column statistics
Use aggregate:
aggregate(x['Value'], x[c('Factor1', 'Factor2')], mean)
On Mon, Dec 7, 2009 at 8:25 AM, Ivan Calandra
<ivan.calandra at uni-hamburg.de> wrote:
Hi everybody, I would like to compute the mean for 1 variable between the rows with the same levels. For example, with the dataset below: Factor1 ? ? ?Factor2 ? ? ?Value A ? ? ? ? ? ? ? X ? ? ? ? ? ? ? 1 A ? ? ? ? ? ? ? X ? ? ? ? ? ? ? 2 A ? ? ? ? ? ? ? Y ? ? ? ? ? ? ? 3 A ? ? ? ? ? ? ? Y ? ? ? ? ? ? ? 4 B ? ? ? ? ? ? ? X ? ? ? ? ? ? ? 5 B ? ? ? ? ? ? ? X ? ? ? ? ? ? ? 6 B ? ? ? ? ? ? ? Y ? ? ? ? ? ? ? 7 B ? ? ? ? ? ? ? Y ? ? ? ? ? ? ? 8 I would like to get: Factor1 ? ? ?Factor2 ? ? ?Value A ? ? ? ? ? ? ? X ? ? ? ? ? ? ? 1.5 A ? ? ? ? ? ? ? Y ? ? ? ? ? ? ? 3.5 B ? ? ? ? ? ? ? X ? ? ? ? ? ? ? 5.5 B ? ? ? ? ? ? ? Y ? ? ? ? ? ? ? 7.5 Up to now, I worked in Statistica and Systat, and it was called "column statistics" in Statistica (and I had a script with the "BY" function in Systat). Of course it is a simplified case. For my dataset I have 4 factors and 15 variables, so a general method would be nice. However, my skills are not that great, so if you could please give some explanations (I mean other than what is in the ?function of course). Thanks a lot in advance Ivan
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