[R] Calculating Summaries for each level of a Categorical variable

Greg Snow Greg.Snow at imail.org
Mon Jun 28 19:23:33 CEST 2010

The problem is that tapply is expecting a vector for the first argument, your first argument is a list or data frame, so the length that it sees is the number of list elements (columns of the data frame).  You need to either pass a single vector, or use functions like aggregate or the plyr package to work on all the columns in a data frame.

Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of RaoulD
> Sent: Saturday, June 26, 2010 10:47 PM
> To: r-help at r-project.org
> Subject: Re: [R] Calculating Summaries for each level of a Categorical
> variable
> Hi Corey,
> Thanks so much for this. However, I get this error for tapply - "Error
> in
> tapply(RT, RT$R, fun=WA):
>   arguments must have same length". Any idea how to get around this?
> Thanks again,
> Raoul
> --
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> a-Categorical-variable-tp2269349p2269815.html
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