Hi all,
table() did the trick, and very efficiently, too! Thanks for the
advice,
Dave
On Thu, Jul 28, 2011 at 5:39 PM, David Winsemius <dwinsem...@comcast.net>wrote:
>
> On Jul 28, 2011, at 4:24 PM, David Warren wrote:
>
> Hi all,
>>
>> I'm working with a sizable dataset that I'd like to summarize, but I
>> can't find a tool or function that will do quite what I'd like.
>> Basically,
>> I'd like to summarize the data by fully crossing three variables and
>> getting
>> a count of the number of observations for every level of that 3-way
>> interaction. For example, if factors A, B, and C each have 3 levels (all
>> of
>> which were observed someplace in the dataset), I'd like to know how many
>> times A1, B1, and C1 co-occurred in the dataset. Functions like aggregate
>> and summaryBy do a decent job when I sum a vector of ones of the same
>> length
>> as the original dataset, but I'm getting stuck on the fact that neither
>> will
>> return 0-count combinations of the three variables in question.
>>
>
> I think that may depend on what functions and arguments you use.
>
>
> I understand that this is a desirable outcome (if A1, B1, C2 didn't
>> occur, it
>> shouldn't be counted and isn't), but I need to know both when these
>> combinations of factor did and did not occur. I'm stuck on this one, and
>> would really appreciate any help. Thanks in advance!
>>
>
> ?xtabs
>
>
>
>> Dave Warren
>>
>> PS A functional solution would be best; the original dataset contains
>> about
>> 2.3 million observations, so any looping is going to be very slow.
>>
>
> In general tabulations like these are very efficient.
>
> --
>
> David Winsemius, MD
> West Hartford, CT
>
>
--
Post-doctoral Fellow
Neurology Department
University of Iowa Hospitals and Clinics
davideugenewar...@gmail.com
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