serious? key <- c(1,1,1,2,2,2) val1 <- rnorm(6) indf <- data.frame( key, val1) outdf <- by(indf, indf$key, function(x) c(m=mean(x), s=sd(x)) ) outdf indf$key: 1 m.key m.val1 s.key s.val1 1.0000 0.6005 0.0000 1.0191 ------------------------------------------------------------------------------------------ indf$key: 2 m.key m.val1 s.key s.val1 2.0000 -0.8177 0.0000 0.3978
> as.data.frame(by(indf, indf$key, function(x) c(m=mean(x), s=sd(x)))) Error in as.data.frame.default(by(indf, indf$key, function(x) c(m = mean(x), : cannot coerce class '"by"' into a data.frame /iaw ---- Ivo Welch (ivo.we...@brown.edu, ivo.we...@gmail.com) On Mon, Aug 30, 2010 at 9:36 AM, Henrique Dallazuanna <www...@gmail.com> wrote: > Try this: > > as.data.frame(by( indf, indf$charid, function(x) c(m=mean(x), s=sd(x)) )) > > On Mon, Aug 30, 2010 at 10:19 AM, ivo welch <ivo.we...@gmail.com> wrote: >> >> dear R experts: >> >> has someone written a function that returns the results of by() as a >> data frame? of course, this can work only if the output of the >> function that is an argument to by() is a numerical vector. >> presumably, what is now names(byobject) would become a column in the >> data frame, and the by object's list elements would become columns. >> it's a little bit like flattening the by() output object (so that the >> name of the list item and its contents become the same row), and >> having the right names for the columns. I don't know how to do this >> quickly in the R way. (Doing it slowly, e.g., with a for loop over >> the list of vectors, is easy, but would not make a nice function for >> me to use often.) >> >> for example, lets say my by() output is currently >> >> by( indf, indf$charid, function(x) c(m=mean(x), s=sd(x)) ) >> >> $`A` >> [1] 2 3 >> $`B` >> [2] 4 5 >> >> then the revised by() would instead produce >> >> charid m s >> A 2 3 >> B 4 5 >> >> working with data frames is often more intuitive than working with the >> output of by(). the R wizards are probably chuckling now about how >> easy this is... >> >> regards, >> >> /iaw >> >> ---- >> Ivo Welch (ivo.we...@brown.edu, ivo.we...@gmail.com) >> >> ______________________________________________ >> 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. > > > > -- > Henrique Dallazuanna > Curitiba-Paraná-Brasil > 25° 25' 40" S 49° 16' 22" O > ______________________________________________ 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.
