To help you get started with developing expressions here are sample charts and their metric expressions.
Finding the Average of a Series
Replacing Metric Names with Property Name
Generating a Complex Expression Tree with Multiple Functions
For each chart you are walked through the Expression Builder process. The instructions are based on the expressions used for each chart. Adjust as appropriate for your chart.
As each selection is made, another drop-down list opens prompting you for another metric property or filter value key-value pair. To end the Expression Builder process, press the ENTER key.
Note: These examples are for illustrative purposes - your installation may not have the same key-value pairs.