Sorry, word wrap made that incomprehensible, I think
x y
4 5
6 7
6 6
7 5
5 7
6 7
4 5
6 7
7 6
5 6
dat <- read.table('clipboard', header=TRUE)
dat$patt <- paste(dat$x,dat$y, sep='')
mm <- as.data.frame(with(dat, table(patt)))
dat <- merge(dat, mm, by='patt')
mat <- matrix(0, ncol=10, nrow=10)
gg <- matrix(c(dat$x, dat$y), ncol=2)
mat[gg] <- dat$Freq
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of Doran, Harold
> Sent: Wednesday, February 06, 2008 9:56 AM
> To: Waterman, DG (David); r-help@r-project.org
> Subject: Re: [R] counting row repetitions without loop
>
> I think this does what you want, but there may be a more efficient way
>
> x y
> 4 5
> 6 7
> 6 6
> 7 5
> 5 7
> 6 7
> 4 5
> 6 7
> 7 6
> 5 6
> dat <- read.table('clipboard', header=TRUE) # copy sample
> data above dat$patt <- paste(dat$x,dat$y, sep='') mm <-
> as.data.frame(with(dat, table(patt))) dat <- merge(dat, mm,
> by='patt') mat <- matrix(0, ncol=10, nrow=10) gg <-
> matrix(c(dat$x, dat$y), ncol=2) mat[gg] <- dat$Freq
>
> > -----Original Message-----
> > From: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED] On Behalf Of Waterman, DG
> > (David)
> > Sent: Wednesday, February 06, 2008 9:08 AM
> > To: r-help@r-project.org
> > Subject: [R] counting row repetitions without loop
> >
> > 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
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and provide commented, minimal, self-contained, reproducible code.
