[R] Using data frame col names and variables

[David Winsemius]

On Jul 30, 2010, at 2:12 PM, Cadmium 2 wrote:

> Hi to you all!
>
> I'm new to R and to this mailing list, so do please excuse me if my  
> question
> sounds stupid.
>
> Currently I'm working with a data frame called "results".
>
> In each column of "results" I have a set of results for different
> experiments  (all results are numerical) realized in different  
> dates, so
> that each row corresponds to a day.
>
> To make it clear when displaying the results, I gave names to the  
> columns
> with the names of the experiments realized. I also gave names to the  
> rows
> based on the day the experiments where realized.
>
> My problem now is that I'm trying to separate this experiments based  
> on a
> criteria that is not important for the moment. What I want to be  
> able to do
> is, given an experiment name, obtain the time series of the results  
> of that
> experiment.
>
> I know I can do this by typing
>
> results$nameoftheexperiment
>
> But what if I have a variable "name" which contains the experiment's  
> name?
>
> Doing the following
>
> results$name
>
> doesn't work, as expected, since there is no column with name name.

Try:

results[ , name]

And read the the help page for ?Extract. The $ formalism does not  
evaluate its argument whereas the [ function does.

-- 
David.


>
> Any help would be appreciated.
>
> Thank you very much!
>
> 	[[alternative HTML version deleted]]
>
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David Winsemius, MD
West Hartford, CT