[R] factors

[Ista Zahn]

Hi Jonathan,

On Thu, May 5, 2011 at 6:28 PM, J <jonsleepy at gmail.com> wrote:
> Hi, I'm requesting you don't berate me for asking this question:
>
> I clearly don't have the gist of factors.
>
> I have two dataframes, A and B.
>
> Each of them has a column containing strings (they're labels).
>
> I want to, one-by-one in a loop, compare the particular string in an entry from dataframe A to an entry in B, to see if they're the same.

This is probably not the best way. Much easier to compare them all in one go.

>
> The problem, when posing the question:
> searchID1 <- A[['label']][i]
> possMatch1 <- B[['label']][j]
> searchID1 == possMatch1
>
> I get the error:
> Error in Ops.factor(searchID1, possMatch1) :
>  level sets of factors are different
>
> I presume this is because the set of possible values in the 'labels' columns, respectively in A and B, differ.  In my case, I'm not interested in this at all; I just want to compare individual entries from the two dataframes in a pair-wise fashion.
>
> Can I strip the "factors" associated with the entries?  Is there a better way?

Yes, you can "strip the factors" using as.character(). Alternatively,
you could use set the factor levels using factor() or levels. Either
way, I would just do

A$label == B$label

Instead of a loop.

Best,
Ista
>
> Jonathan
>
>
>        [[alternative HTML version deleted]]
>
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-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org