Re: [R] Help! What does this R command mean?

From: Liaw, Andy <andy_liaw_at_merck.com>
Date: Wed 01 Feb 2006 - 08:44:49 EST


":" 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]]
> >
> > ______________________________________________
> > R-help@stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
> >
> >
>
> ______________________________________________
> R-help@stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
>
>



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Feb 01 09:03:06 2006

This archive was generated by hypermail 2.1.8 : Fri 03 Mar 2006 - 03:42:16 EST