Can you create a new calculated field that is:
If not, are you able to post a sample workbook?
Unfortunately Purchases and Views isn't available because they're under the "event" dimension. The data pull looks like this
Date Event Values 1/1/2013
75 1/2/2013 Views 82 1/1/2013 Purchases 25 1/2/2013 Purchases 40 1/3/2013 Views 90 1/3/2013 Purchases 65
You have to create two calculated fields.
Purchases=If [Event]='Purchases' then [Values] End
Views=If [Event]='Views' then [Values] End
then do the third calculation conversion = Sum(Purchases)/Sum(Views)
Please find the attached workbook.
Purchases-Views_ID.twbx 16.4 KB