Yes, this chart can now be customized. To change the Trend metric that is shown, select the Change Metric link by the pencil icon.
A menu will pop up showing the options you can choose from. For details on how each metric is calculated, please see this FAQ. Make your selection and click Select Chart.
After your new metric is selected, you may need to manually refresh the chart by using the click here link in the refresh message.
You can also customize your Portfolio Views dashboard to show whatever metrics you'd like. See this FAQ to customize your dashboard.
Also, if you have more than 1,000 properties, this graph will not be displayed. Because the graphs are generated in real time, the graph was causing performance issues for large portfolios. We are working on a longer term solution.