I have data where where I've taken some measurements three times... twice in rapid succession so I could check test-retest reliability of a piece of equipment, and then a third measurement some time later.
Not I'd like to do an analysis where I have two scores... the first being the mean of the first two taken the same day, and the second being the one taken later. I have a lot of other variables in the row, and I'd like to do the same thing to all of them. Soo.... Data.Frame: Subj Obs MeasureA MeasureB 1 1 45 685 1 2 50 690 1 3 48 693 2 1 39 595 2 2 41 585 2 3 45 343 should become: Subj Obs MeasureA MeasureB 1 1 47.5 687.5 1 2 50 690 2 1 40 590 2 2 41 585 It seems like a job for "aggregate", but I want to collapse on only cases where observation # < 3, and take the mean of a few vars in the aggregation. I can't seem to make it work, and didn't find examples that were on the mark. I think I'm suffering from "prospective interference" and my SPSS syntax knowledge to do exactly this is just getting in my way. any volunteers? I'd very grateful. Thanks! -- --------------------------------------- David L. Van Brunt, Ph.D. mailto:[EMAIL PROTECTED] [[alternative HTML version deleted]] ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
