Thanks very much!

Gurpal
Centrica Energy.

On Wed, Oct 28, 2009 at 4:31 PM, William Dunlap <wdunlap@tibco.com> wrote:

> > -----Original Message-----
> > From: r-help-bounces@r-project.org
> > [mailto:r-help-bounces@r-project.org] On Behalf Of Erik Iverson
> > Sent: Wednesday, October 28, 2009 9:22 AM
> > To: Gurpal Kalsi; r-help@r-project.org
> > Subject: Re: [R] Selecting rows according to a column
> >
> > Hello,
> >
> > Here's an idea:
> >
> > ifelse(z$c == "a", z$a, z$b)
>
> If there may be many columns to select from (so
> the nested ifelse's become tedious) one might try
>   > z[,-3][cbind(seq_len(nrow(z)),z$c)]
>   [1]  1  2 30 40 50
> The initial [,-3] is there only so when the data.frame
> is converted to a matrix by [.data.frame's processing
> of a matrix subscript it becomes a numeric matrix, not
> a character matrix.
>
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
>
> >
> >
> > > -----Original Message-----
> > > From: r-help-bounces@r-project.org
> > [mailto:r-help-bounces@r-project.org]
> > > On Behalf Of Gurpal Kalsi
> > > Sent: Wednesday, October 28, 2009 11:15 AM
> > > To: r-help@r-project.org
> > > Subject: [R] Selecting rows according to a column
> > >
> > > Hi,
> > >
> > > With a data such as:
> > > > z = data.frame(a = 1:5, b=10*a, c = c("a", "a", "b", "b", "b") )
> > > * a  b  c*
> > >  *1* 10 *a*
> > >  *2* 20 *a*
> > >  3 *30* *b*
> > >  4 *40* *b*
> > >  5 *50* *b*
> > >
> > > Can anyone suggest a way to select [1, 2, 30, 40, 50],
> > > ie. using column "c" to specify which column is selected
> > for each row.
> > >
> > > Many thanks
> > >
> > > G
> > >
> > >     [[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.
> >
> > ______________________________________________
> > 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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