Symbology - Classed Colors

The Classed Colors symbology applies line, fill, or symbol fill color to the features in the base layer by class. The features in the base layer are classified by the selected attribute. The colors for each class can be assigned one at a time or a colormap can be used to assign graduated colors across the classes. When used with normalized data, population per area for example, the Classed Colors symbology creates a choropleth map.

The class color is applied to the line color for polyline features.
The class color is applied to the fill color for polygon features. Polygon line color is set on the base layer General page.
The class color is applied to symbol fill color for point features. Point symbol line color is set on the base layer General page.

Select Classed Colors to color features by a classified attribute value.

Properties

The Properties pane includes the properties for selecting the attribute and defining the classes. The Properties pane is in the middle of the Symbology dialog.

Attribute Field

The Attribute field specifies which attribute is used to classify the features in the base layer. Select the desired attribute from the Attribute field list. Only attributes with numeric values are displayed in the Attribute field list when the Classed colors symbology is selected.

The first numeric attribute for the objects in the layer is the default selection in the Attribute field when a symbology is selected for the first time. When a base layer symbology using a numeric attribute is already applied, the Attribute field value is not changed when Classed Colors is selected. The Attribute field changes to the first numeric attribute for the objects in the layer when Classed Colors is selected and the base layer is currently using a text attribute for the current symbology.

Show Missing Values

Select the Show missing values option to include any features that do not have an attribute value for the selected Attribute field in the layer. When the Show missing values option is checked, features that do not have an Attribute field value are displayed, and their properties are controlled by the base layer General page, as well as their individual Line, Fill, and/or Symbol properties.

Clear the Show missing values check box to hide the features that do not have an Attribute field value from the base layer. The features will still be visible in the Contents window, but the features will not be included in the base layer in the plot window.

Features that have an Attribute field value outside the class limits are controlled by the Show all others option. When Show all others is cleared, features with an Attribute field value outside the class limits are treated the same as missing values. When Show all others is selected, features with an Attribute field value outside the class limits are controlled by the All others class properties.

Class Method

The Class method specifies the method used to calculate the limits of the classes. There are five options available: Equal number, Equal interval, Natural breaks , Standard deviation , and User defined. To change the Class method, click on the current option and select the desired option from the list.

Equal number assigns the class ranges such that approximately equal numbers of features are included in each class. Normally in this case, the interval of each class is different.
Equal interval assigns the class ranges so the interval between the minimum and maximum values are equal for each class. Normally in this case, a different number of features is assigned to each class.
Natural breaks uses the Fisher-Jenks algorithm to calculate the ideal natural breaks in the data. Typically these natural breaks are ideal beginnings and endings for data classes. The algorithm is based on Fisher's statement that any optimal classification of data consists of the sum of optimal classes of subsets of the data. To learn more about Jenks' natural breaks data classification method, please refer to Slocum, Terry A. Thematic Cartography and Visualization. New Jersey: Prentice-Hall, 1999.
Standard deviation generates data classes based on the standard deviation of the data.
User Defined allows you to set the >=Minimum value and the <Maximum value for each class individually. This allows you to specify your own ranges for the classes. Ranges defined in this way do not have to be contiguous. To change the >=Minimum or <Maximum value, double-click the values in the class list.

Class Counts

The Class counts value specifies the number of classes there will be on the map. When the Class count value is changed, the classes are automatically updated to reflect the change. To change the number of classes, click the button to increase or decrease Class count or highlight the existing number and type in a new value from 1 to 1000 classes.

Show All Others

Select the Show all others option to include a color for features where the attribute value does not fall within an existing class. Clear the Show all others check box to remove the All others class.

Features that do not have an Attribute field value are controlled by the Show missing values option. When Show all others is not selected, features where the Attribute field value is outside the class limits are treated the same as missing values.

Reverse Color Order

Click Reverse in the Reverse color order field to reverse the colors in the Classes list.

Load/Save Classes

Click Load to load an existing Symbology Color Class (*.colorclass) file. Click Save to save the current classes to a Symbology Color Class (*.colorclass) file. The class limits, names, and colors are saved in the Symbology Color Class (*.colorclass) file.

Colormap for Class

Select the Colormap for class option to apply the Colormap color spectrum colors to the classes. Changing the color of any class in the Classes list automatically clears the Colormap for class check box.

Colormap

The Colormap is the color spectrum that is assigned to the classes. Select a predefined colormap from the Colormap list. Click the to modify or create a colormap in the Colormap Editor.

The Colormap property applies colors to the classes based on class number, not the data value. Therefore the Data section of the Colormap Editor does not have any effect on the class colors by default. We recommend you do not change the Data properties in the Colormap Editor. The first class is always assigned the minimum value color, and the last class is always assigned the maximum value color. Remaining classes are distributed equally across the colormap. The Data properties may change the class colors when Logarithmic scaling is used: The first class is always assigned the minimum value color, and the last class is always assigned the maximum value color. The remaining classes are distributed logarithmically across the colormap.

Classes

The Classes list displays the class color (Color), upper limit (<= Upper Value), proportion (%), count (Count), and class name (Name) for the classes. The Classes listis on the right side of the Symbology dialog.

Changing the Class Color

The Color column displays the colors for the classes. Click the color preview in the Color column to change the color for the class. The Color Properties dialog is displayed.

Specify the class Color and Opacity in the Color Properties dialog.

Specify the class color by selecting a predefined color from the color palette in the Color field, or click to select a color in the Colors dialog. Set the class opacity by clicking and dragging the slider or typing a value between 0 and 100 in the Opacity field. An Opacity of 100% is completely opaque. An Opacity of 0% is completely transparent.

Changing the Class Limits

The <= Upper Value column displays the upper limit for each class. The first class in the Classes list has no lower limit. Subsequent classes use the prior class upper limit for a class minimum. For example, in the image above Class 2 includes values greater than 28160 (Class 1's upper limit) and less than or equal to 159064.

The class limits are automatically calculated when the Class method is Equal number, Equal interval, Natural breaks, or Standard deviation. The class limits must be individually defined when the Class method is User defined. Changing a class <= Upper Value automatically updates the Class method to User defined.

Type the desired class maximum in the <= Upper Value column to change the upper limit for a class. The proportion and count statistics are automatically updated when the <= Upper Value is changed.

Statistical Information about the Features in Each Class

The Classes list displays summary statistics for each class. The % and Count columns display statistical information about the class. The % column indicates the percentage of features in the particular class. The Count column indicates the number of features included in each class. These values cannot be directly edited and are for informational purposes only.

Changing the Class Name

The Name column displays the class names. Specify a class name in the Classes list to display class names in a legend. By default, classes are named Class 1, Class 2, etc. Type a name in the Name column to change the class name.

OK, Cancel, and Apply

Click OK to save your changes, close the Symbology dialog, and update the base layer symbology. Click Cancel to close the Symbology dialog without making changes to the base layer symbology. Click Apply to apply your changes to the base layer while keeping the Symbology dialog open.