[R] extracting column at regular intervals starting from different columns

[Clint Bowman]

Try:

x <- 1:444
start<-2
>x[c(rep(FALSE,start-1),TRUE, rep(FALSE, 36-start+1))]
# [1]   2  39  76 113 150 187 224 261 298 335 372 409
start<-30
x[c(rep(FALSE,start-1),TRUE, rep(FALSE, 36-start+1))]
# [1]  30  67 104 141 178 215 252 289 326 363 400 437
start<-37
x[c(rep(FALSE,start-1),TRUE, rep(FALSE, 36-start+1))]
# [1]  37  74 111 148 185 222 259 296 333 370 407 444



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On Tue, 18 Sep 2012, eliza botto wrote:

>
> Dear useRs,
> i had a matrix with 31 rows and 444 columns and i wanted to extract every 37th column of that matrix starting from 1. more precisely i wanted to select columns 1, 38,75, 112 and so on. then doing the same by starting from column number 2(2,39,76,113.......).
> i was advised to use
>> x[c(TRUE, rep(FALSE, 36)),]
> i works if it is start from first column but as i am very new to R i wanted to know what to do to make it work if i want to start column selection from column 2 and then from column 3 and so on.
> sorry for bothering you once again..
> regards
> eliza
>
>
>> From: eliza_botto at hotmail.com
>> To: michael.weylandt at gmail.com
>> Date: Tue, 18 Sep 2012 15:06:18 +0000
>> CC: r-help at r-project.org
>> Subject: Re: [R] extracting column and regular interval in R
>>
>>
>> thnkyou very much micheal.
>> i worked!!!
>> regards
>> eliza
>>
>>
>>> From: michael.weylandt at gmail.com
>>> Date: Tue, 18 Sep 2012 15:58:31 +0100
>>> Subject: Re: [R] extracting column and regular interval in R
>>> To: eliza_botto at hotmail.com
>>> CC: r-help at r-project.org
>>>
>>> x[c(TRUE, rep(FALSE, 36)),]
>>>
>>> and let recycling work its magic!
>>>
>>> To concretize:
>>>
>>> x <- 1:100
>>>
>>> x[c(TRUE, rep(FALSE, 4))]
>>>
>>> Cheers,
>>> Michael
>>>
>>> On Tue, Sep 18, 2012 at 3:55 PM, eliza botto <eliza_botto at hotmail.com> wrote:
>>>>
>>>> Dear R users,
>>>> i have a matrix with 31 rows and 444 columns and i want to extract every 37th column of that matrix starting from 1. more precisely i want to select columns 1, 38,75, 112 and so on. then doing the same by starting from column number 2(2,39,76,113.......).
>>>> i know that there is a manual way of doing it but i wanted to make it more quickly as i have fairly large data to dealth with.
>>>>
>>>> thanks in advance
>>>> eliza
>>>> [[alternative HTML version deleted]]
>>>>
>>>> ______________________________________________
>>>> R-help at r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>