I need to calculate the number of observations that occur once and twice in the database, without having the value of the observation. I've found some solutions for this already, but only for one condition and I found it difficult to convert the formulas to my needs. A typical data entry looks similar to this:
What I want to do is to find how many clients from a certain group have a certain number of products. My shot this, based on a formula found online, was
where I wanted to see how many clients have two products with numbers 1,2,3,4,6 from group 5.
Unfortunately it failed miserably and I'm stuck.
I would be grateful for every help!
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