From: Gabor Grothendieck <ggrothendieck_at_gmail.com>

Date: Tue 31 Jan 2006 - 21:55:25 GMT

R-devel@r-project.org mailing list

https://stat.ethz.ch/mailman/listinfo/r-devel Received on Wed Feb 01 09:10:25 2006

Date: Tue 31 Jan 2006 - 21:55:25 GMT

I think that a pointer to ?formula needs to be added to ?":"

On 1/31/06, Liaw, Andy <andy_liaw@merck.com> wrote:

*> ":" in a formula is not the same as ":" otherwise!
**>
**> Andy
**>
**> From: Ionut Florescu
**> >
**> > a:b means - all the element in the vector from a to b
**> > a[,-1] means for the matrix a keep all the rows but not the last or
**> > first -can't remember column.
**> > When in doubt do what I do make a small matrix and apply the
**> > command see
**> > what it does.
**> > After this:
**> > > a=matrix(c(1:9),3,3)
**> > > a[,-1]
**> > [,1] [,2]
**> > [1,] 4 7
**> > [2,] 5 8
**> > [3,] 6 9
**> >
**> > you see that -1 eliminates the first column.
**> > I found the R manual useless myself.
**> > The only thing useful is the search function in the html
**> > help. That has
**> > examples.
**> >
**> > Ionut Florescu
**> >
**> > Michael wrote:
**> > > Hi all,
**> > >
**> > > R is so difficult. I am so desperate.
**> > >
**> > > What does the ":" mean in the following statement?
**> > >
**> > > What does the "[, -1]" mean?
**> > >
**> > >
**> > >> # Leaps takes a design matrix as argument: throw away the intercept
**> > >> # column or leaps will complain
**> > >>
**> > >> X <- model.matrix(lm(V ~ I + D + W +G:I + P + N,
**> > election.table))[,-1]
**> > >>
**> > >
**> > > Thanks a lot!
**> > >
*

> > > [[alternative HTML version deleted]]

*> > >
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**> > >
**> > >
**> >
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**> > PLEASE do read the posting guide!
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**> >
**> >
**>
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https://stat.ethz.ch/mailman/listinfo/r-devel Received on Wed Feb 01 09:10:25 2006

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