Hi,

Say I have a following data

ID   Week    Event_Occurence
A 1 0
A 2 0
A 3 1
A 4 0
B 1 1
B 2 0
B 3 0
B 4 1

that whether an individual experienced an event in a particular week.

I wish to create list such as the first element of the list will be a
vector listing the week number when the event has occurred for A, followed
by that of B.

Can you help creating this?

-- 
Anindya Sankar Dey

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