[R] output by(...)

[peter dalgaard]

On Mar 25, 2012, at 12:27 , Gabor Grothendieck wrote:

> 2012/3/25 Skála, Zdeněk (INCOMA GfK) <Zdenek.Skala at gfk.com>:
>> Dear all,
>> 
>> I have a question that is probably pretty stupid, so apologies in advance...
>> 
>> I do a simple
>> 
>>> mydata.tab <- by(my.data.frame, my.data.frame$category, colMeans)
>> 
>> ...works fine, but I need to output the results to some "flat" file (kind of table) to work with it in Excel etc.
>> 
>> So I am doing now
>> 
>>> capture.output(data.frame(unlist(mydata.tab)), file="mydata.txt")
>> 
>> ...and process the result in Excel.
>> Do you know a more pretty way to do this task? Perhaps something other than 'by()' to make a table of colMeans?
>> 
> 
> Try this:
> 
> do.call("rbind", by(iris[-5], iris[[5]], colMeans))
> 
> 

How about 

aggregate(iris[-5], iris[5], mean)

?

> 
> 
> -- 
> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
> tel: 1-877-GKX-GROUP
> email: ggrothendieck at gmail.com
> 
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-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com