How to compute average length of donor relationship in days

[#1]

Hi,

I want to find out how long an average length of a donor relationship is amongst donors that have attrited with at least one payment.

Expression/Variable name at least one payment:

Expression/variable name "attrited" =FadderskapStatus=Stoppdato

Expression/variable name "at least one payment" =InnbetalingsStatus=Har innbetalt

Expression/variable name "start date of donor relationship" == FadderSkapOpprettetDato

Expression/variable name "end date of donor relationship" = FadderSkapSluttDato

Can anyone help me out here?

Best regards,

Christian

[#2]

bump