Trouble calculating the average

[#1]

Im not sure if the output I want is possible I hope it is so here goes.

I have a field which calculates the difference between two times.

At present the information outputted is only correct if I have only one day selected.

Is it possible to display the average for a months set of data but then the actual sum for a single day

[jfkinspari]

The aggr function calculates the

sum(CHKS)-sum(SCH)

per possible combinations of FlightNo and Date (this should be equilliant to the unique departure) The result will be a string of numbers like this

6.2,3,1.2,10,4

You can then use any aggreation function, like sum, avg or stddev, to transform the result into on single value.