How to aggregate field results to a chart?
This kind of questions show up quite often. And each time I try to get them resolved with this very first attempt (if it is related to a Views display):


  You may find it easier to start with a "Table" display and convert it to a chart display after setting up the data. It can be easier to visualize what the result of the chart will be if it's been laid out in a table first.


In my experience, 90% of the issues turn out to be related to errors in the creation of the table that contains the data to be charted.

If this question is about creating a chart using the Views integration, then refer to the appropriate Community documentation resources with more details about how to do so:


For the Chart module: Create charts using Views
For the Charts module: Steps to create charts using the views UI.


Disclosure: I'm a (co-)maintainer of both Chart and Charts, and co-author of the documentation resources mentioned.