A lot of examples using mashups: Web Apps from Qlik Sense
You can accomplish this by creating an inline table in the data load editor. Once created, you can reference the field in a List Box (or however you should decide), thus creating your button. In your chart, you would simply use a measure defined in this inline table.
Inline table script would look as follows: (may require some manipulation to get your data in this format)
//For use with inline table
SET hideprefix = '%';
LOAD * Inline [
Field to be used in your List Box (button) object: [gives you the option to select "Actual" or "Base"]
Dimension for your chart(s) can be whatever you decide.
Measure for your chart(s): [toggles the measure of your charts based on what button you have selected]
I hope this helps!