Re: Selecting every other line from a data frame

[Tony Plate <tplate@blackmesacapital.com>]

In general, it's wise to avoid the idiom 1:n, because when n is zero, 
this generates the vector c(1,0), which is rarely (ever?) what you want. 
 Instead use seq(len=n).
The R-faq has some pointers to some good books on S-PLUS & R.  Find it 
at www.r-project.org.
-- Tony Plate

Khan, Sohail wrote:
> Thanks Tony and Chritos. Its great!!
>
> Could you recommend a good S book to learn this sort of stuff?
>
> -Sohail
>
> -----Original Message-----
> From: s-news-owner@lists.biostat.wustl.edu
> [mailto:s-news-owner@lists.biostat.wustl.edu]On Behalf Of Christos
> Hatzis
> Sent: Friday, April 21, 2006 11:53 AM
> To: christos@nuverabio.com; Khan, Sohail; s-news@lists.biostat.wustl.edu
> Subject: Re: [S] Selecting every other line from a data frame
>
>
> Sorry it should be: 
>
> my.df[ (1:nrow(my.df)) %% 2 == 0, ]
>
> -----Original Message-----
> From: s-news-owner@lists.biostat.wustl.edu
> [mailto:s-news-owner@lists.biostat.wustl.edu] On Behalf Of Christos Hatzis
> Sent: Friday, April 21, 2006 11:51 AM
> To: 'Khan, Sohail'; s-news@lists.biostat.wustl.edu
> Subject: Re: [S] Selecting every other line from a data frame
>
> You can try the following:
>
> my.df[ nrow(my.df) %% 2 == 0, ]
>
> for selecting even lines or == 1 for odd lines.
>
> -Christos 
>
> -----Original Message-----
> From: s-news-owner@lists.biostat.wustl.edu
> [mailto:s-news-owner@lists.biostat.wustl.edu] On Behalf Of Khan, Sohail
> Sent: Friday, April 21, 2006 11:46 AM
> To: s-news@lists.biostat.wustl.edu
> Subject: [S] Selecting every other line from a data frame
>
> Dear All,
>
> I have a large data frame, from which I want to only select every other line
> or odd lines.
> How can I do this?  Thanks.
>
>
> Sohail Khan
> Scientific Programmer
> COLD SPRING HARBOR LABORATORY
> Genome Research Center
> 500 Sunnyside Boulevard
> Woodbury, NY 11797
> (516)422-4076
>
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