Im hoping someone can help.
I am looking to find the sum of all sickness within the last 12 rolling months.
I want to add sum instances of sickness after a certain date. I have placed an example of my data set below.
Dates
01/01/2011 S
02/01/2011
03/01/2011
04/01/2011 S
05/01/2011
So if I was searching all sickness after 02/01/2011 i would need the result to be 1.
Can anyone help?
Matt
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