How can I select features in one layer that fall within a single feature of another layer?
You can use the Query menu tool.
The following example will demonstrate this process:
Question: How many counties fall inside California?
1. Open the County.agf. This geo file has both county and state boundaries in it.
(Make sure that County:states is your only default layer set.)
2. Select California. This is the feature you will query against.
3. Go to Query | Select by Location | Inside.
4. In the selection box, for the 'Select Features From:' item, select County:counties, since you are trying to determine (select) how many counties fall within the selected feature, California.
5. For the 'Located Inside Features From:' item, select County:states. This is the layer that contains the selected feature, California. Click OK.
6. You will get a number of selected features at the bottom of the map in the
status bar. In this example, note that there are 59 counties selected, since 59 counties fall within California.
From here, you can either save this query as a geo file using File | Save as, or
you can save the counties as a separate layer using Edit | Copy to Layer.
If you use Copy To Layer, the currently selected features in Copy Features From, will be selected. (Be sure to check the box "Selected Features Only").
Then select the layer you want to Copy Features To.
Click on the New Layer button to create the New Layer.
If you have a Table linked to the geo file, you will have the opportunity to
create a new table as well.
Click OK to finish copying to layer.
You now have a layer containing the counties of California.