How To: Generate a Frequency table based on two fields in ArcMap 8.x
Instructions provided describe how to generate a Frequency table based on two fields in ArcMap 8.x. A Frequency operation generates an output table containing a frequency calculation for each attribute value combination of the specified field. For example, given a point layer of world cities, containing CNTRY_NAME and POP_RANK fields, a frequency operation would provide a count of how many cities of each population rank exist in each country.
In ArcInfo Workstation and in ArcGIS 9.x, there is a Frequency tool that performs this type of multiple field frequency. However, in ArcGIS 8.3 or when operating under the ArcEditor or ArcView licenses of ArcGIS 9.x, this option does not exist. In these cases, multiple field frequency calculations can be accomplished in the geodatabase by using the underlying database to execute a query that will return this information. The following example describes creating such a query in Microsoft Access.
Follow the steps below.
- Load the shapefile for example, world cities, into a personal geodatabase.
- Open the personal geodatabase in Microsoft Access.
- Click Database Objects > Queries from the View menu.
- Double-click 'Create query by using wizard'.
- Add the fields to be used for the frequency counts to the Selected Fields list for example, CNTRY_NAME and POP_RANK.
- Click Next.
- Select 'Summary.' when querried: "Would you like a detail or summary query?".
- Click Summary Options.
- Check Count records in <Table Name> check box.
- Click OK.
- Click Finish.
A query summarizing the count of records that have unique combinations of the fields specified is now available.
The advantage of generating this information through a query is that it automatically is updated as the data in Access is updated. Add this query to ArcMap using an OLE DB connection to the Access database.