How To: Symbolize polygons based on the number of intersecting points
The instructions provided describe how to symbolize polygons based on the number of points that intersect or are inside the polygons.
Before symbolizing the appropriate polygon, determine the number of points that intersect with the polygon by joining the points. This creates a new polygon feature class that has a count field representing the number of points that fall inside the polygon.
- Perform a spatial join.a. Right-click the polygon layer, and select Joins and Relates > Join.
b. In the Join Data dialog, select 'Join data from another layer based on spatial location'.
c. Select the desired point layer from the drop-down list to join with the polygon layer.
d. Select 'Each polygon will be given a summary of the numeric attributes'. Also specify the desired methodology for summation, and a location for the output layer.
e. Click OK.
- Export the polygon feature to a new feature class so the join becomes permanent.a. Right-click the polygon feature class > Data > Export Data.
b. Select Yes to add the exported layer to the Table of Contents.
- Symbolize the new polygon feature class based on quantities using graduated colors.a. Right-click the new polygon feature class in the Table of Contents, and click Properties.
b. Select the Symbology tab, and click Quantities > Graduated Colors.
c. Select the field from the drop-down menu (for example, Count) in which the summated values exist.
d. Click OK.
If the error, "Maximum sample size reached" is returned, follow the steps provided in the following Knowledge Base article to resolve the issue.
- ArcGIS Help: About joining and relating tables
- ArcGIS Help: Using graduated colors
- ArcGIS Help: Classifying numerical fields for graduated symbology
- HowTo: Count the number of point features within a polygon