Hi Nitin, In Ferret, missing + variable = missing. (This is true for all operations, and it's probably more intuitive if you think, what should be the result if you were multiplying or dividing the variables? Missing*2 = ?) If you want to have the sum contain any values that do exist then you'll need to fill in any missing data with zero's. Either define new variables with an IF statement like let gp1var = if gp1 then gp1 else 0and add those, or you could use the MISSING function to substitute 0 where either variable is missing. let sum = MISSING(gp1, 0) + MISSING(gp2, 0) Ansley On 8/19/2014 1:33 AM, Nitin Patil
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