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]]
RTFM! Especially the Introduction to R tutorial. Type help.start() at the prompt. It should open your web browser. Choose "Introduction to R". Only then will you attain enlightenment. Simon. 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 at 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 > >-- Simon Blomberg, B.Sc.(Hons.), Ph.D, M.App.Stat. Centre for Resource and Environmental Studies The Australian National University Canberra ACT 0200 Australia T: +61 2 6125 7800 email: Simon.Blomberg_at_anu.edu.au F: +61 2 6125 0757 CRICOS Provider # 00120C
?":" ?"[" Also try ?"?" Also 1. read the "An Introduction to R" manual. On R Home page click on Manuals under Documentation in the left hand column. 2. go to: http://cran.r-project.org/other-docs.html and read your choice of documents. 3. print out this reference card and keep it handy: http://www.rpad.org/Rpad/R-refcard.pdf On 1/29/06, Michael <comtech.usa at gmail.com> 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 at 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 >
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 at 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
>
>
":" 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 at 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 at 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 > >
I think that a pointer to ?formula needs to be added to ?":" On 1/31/06, Liaw, Andy <andy_liaw at 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]] > > > > > > ______________________________________________ > > > R-help at 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 at 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 at 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 >