I am trying to configure my pie charts to not show "undefined categories." I can't seem to turn them off in the "Slices" Tab of the Pie Chart settings. Does anyone know how to choose only the fields that they want to display in the pie chart?
You can't remove undefined categories, however you can filter them out. In the data options of your pie chart add a filter that only includes the values you are defining in the chart. That way you will never have an undefined value.
Filtering is your best option. You can also just delete the slice itself in the Slices area: