You should be able to chart your values directly from a layout based on either Search_Category or Search_OFATR.
If you base it on Search Category, you can use Count ( Search_OFATR::_kf_CategoryID ) as the calculation for your Y-Axis.
If you base it on Search_OFATR, the Y-axis can be specified as a "count" summary field and you can specify "found set, groups of values when sorted" in your data source settings. The records must then be sorted by Search_OFATR::_kf_CategoryID to get one bar for each category.
Both options work for what you describe, but the second option allows you to perform finds to further control exactly what records get counted in each category.
I've gotten the first one to workout (Layout based on Search_Category).
The screenshot shows my attempt at the second. I cannot get the graph to sum up similar records within Search_OFATR.
Would I be able to create this graph with a layout based on Search_Overwatch?
Your y-axis data series must be changed to refer to a summary field defined in Search_OFATR.
I must be missing something. The field is a summary field based on "count" but the graph doesn't change.
Are the records in your found set sorted or unsorted? They should be sorted by category.
That was it. Thanks PhilModJunk.