Use the Report Summary Formula PrevGroupVal to compare metrics between peer groups. For instance use it to compare won amounts over successive periods such as month-on-month comparisons.
To do this create a Report grouped by Close Date. The dates must be grouped by the period you require such as by Month or Quarter. Or you could use Close Month, Fiscal Period, etc.
Order the Groups in ascending date order so that comparison formula makes sense.
Create a Report summary field using PREVGROUPVAL which shows the amount variance compared to the previous period as a percentage. PREVGROUPVAL uses these parameters:
PREVGROUPVAL(summary_field, grouping_level [, increment]) where the
Summary_Field is the name of the grouped row or column (like AMOUNT:SUM). Grouping_Level is the summary level (such as CLOSE_DATE)
The formula is:
(AMOUNT:SUM – PREVGROUPVAL(AMOUNT:SUM, CLOSE_DATE)) / PREVGROUPVAL(AMOUNT:SUM, CLOSE_DATE)
Set the Display level to specific groups
Run the report which will now include the month-on-month variance as a percentage.
Add a Chart with a line chart to represent the variance to appreciate the full effect of the comparison.