Does this do what you want? > x <- read.table(textConnection("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"), header=TRUE) > counts <- ave(seq(nrow(x)), x$B, x$C, x$D, FUN=length) # get counts > x.new <- x[, -1] # delete "A" > x.new$FreqD <- counts # add new column > # print out unique entries > unique(x.new) B C D FreqD 1 B1 C1 D1 3 2 B2 C1 D1 3 4 B2 C2 D2 2 7 B1 C2 D2 2 >
On Jan 7, 2008 2:38 PM, Gang Chen <[EMAIL PROTECTED]> wrote: > 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. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? ______________________________________________ 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.