![]() For example, you could represent both city location and population with a graduated symbol. Proportional and graduated symbol maps represent both geographic location and an attribute value for a single location, utilizing a symbol size to represent either an exact value (proportional) or to represent a class of values (graduated). Graduated Symbol and Proportional Symbol Maps When we use the “Equal Interval” classification method, the result is an isopleth map, while all the other methods result in a choropleth map. Choropleth and Isopleth Maps - Graduated Colorsīased upon the frequency distribution of the data, the “Graduated Colors” portion of the Quantities menu utilizes the field’s histogram to set the break values for classification. Once there, select “Quantities” from the “Show” menu and choose one of the four options (choropleth and isopleth are both found under “Graduated colors” and differ based upon the classification method). To display your map as an choropleth, isopleth, proportional symbol, graduated symbol, or dot density map, first open the Symbology tab in the layer’s properties. ![]() Even though we see “Central Heights” twelve times, each three field combination creates a unique value, which each polygon can be symbolized by. There might be then be a feature with a three field combination of “Central Heights, January, 27” and another with a combination of “Central Heights, February, 14”. For example, a layer containing crime data might have a field for the name of the neighborhood and another with month names and a third with reported armed robberies. “Unique Values, Many Fields” will color features based a combination of two or more fields creating a unique value. “Unique values” will color each feature in the layer based on the attributes found in a single field such as two lane roads colored dark grey while four lane roads are colored red. If we wanted to add just a few values to our map, say coloring roads by the number of lanes, we could set the symbology to categories and only add the values for the lane counts we’d like to display. For example, if we want to color each county of Colorado a different color, we can set the symbology to Category, make the value field “County_Name”, add all the values to the list, and set a color ramp. Symbology by Category will allow us to display data based on one or more field. Click on the current symbol to open the Symbol Selector dialog box where you can set the fill color (polygons), outline color (polygons and polylines), or point symbol. The features window will color all of the features the same way.
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