First, there are some years that don't appear. For example, Patient X has no data for 2005. Can we assume that smoker=no for those years? (If not, how do we determine smoking status?) Yes, you can assume smoker = no for those years. "Clearly, you want to flag this combination: delivery=yes, smoker=yes, and smoker=yes for the previous year." I am hoping for delivery = yes and (smoker=yes OR smoker for previous year = yes) Did you also want to flag: delivery=yes, smoker=no, but smoker=yes for the previous year? YES Did you also want to flag: delivery=yes, smoker=yes, but smoker=no for the previous year? YES
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