From: Liaw, Andy <andy_liaw_at_merck.com>

Date: Wed 01 Feb 2006 - 08:44:49 EST

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

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
*