displaying Differences between averages formula

[CromwellF]

I have a collection of data that is grouped against dates. For these dates I need to return the averages of the data related to date. This I can do quite happily, however as the dates increase through the range reported against I also need to output of the difference between the first date average and the second date average, then 2nd and 3rd and so on.

 

[lbass]

Create three formulas:

//{@reset} to be placed in the group (date) header_b section (insert this section and then suppress it):
whileprintingrecords;
numbervar sumamt := 0;
numbervar prevave := 0;
numbervar counter := 0;

//{@prevave} to be placed in the detail section:
whileprintingrecords;
numbervar sumamt := sumamt + {table.amount};
numbervar counter := counter + 1;
numbervar prevave;

prevave := sumamt/counter

//{@diff} to be placed in the group header_a section:
whileprintingrecords;
numbervar prevave;

prevave - average({table.amount},{table.date})

-LB