[R] data frame search

[Gabor Grothendieck]

which is part of base R so look again.

On 6/24/06, Bart Joosen <bartjoosen at hotmail.com> wrote:
> Thanks, couldn't find this function,
>
> Best regards
>
> Bart
>
> ----- Original Message -----
> From: "Gabor Grothendieck" <ggrothendieck at gmail.com>
> To: "Bart Joosen" <bartjoosen at hotmail.com>
> Cc: <r-help at stat.math.ethz.ch>
> Sent: Saturday, June 24, 2006 1:15 PM
> Subject: Re: [R] data frame search
>
>
> > Try this:
> >
> > which(DF1 == 4, arr.ind = TRUE)
> >
> >
> > On 6/24/06, Bart Joosen <bartjoosen at hotmail.com> wrote:
> >> Hi,
> >>
> >> I want to make a data frame which contains the positions of some searched
> >> values in another data frame.
> >>
> >> Like:
> >> Dataframe 1:
> >>
> >> 1  2  3  4  1  2  3  4
> >> 2  3  4  1  2  3  4  2
> >> 4  1  2  3  2  3  4  1
> >>
> >> Let's say I searched on "4", then Dataframe 2 should contain:
> >> x  y
> >> 1  4
> >> 1  8
> >> 2  3
> >> 2  7
> >> 3  1
> >> 3  7
> >>
> >> I have written a routine, but it seems to me that it isn't that perfect:
> >> x<- 0
> >>
> >> y<- 0
> >>
> >> for (j in 1:ncol(df)) {
> >>
> >> for (i in 1:nrow(df)) {
> >>
> >> if (df[i,j] == 3) {
> >>
> >> x <- c(x,i)
> >>
> >> y <- c(y,j)
> >>
> >> }
> >>
> >> }
> >>
> >> }
> >>
> >> df2 <- data.frame(x,y)
> >>
> >> df2 <- df2[-1,]
> >>
> >> Can someone come up with an elegant/faster solution, because the ultimate
> >> goal of this routine is to analyze an jpg image.
> >>
> >> Kind regards
> >>
> >> Bart
> >
>