Step 1: Getting started
To create charts in Drupal, you can (also) use the Charts module. It comes with a sample view which will give you a chart for each of your content types.
Just clone and refine that view, and check how close you are to make it fit your needs. Refer to Create charts using Views (and its subpages) for more details.
For a sample of such chart (derived from the delivered sample view), have a look at this demo sample.
Step 2: Create the tabular format of the view
A common mistake when creating charts, is that the data to be charted is (not yet) correct. So you really need to first work on getting the tabular format of the view created correctly. That's also what's recommended in the Bonus tip within Steps to create charts using the views UI, i.e.:
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. ...
Step 3: Add the chart to your view
Do not try to start this step if you didn't first complete the prior step.
Just use the views display format "Charts", and select the various options that fit your needs. Refer to Steps to create charts using the views UI for detailed instructions about this.
Disclosure: I'm a (co-)maintainer of the Charts module.