+                          [-109.04798, 40.998429], 
+                          [-107.919731, 41.003906]
+                        ]
+                      ]
+      }
+    }, 
+    {
+      "type": "Feature", 
+      "id": "56", 
+      "properties": {
+        "name": "Wyoming", 
+        "density": 5.851,
+        "color": "orange",
+        "height": 200000
+      }, 
+      "geometry": {
+        "type": "Polygon", 
+        "coordinates": [
+                        [
+                          [-109.080842, 45.002073], 
+                          [-105.91517, 45.002073], 
+                          [-104.058488, 44.996596], 
+                          [-104.053011, 43.002989], 
+                          [-104.053011, 41.003906], 
+                          [-105.728954, 40.998429], 
+                          [-107.919731, 41.003906], 
+                          [-109.04798, 40.998429], 
+                          [-111.047063, 40.998429], 
+                          [-111.047063, 42.000709], 
+                          [-111.047063, 44.476286], 
+                          [-111.05254, 45.002073], 
+                          [-109.080842, 45.002073]
+                        ]
+                      ]
+      }
+    }
+  ]
+}