Selecting Locations with Multiple Rows

When there are multiple cases for a single location–that is, multiple data rows for a single pair of unique latitude and longitude coordinates–this may not be apparent from the map because of overplotting of symbols. The multiple rows at a location can be seen in the data table, but identifying them may not be easy.

One of the ways to identify co-located data is to use the Selections / Co-located Data menu item to select and highlight those locations on the map and in the data table. This menu item will display the following dialog.

The dialog for selecting co-located data

This dialog allows locations with multiple data values, or locations with only a single data value, to be easily selected and highlighted on the map and in the table. Locations can be selected that have more than, less than, or exactly a specified number of data values.

Below the prompts for data selection criteria is a drop-down list that specifies the action to be taken with the results of the data selection. The available actions are:

  • Replace: All currently selected data are replaced with the newly selected data.

  • Union: The results of the new data selection will be added to any previously-selected set of values.

  • Intersection: Only the table rows that are in both the previously-selected set and the newly-selected set will be retained.

  • Difference O-N: The results of the new data selection (New) will be subtracted from any previously-selected set of values (Old).

  • Difference N-O: The set of previously-selected values (Old) will be subtracted from the newly-selected set of values (Nnew).

The Replace action is the default.

When the ‘OK’ button is selected, the selection criteria will be evaluated. If it is invalid, an error message will be displayed. If it is valid, the selected data values will be updated in the table and on the map.