Bivariate colors symbology shows the quantitative relationship between two variables in a feature layer. This type of symbology uses bivariate color schemes to visually compare, emphasize, or delineate values. Similar to graduated colors symbology, each variable is classified and each class is assigned a color. In the example below, the bivariate color scheme is the product of two variables with three discrete classes each. This creates a square grid of nine unique colors. Maps that use this type of symbology are often called bivariate choropleth maps.
Bivariate colors symbology is best used to emphasize the highest and lowest values in a dataset or to find correlations within a dataset. For example, a community organization may create a bivariate choropleth map with bivariate colors symbology to determine if there is a relationship between median household income and population growth in their city. Bivariate colors symbology can be based on attribute fields in the dataset, or you can write a custom Arcade expression to generate numeric values on which to symbolize.
Bivariate colors symbology is similar to the Relationship style in ArcGIS Online.
Draw a layer with bivariate colors symbology
To draw a feature layer with bivariate colors symbology, follow these steps:
- Choose a feature layer in the Contents pane.
- Under Feature Layer, on the Appearance tab, in the Drawing group, click Symbology and click Bivariate Colors .
The Symbology pane appears. If the layer does not have at least two numeric fields with classifiable values, a warning message appears.
- In the Symbology pane, on the Primary symbology tab , click the Field 1 and Field 2 drop-down menus and choose the numeric fields that you want to visualize. Optionally, click the expression button to open the Expression Builder dialog box. Write an expression and click Verify to validate it. Note that although an expression is valid, it may not return a valid numeric value. You can use the filter button on the Expression Builder dialog box to show only numeric fields to help prevent this.
- Optionally, to normalize the data, choose a field from the Normalization 1 or Normalization 2 drop-down menu. You can normalize one field at a time or both fields simultaneously. Normalization is available only when the symbology is based on a field. If it is symbolized on an expression, the Normalization field is unavailable.
- Classify the data using an appropriate classification method and number of classes. Click the Method drop-down menu and choose a classification method. Defined interval and standard deviation classification are unavailable for bivariate colors symbology.
- Click the Grid Size drop-down menu and choose the number of discrete classes for both fields. You can choose from a 2x2, 3x3, or 4x4 grid.
- Click the Color scheme drop-down menu and choose a bivariate color scheme. The grid size determines which color schemes from the ArcGIS Colors system style appear in the menu. For example, if your chosen grid size is 3x3, only bivariate color schemes with three classes per variable (nine colors) are shown. Bivariate color schemes stored in your Favorites style or custom styles must match the grid size to be used to symbolize the layer.
If you are symbolizing polygons, click the Color scheme options button and choose the target for the color scheme. You can apply the colors to the polygon fills, outlines, or both. To update all symbol layers to match the color scheme target setting, click the More drop-down menu and click Regenerate all symbols.
- Optionally, click the Template symbol to open the Format Symbol pane and modify the symbol or choose a different symbol.
Modify bivariate colors symbology
Because bivariate colors symbology is conceptually a combination of two individual color schemes, the correct use of classification and color is ideal. ArcGIS Pro includes several bivariate color schemes in the ArcGIS Colors style, but you can also create custom symbols and color schemes to further visualize your layer. To learn more about bivariate color schemes, see Color schemes.
In the Symbology pane, the Primary symbology tab has three subtabs where bivariate color symbology can be modified:
- The Field 1 Histogram and Field 2 Histogram tabs show the data ranges of the symbol classes. Histograms offer a visual tool for understanding how the data is represented by the chosen classification method.
- The gray bars of the histograms represent the distribution of the data. The value stops show how the classification method applies to the data distribution.
- You can drag the class breaks up or down manually or change the Method to automatically set the class break positions.
- To view the distribution and class breaks more easily, you can drag the expander bar above the histogram upward to make it larger in the pane.
- To reset each symbol class to its default symbol based on current symbology parameters, click the More drop-down menu and click Regenerate all symbols. You may want to do this after setting the color scheme target or to reset the symbology after making a lot of individual symbol edits.
- The Legend tab shows the details of the layer's legend as symbolized by bivariate colors. Click this tab to view and format the labels and orientation of the legend as it appears in the Contents pane and in layouts.
- Expand Fields. The two color schemes represent the part of the color scheme applied to the listed field. The field aliases are also displayed and can be customized.
- Expand Orientation to change the overall shape and focus of the legend. The legend is a square by default, but it can be rotated 45 degrees to highlight the highest or lowest values of either field.
- Expand Labels to make modifications to the legend labels. To change where labels appear in the legend, click Label sides or Label corners. Each text box shows the location of the label with an icon, which depends on the orientation of the legend.
In the Symbology pane, click the Advanced symbology options tab to set the sample size for your data and use feature level masking.
Vary bivariate color symbology by transparency, rotation, or size
In addition to comparing quantitative values with bivariate colors symbology, you can also symbolize additional attributes by varying the outline width or transparency of the bivariate color symbols. While all of these treatments can be applied simultaneously, compounded visual variation can make the symbology difficult to interpret. Use and apply secondary symbology sparingly.
- In the Symbology pane, click the Vary symbology by attribute tab .
- Expand Transparency, Rotation, or Size. With polygon features, Outline width replaces Size and Rotation is not available.