Hi all, I'd aprpeciate any help on how to solve this problem. My SAS data set has three variables - a unique (person) identifier, a date, and a metric I need to sum up (Points). Below is some (dummy) sample data: ID Date Points 111 15-Feb-2013 100 111 28-Mar-2013 200 111 17-Nov-2013 100 111 14-Apr-2014 50 111 18-May-2014 100 112 17-Jun-2012 250 112 04-Apr-2013 100 112 28-Aug-2013 100 Now what I need to produce is a data set that contains the same number of rows as the above data set, but sums up the Points retrospectively based on the past Date values. In other words what I need to do is cumulatively sum Points for every data row, but for all Dates that occur <= 12 months from the current value of Date. This would be a new variable, say Cumulative_12m_Points Below is what I am trying to build based on the above data set: ID Date Points Cumulative_12m_Points 111 15-Feb-2013 100 100 111 28-Mar-2013 200 300 111 17-Nov-2013 100 400 111 14-Apr-2014 50 150 111 18-May-2014 100 250 112 17-Jun-2012 250 250 112 04-Apr-2013 100 350 112 28-Aug-2013 100 200 So the Cumulative_12m_Points variable sums up Points for the last 12 months based on Date (for each ID). Any help appreciated! Regards, GreenMan1972
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