From murdoch at stats.uwo.ca  Wed Feb  1 01:57:53 2006
From: murdoch at stats.uwo.ca (Duncan Murdoch)
Date: Tue, 31 Jan 2006 19:57:53 -0500
Subject: [Rd] [R] Help! What does this R command mean?
In-Reply-To: <971536df0601311355g7a4e9337iab7e356e533bcfee@mail.gmail.com>
References: <39B6DDB9048D0F4DAD42CB26AAFF0AFAFED79A@usctmx1106.merck.com>
	<971536df0601311355g7a4e9337iab7e356e533bcfee@mail.gmail.com>
Message-ID: <43E00791.7030506@stats.uwo.ca>

On 1/31/2006 4:55 PM, Gabor Grothendieck wrote:
> I think that a pointer to ?formula needs to be added to ?":"

Good suggestion; I'll do it.

Duncan Murdoch
> 
> 
> 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
>>
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel



[Rd] [R] Help! What does this R command mean?
Duncan Murdoch