Yes, I misstated it when I said that I would keep B and C. I want to collapse column A, but count the frequency of D as a new column in the new dataframe DF2 while collapsing A. The rows of columns B, C, and D of course would be reduced because of A collapsing.
For example, if dataframe DF is A B C D A1 B1 C1 D1 A1 B2 C1 D1 A1 B1 C1 D1 A1 B2 C2 D2 A2 B1 C1 D1 A1 B2 C2 D2 A1 B1 C2 D2 A2 B2 C1 D1 A1 B1 C2 D2 A2 B2 C1 D1 ...... I would like to have a new dataframe DF2 B C D FreqA B1 C1 D1 6 B1 C1 D2 31 B1 C2 D1 8 B1 C2 D2 14 B2 C1 D1 12 B2 C1 D2 43 B2 C2 D1 23 B2 C2 D2 43 Thanks, Gang On Jan 7, 2008, at 2:06 PM, Duncan Murdoch wrote: > On 1/7/2008 1:28 PM, Gang Chen wrote: >> I have a dataframe DF with 4 columns (variables) A, B, C, and D, >> and want to create a new dataframe DF2 by keeping B and C in DF >> but counting the frequency of D while collapsing A. I tried >> by(DF$D, list(DF$B, DF$C), FUN=summary) >> but this is not exactly what I want. What is a good way to do it? > > I think you can't do that. If you want to keep B and C, then you > can't reduce the number of rows, but "collapsing A" sounds like you > want fewer rows. > > Perhaps if you posted a simple before and after example? > > Duncan Murdoch ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.