Hi Shmuel, Many thank for your reply. However, there is still a problem if I am running the code. it is making all my missing as 0. Whereas, If the row after missing has 1, I want 1 - 1=0, whereas, if the row after missing has 2, I want 2-1=1. The code you mentioned below is doing like this: If the scenario like this: Patient id Parity Date of birth 5 . 5/1/2005 5 2 9/11/2007 5 3 1/1/2009 This is what the code is doing. Patient id Parity Date of birth 5 0 5/1/2005 5 2 9/11/2007 5 3 1/1/2009 Whereas, I want like this: Patient id Parity Date of birth 5 1 5/1/2005 5 2 9/11/2007 5 3 1/1/2009 So, whether it 1, 2, or 3 what ever is after missing row in parity, I want to subtract 1 from it. Many thanks for your help
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