On Sep 18, 2012, at 10:21 AM, 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..
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_bo...@hotmail.com >> To: michael.weyla...@gmail.com >> Date: Tue, 18 Sep 2012 15:06:18 +0000 >> CC: r-help@r-project.org >> Subject: Re: [R] extracting column and regular interval in R >> >> >> thnkyou very much micheal. >> i worked!!! >> regards >> eliza >> >> >>> From: michael.weyla...@gmail.com >>> Date: Tue, 18 Sep 2012 15:58:31 +0100 >>> Subject: Re: [R] extracting column and regular interval in R >>> To: eliza_bo...@hotmail.com >>> CC: r-help@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_bo...@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@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@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@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 ______________________________________________ R-help@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.
