Thanks, Gabor. Works great!
On Thu, Jun 25, 2009 at 10:38 AM, Gabor Grothendieck <
ggrothendi...@gmail.com> wrote:
> Try this (shown for stated problem but generalizes by just adding
> additional arguments):
>
> mapply("[", list(x), ltrs, mnths)
>
>
> On Thu, Jun 25, 2009 at 10:24 AM, Rama Ramakrishnan<r...@alum.mit.edu>
> wrote:
> > Follow-on question: is there a way to do this for higher-dimensional
> (i.e.
> > more than 2 dimensions) arrays?
> >
> >
> > On Thu, Jun 25, 2009 at 10:17 AM, Rama Ramakrishnan <r...@alum.mit.edu
> >wrote:
> >
> >> That works!! Very nice way to do it! Thank you, Henrique!
> >> Rama Ramakrishnan
> >>
> >>
> >> On Thu, Jun 25, 2009 at 10:11 AM, Henrique Dallazuanna <
> www...@gmail.com>wrote:
> >>
> >>> Try this:
> >>>
> >>> y$values <- diag(x[y$ltrs, y$mnths])
> >>>
> >>> On Thu, Jun 25, 2009 at 11:02 AM, Rama Ramakrishnan <r...@alum.mit.edu
> >wrote:
> >>>
> >>>> Dear R-Users,
> >>>> I need to lookup values from a 2-d table using the row names and
> column
> >>>> names as indices. I was wondering if there's a way to do this without
> an
> >>>> explicit loop.
> >>>>
> >>>> Example:
> >>>> #x is the 2-d table that holds the values
> >>>>
> >>>> x <- matrix(rnorm(26*12),nrow=26)
> >>>>
> >>>> rownames(x) <- letters
> >>>>
> >>>> colnames(x) <- month.name
> >>>>
> >>>>
> >>>> #y is a data frame that has the "keys" I want to use as indices into x
> >>>>
> >>>> y <- data.frame(ltrs=sample(letters,5),mnths=sample(month.name
> >>>> ,5),values=0)
> >>>>
> >>>>
> >>>> #I want to fill in the "values" column using the "ltrs" and "mnths"
> >>>> columns
> >>>> as keys to look up
> >>>>
> >>>> # the associated value from x
> >>>>
> >>>> #One way to do this is with a FOR loop
> >>>>
> >>>> for (i in 1:nrow(y)) {y$val[i] <- x[y$ltrs[i],y$mnths[i]]}
> >>>>
> >>>>
> >>>> My question: Is there a more efficient way (e.g., one without using an
> >>>> explicit loop) to do this?
> >>>>
> >>>>
> >>>> Thanks in advance!
> >>>>
> >>>>
> >>>> -Rama Ramakrishnan
> >>>>
> >>>> [[alternative HTML version deleted]]
> >>>>
> >>>> ______________________________________________
> >>>> 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
> >>>
> >>
> >>
> >
> > [[alternative HTML version deleted]]
> >
> >
> > ______________________________________________
> > 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.
> >
> >
>
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