Using graduated symbols
The graduated symbol renderer is one of the common renderer types used to represent quantitative information. Using a graduated symbols renderer, the quantitative values for a field are grouped into ordered classes. Within a class, all features are drawn with the same symbol. Each class is assigned a graduated symbol from smallest to largest.
A key design aspect in using graduated symbols for a layer is about classifying numerical data. See Classifying numerical fields for graduated symbology for a good overview on the classification methods available in ArcGIS.
- Right-click the layer in the table of contents and click Properties.
- Click the Symbology tab on the Layer Properties dialog box.
Click Quantities and click Graduated symbols.
- Select the numeric field that contains the quantitative data you want to map.
Optionally, select a Normalization field to normalize the data. The values in this field will be used to divide the Value field to create ratios.
- Enter the minimum and maximum symbol sizes and click the Classify button.
- Select the classification method you want to use and enter the number of classes you want to display. See Classifying numerical fields for graduated symbology for more information.
- Click OK.
Normalization ratios are useful when other factors influence the numerical values you are classifying and displaying. For example, population can be influenced by each county's size. You can divide population by area (in this case, acres).
- You can set format properties for the class range labels that appear in the legend and the table of contents. See Working with the classification legend for more information.
- If you want your graduated symbols to get larger when you zoom in, set a reference scale. Right-click the data frame and click Set Reference Scale. Your symbols will scale as the map's page size is scaled. See Working with data frame reference scales for more information.
- All the symbols should be the same color. Make sure they're dark enough to be seen easily. If you are drawing them inside areas, use a light color to shade the areas.
- Click the Template button to choose another marker symbol. If you click Background, you can choose the fill symbol that will be used behind your graduated symbols.
- If you want to change the maximum sample size, click the Classify button to open the Classification dialog box, then click the Sampling button and type a new value. The maximum sample size is the maximum number of records to be considered for classifying data. Limiting the sample size protects you from reading potentially millions of records.