[R] : unusual combinations of categorical data

[Joshua Wiley]

Hi,

On Mon, Nov 8, 2010 at 2:25 PM, Alan Chalk <Alan.Chalk at gcc.rsagroup.com> wrote:
> Regarding unusual combinations of factors in categorical data.

where all variables are categorical?

> Are there any R packages that can be used to identify the outliers i.e.
> unusual combinations in categorical datasets ?

"outlier" or "unusual" tends to be rather variable, that is something
unusual in one data set may not be in another.  If you are dealing
with strictly categorical variables, I am not certain how you would
define an outlier.  The categories only have the meaning attached to
them, so it seems like they would only indicate outliers if you
decided that an entire category was an outlier (e.g., males, females,
half-man-half-ox).  If you have one continuous variable in mind by
different levels of a factor, then you could just use some simple
plots (e.g., ggplot() + geom_point() + facet_grid(factor ~ .) or
something similar).  You could also z-score the values by each factor
level and then extract zscores more extreme than +/- 3 or whatever
value you like.  It might be easier to give you feedback if you have a
more specific example.

Cheers,

Josh

>
> Thanks.
>
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-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/