Thanks, BallardW for your interest. No, there are no dummy values in the SAS data. The actual MRNs and dates are all legit and properly sorted. I showed the Excel file example (with dummies) to demonstrate to other SAS users basically how the data were arranged AND how I wanted the PREG values to appear after an algorithm (which I am unable to craft) is applied. I want each EDD (+/- some fuzz) to represent each PREG #. Biologically, if the EDD changes by several months or more, it has to be a new pregnancy (PREG#). So if you could write an algorithm that simply removes the fuzz and makes all the EDDs the same as the first.EDD, then the first few lines of my code should work. For the vast majority of the patients in the data set, the EDD does not change (no fuzz!) and in these cases my code works perfectly. The program I showed DOES fix the first pregnancy, but if a patient had >1 pregnancy in the 7 years worth of data and had the EDD glitch in the second, third, 4th, etc.t, it fails. Hope this makes sense and that you can solve this frustrating puzzle. Thanks again, John Owen
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