Hi Urvish, You are right, most of the times GROUPFORMAT would be used with SET statement. Actually I used GROUPFORMAT for only a few times. I ran into this issue when trying to answer someone else's question about merging data sets. While merging, variables from data sets would not be set to missing at the beginning of each iteration of data step. Of course, at the beginning of the first iteration, all variables would be initialized as missing when no data has been read from data sets. Thank you very much for spending time on this!
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