[R] Re: [S] selecting arbitrary subsets from data frames

[Petr Pikal]

On 20 Nov 2001 at 17:55, Schwarz, Paul wrote:

> 
> I realize that this is a FAQ, and I have spent some time perusing 
the
> S-News archives trying to better understand the various 
approaches,
> but I would still appreciate advice from others on the list.
> 
> I have data stored as a data frame and individual rows are 
identified
> by plot number and by the individual within the plot.  Thus, 
there are
> several rows of data in the data frame corresponding to different
> individuals within each plot.  I would like to extract arbitrary
> subsets of plots (with all of the rows for each of the plot) from 
the
> data frame using a vector of plot numbers.  For example:
> 
> plotlist <- c(2,9,23,46,58)
> 
> So plotlist identifies the individual plot numbers but not the 
rows in
> the data frame.  How do I go about extracting all of the rows of 
data
> in the data frame for the plots contained in plotlist?  It seems 
like
> match() or is.element() are candidates for this task

Yes, something like

daf[is.element(daf$plotno,plotlist),]

suppose

daf is your data frame and plotno is column name with all plot 
numbers.

If you do not want whole row you can specify a vector of columns 
in front of ].

This works in R and I hope it will work in S+ too.
 
, but I must be
> missing the nuances of how to use these functions, and I would
> appreciate some insights.
> 
> Thanks for your time and patience.
> 
> -Paul
> 

Petr Pikal
petr.pikal at precheza.cz
p.pik at volny.cz


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