[R] Simple summary question

[Andrew Perrin]

Thanks! Worked great.

ap

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Andrew J Perrin - andrew_perrin at unc.edu - http://www.unc.edu/~aperrin
 Assistant Professor of Sociology, U of North Carolina, Chapel Hill
      269 Hamilton Hall, CB#3210, Chapel Hill, NC 27599-3210 USA


On 9 Jan 2002, A.J. Rossini wrote:

> >>>>> "AP" == Andrew Perrin <andrew_perrin at unc.edu> writes:
> 
>     AP> I'd like to get summary statistics (really just a mean would
>     AP> be fine) for a vector in a data frame, but split based on the
>     AP> value of another vector.  That is, I have a data frame
>     AP> (hcd.df) with variables datecat (which is always 1 or 2) and
>     AP> auth.sum (-8..+8).  I've used xtabs to get chi-square
>     AP> comparisons, but what I need now is a simple mean of auth.sum
>     AP> where datecat is 1 and another where datecat is 2. Thanks for
>     AP> any advice.
> 
> Something like :
> 
>         lapply(split(hcd.df$auth.sum,hcd.df$datecat),mean)
> 
> ?
> 
> 
> -- 
> A.J. Rossini				Rsrch. Asst. Prof. of Biostatistics
> U. of Washington Biostatistics		rossini at u.washington.edu	
> FHCRC/SCHARP/HIV Vaccine Trials Net	rossini at scharp.org
> -------------- http://software.biostat.washington.edu/ --------------
> FHCRC: M-W: 206-667-7025 (fax=4812)|Voicemail is pretty sketchy/use Email
> UW:   T-Th: 206-543-1044 (fax=3286)|Change last 4 digits of phone to FAX
> Rosen: (Mullins' Lab) Fridays, and I'm unreachable except by email.
> 

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