Calculation difficulty


New Member
Hello everyone,

i have the folllowing problem:
I have 4 variables: 1st: Date of onset, 2nd: Date of termination, 3rd: Date of measurement, 4th: measurement. I want to calculate the average of the 4th variable between each period of onset-termination. How can i do it? Each date of onset has an counterpart date of termination. The same applies for the 3rd and 4th variable.
1st & 2nd variables have the same number of incidents. The same applies for 3rd and 4th. But the 2 pairs (1st-2nd & 3rd - 4th) don't have the exact same number of incidents.

Could anyone help over this?

Thanks in advance!