extracting column at regular intervals starting from different columns

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..
This will start at 4 and then be recycled every succeeding 37th item:

offset1= 3; offset2 = 37
c( rep(FALSE, 3), TRUE, rep(FALSE, offset2-offset1-1) )

Observe:
 (1:100)[ c( rep(FALSE, 3), TRUE, rep(FALSE, offset2-offset1-1) ) ]
[1]  4 41 78
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
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______________________________________________
R-help at r-project.org mailing list
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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.
David Winsemius, MD
Alameda, CA, USA

extracting column at regular intervals starting from different columns

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