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How To: Aggregate data for points in a polygon

Procedure

The following example finds how many stores are within a specific ZIP code area, aggregates the data for each record and puts it in a new column. This will show how many points are in each polygon.

Solution:

1. Open the zipcode.agf file
2. Open the geocoded point.dbf file
3. Click Table > Aggregate Data
4. In the Aggregate Data dialog box, calculate Data For 'layer - zipcode.agf'. Leave Update Selected Features box unchecked.
5. For Copy Feature Count To, click New Table and name the table under file name to 'count'.
6. Click Define New Table
7. Create a column to hold the count and make sure Type is defined as a number.
8. Click Links To Geo 'layer - zipcode.agf' and 'key column - id'
9. Click OK. You should now be back to the Aggregate Data dialog box.
10. Select the newly created column, in this case 'count', under Copy Feature Count To.
11. Under Aggregating Data From (layer - point.dbf), leave selected features only box unchecked and options as is.
12. Click OK

There should now be a table linked to the geo file. The table should show the new column at the right side of the table with the number of points for each ZIP code polygon. You can use this data to show a theme map with a different color shade for each polygon based on the number of points in that polygon.

To aggregate all columns, do the following:

1. Select the buffer and query inside it.
2. Click Aggregate Data
3. Calculate data for the buffer
4. Click Update Selected Features Only
5. Click New Table
6. Assign a name the new table.
7. Click Copy Columns and select the point table
8. Click Links to Geo and link it to the buffer.agf
9. Aggregate from the table.
10. Click Using Selected Features Only
11. Click Aggregate to All Containing Features
12. Click OK

When you open the table you will see one record and totals for all numeric columns.

Note: Use Excel to aggregate a single column.