Draw features classified by value
Some features have numerical attributes, which can be used to display layers showing quantities. The numerical measures used in a layer might represent, for example, a count of population, a ratio of male to female population, or a rank of population density compared to others in the layer. You can display features in a layer classified by the values of numerical attributes, using a number of different classification techniques, and also by using a variety of ways to indicate the different classes.
You can represent quantities on a map by varying colors, such as the colors used in choropleth maps. For example, you might classify a layer of rainfall information using darker shades of blue to represent higher rainfall amounts.
Another alternative to represent map quantity is to use different size symbols. When you draw features classified by size, the quantitative values are grouped into classes. Within a class, all features are drawn with the same symbol. For example, you might classify a layer of population data showing settlements that have larger populations with larger symbol sizes.
To configure features to be drawn classified by value
- In the Layers panel, click the arrow next to the layer you want to configure symbols for. The Layer Details view of the panel appears.
- In the Layer Details view, under Display, click Configure to show the Configure Display view.
Note:The Configure button is only available for feature layers. If you have a layer based on a map service, you can add a sublayer of the map service as a feature layer.
Learn more about adding map service sublayers as feature layers
- In the top drop-down list, choose either Classify Using Color or Classify Using Size.
A default set of symbols is configured automatically for the layer.
- You can change the following settings to configure how features in the layer are split into classifications:
- Click the Attribute drop-down arrow and choose an attribute from the list with which to classify the features.
- Click the Classify using drop-down arrow and choose a mathematical method of classification. Each method has a description to help you choose the most appropriate method for the data you are displaying. If you are not sure which to pick, try experimenting with each method.
- Click the arrows in the Classes text box or enter a number to change the number of classes the layer is classified into if classified by natural breaks, equal interval, or quantile methods. Click the drop-down arrow and choose a value from the Interval Size list if classifying by standard deviation.
- You can then change the following settings to configure how the default features within each classification are displayed:
Classifying by color
- To apply the same symbol to all values, click the All Symbols button, make any changes to the symbol appearance in the All Symbols view, then click the Back button to return to the Configure Display view. This button can be a useful first step in configuring feature display—you can apply the same symbol to all of the features, and then adjust the color, outline or opacity of each symbol individually, or apply a color ramp.
- To apply a different range of colors to the existing symbols, click Color Ramp and choose an option in the Color Ramps view. You can change the sets of colors available from the top drop-down list. Click the Left Arrow button at the top to return to the display options.
- To change the symbol used to draw features within a specific classification, click the arrow next to the value in the list. The Item Information view is shown, where you can change how the symbol is drawn. You can also use the Description text box to change the caption used in the legend for that attribute value.
Classifying by size
- Change the Template Symbol value to define the appearance of the symbol, which is then resized for the different classes.
- To change the symbol used to draw features within a specific classification, click the arrow next to the value in the list. The Item Information view is shown, where you can change how the symbol is drawn. You can also use the Description text box to change the caption used in the legend for that attribute value.
- Change the Start Size and End Size sliders to define the range of symbol sizes used for the different classes.
Changes are shown in the map as soon as you choose different options. Click Done at the top of the panel to return to Layer Details.
Alternatively, you can choose to display features with unique symbols based on an attribute that stores names or categories.