I appreciate all the help.  The trouble is that in my real data set each
group does not always have an observation that choose each response. This
results in some of the "rows" returned from prop.table() to be shorter than
others so I get:

Warning message:
In function (..., deparse.level = 1)  :
  number of columns of result is not a multiple of vector length (arg 8)

Is there a way to tell rbind() or do.call() to treat missing values as zero
or make prop.table() include the zero proportions?



On Fri, May 23, 2008 at 1:59 PM, Phil Spector <spector@stat.berkeley.edu>
wrote:

> EG -
>    Thanks for the reproducible example!
>
>    When I run your code, and check the class of the result from tapply(), I
> see that it is an
> "array", and using dim(), I see it's an array
> of length 500.  How big is each element?
>
>  table(sapply(res,length))
>>
>
>  5
> 500
>
> So each piece is the same length.  That means we could
> make a 500x5 matrix as follows:
>
> do.call(rbind,res)
>                                       - Phil Spector
>                                         Statistical Computing Facility
>                                         Department of Statistics
>                                         UC Berkeley
>                                         spector@stat.berkeley.edu
>
>
>
>
>
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>

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