From murdoch at stats.uwo.ca  Fri Sep  4 12:25:51 2009
From: murdoch at stats.uwo.ca (Duncan Murdoch)
Date: Fri, 04 Sep 2009 06:25:51 -0400
Subject: [Rd] Apparent bug in summaryBy (PR#13941)
In-Reply-To: <20090904024513.0B5F9282EF4F@mail.pubhealth.ku.dk>
References: <20090904024513.0B5F9282EF4F@mail.pubhealth.ku.dk>
Message-ID: <4AA0EB2F.8040804@stats.uwo.ca>

paterno at fnal.gov wrote:
> Full_Name: Marc Paterno
> Version: 2.9.2
> OS: Mac OS X 10.5.8
> Submission from: (NULL) (99.53.212.55)
>
>
> summaryBy() produces incorrect results when given some data  frames. Below is a
> transcript of a session showing the result, in a data frame with 2 observations
> of 2 variables.
>   

This looks like a bug in the doBy package (or something it uses), not a 
bug in R.  I've cc'd the maintainer of that package to let him know 
about it. 

By the way, an easier way to create that dataframe is simply

tmp <- data.frame(V1=c("c", "b"), V2=c(1,2))

Duncan Murdoch

> -------------------
> thomas:999 paterno$ R --vanilla
>
> R version 2.9.2 (2009-08-24)
> Copyright (C) 2009 The R Foundation for Statistical Computing
> ISBN 3-900051-07-0
>
> R is free software and comes with ABSOLUTELY NO WARRANTY.
> You are welcome to redistribute it under certain conditions.
> Type 'license()' or 'licence()' for distribution details.
>
>   Natural language support but running in an English locale
>
> R is a collaborative project with many contributors.
> Type 'contributors()' for more information and
> 'citation()' on how to cite R or R packages in publications.
>
> Type 'demo()' for some demos, 'help()' for on-line help, or
> 'help.start()' for an HTML browser interface to help.
> Type 'q()' to quit R.
>
>   
>> library(doBy)
>> tmp = read.table("moduledata_999_1.txt",header=FALSE)
>> str(tmp)
>>     
> 'data.frame':	2 obs. of  2 variables:
>  $ V1: Factor w/ 2 levels "b","c": 2 1
>  $ V2: num  1 2
>   
>> tmp
>>     
>   V1 V2
> 1  c  1
> 2  b  2
>   
>> summaryBy(V2~V1,tmp)
>>     
>   V1 V2.mean
> 1  b       1
> 2  c       2
>
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> https://stat.ethz.ch/mailman/listinfo/r-devel
>



[Rd] Apparent bug in summaryBy (PR#13941)
Duncan Murdoch