[R] Question on Counting Factors

[David Winsemius]

On Apr 11, 2012, at 9:21 AM, Daniel Gabrieli wrote:

> Hi,
>
> I hope this is not too trivial, but I've had this recurring problem
> and I think there is super easy solution, just not sure what it is.
> Please see short example below.  I would like to get the frequency
> (counts) of all the variables in a single column (that is easy), but I
> would also like to return the value 0 for the absence of variables
> defined in another column.
>
> For example:
>
> animals =  
> matrix 
> (c('cat','tiger','cat','tiger','fish','fish','dog','dog'),ncol=2,
> byrow=F)
>
> animals = as.data.frame(animals)
>
> table(animals$V1)
>
> # Returns the count for the variables in the first column as
> cat tiger
>    2     2
>
> # But I would like to have table(animals$V1) return
>
> cat tiger  dog  fish
>    2     2    0      0
>
You need to add the missing levels to that factor.

 > levels(animals$V1) <-  
unique( c('cat','tiger','cat','tiger','fish','fish','dog','dog'))
 > table(animals$V1)

   cat tiger  fish   dog
     2     2     0     0


>
> Any help is much appreciated.
>
> Cheers,
>
> Dan
>
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David Winsemius, MD
West Hartford, CT