[R] Difficulties with dataframe filter using elements from an array created using a for loop or seq()

[Prof Brian Ripley]

FAQ Q7.31

On Tue, 20 Feb 2007, Todd A. Johnson wrote:

> Hi All-
>
> This seems like such a pathetic problem to be posting about, but I have no
> idea why this testcase does not work.  I have tried this using R 2.4.1,
> 2.4.0, 2.3.0, and 2.0.0 on several different computers (Mac OS 10.4.8,
> Windows XP, Linux).  Below the signature, you will find my test case R code.
>
> My point in this folly is to take a dataframe of 300,000 rows, create a
> filter based on two of the rows, and count the number of rows in the
> filtered and unfiltered dataframe.  One column in the filter only has the
> numbers 0.05, 0.15, 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85, 0.95, so I
> thought that I could just iterate in a for loop and get the job done. Just
> the simple single column filter case is presented here. Obviously, there are
> only ten numbers, so the "manual" method is easy, but I would like to have a
> more flexible program. (Plus it worries me if the simple things don't do
> what I expect... :-) )
>
>> From the output, you can see that the loop using the "handmadevector" that
> creates a filter and counts the elements, correctly finds one match for each
> element in the vector, but the seq() and for loop produced vectors each give
> a mixture of true and false matches.
>
> Can anyone tell me why the "loopvector" and "seqvector" do not provide the
> same output as the "handmadevector".
>
>
> Thank you for your assistance!
>
> Todd
>
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
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