This may be a basic question but it has been difficult to find a solution on my own.   I have data that is organized into multiple groups, including trial, treatment, and replication. I wish to create a new variable for the entire data set using values from an observation presently assigned to a given treatment within a trial and replication (for later use as a covariate). This new variable should be assigned to all other observations with a given trial and replication.   Here is what I current have:   Data Have; Input Trial Treatment Replication VariableX; datalines; 1 1  1 a 1 1  2 b 1 2  1 c 1 2  2 d 1 3  1 e 1 3  2 f 2 1  1 g 2 1  2 h 2 2  1 i 2 2  2 j 2 3  1 k 2 3  2 l ;   This is what I want:   Data Want; Input Trial Treatment Replication VariableX VariableY; datalines; 1 1  1 a a 1 1  2 b b 1 2  1 c a 1 2  2 d b 1 3  1 e a 1 3  2 f b 2 1  1 g g 2 1  2 h h 2 2  1 i g 2 2  2 j h 2 3  1 k g 2 3  2 l h ;   Any help would be greatly appreciated. ... View more