On Wednesday 06 February 2008 14:08, Waterman, DG (David) wrote: > Hi, > > I have a data frame consisting of coordinates on a 10*10 grid, i.e. > > > example > > x y > 1 4 5 > 2 6 7 > 3 6 6 > 4 7 5 > 5 5 7 > 6 6 7 > 7 4 5 > 8 6 7 > 9 7 6 > 10 5 6 > > What I would like to do is return an 10*10 matrix consisting of counts > at each position, so in the above example I would have a matrix where, > for example, cell [4,5] contains 2 and [6,7] contains 3. At the moment I > have implemented this using a for loop over the rows of the data frame, > however the data frames I want to process are very long so the loop > takes many minutes to complete. Can I do this in a more efficient way? > > Cheers,
David, have a look at "mapply" (?mapply). This does what you need very quickly. J ______________________________________________ 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.
