[R] Extracting only odd columns from a matrix

[rex.dwyer at syngenta.com]

Or, if X1 Y1 X2 Y2... are really your column names
m[, grep("X",colnames(m)) ]
or
m[, grepl("X",colnames(m)) ]

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Dimitris Rizopoulos
Sent: Wednesday, March 09, 2011 9:36 AM
To: Nixon, Matthew
Cc: r-help at R-project.org
Subject: Re: [R] Extracting only odd columns from a matrix

one way is using the seq(), e.g., say 'm' is your matrix, then try:

m[, seq(1, ncol(m), by = 2)]


I hope it helps.

Best,
Dimitris


On 3/9/2011 3:20 PM, Nixon, Matthew wrote:
> Hi,
>
> This might seem like a simple question but at the moment I am stuck for ideas. The columns of my matrix in which some data is stored are of this form:
>
> X1     Y1     X2     Y2     X3     Y3     ...     Xn     Yn
>
> with n~100. I would like to look at just the X values (i.e. odd column numbers). Is there an easy way to loop round extracting only these columns?
>
> Any help would be appreciated.
>
> Thank you.
> ______________________________________________
> 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
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>

--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014
Web: http://www.erasmusmc.nl/biostatistiek/

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