[R] how to create a simple loop ?

[John Kane]

An alternative approach (clumsy  but probably not as clumsy as a loop) would be to create a sixth column as a factor and aggregate on that. Simple-minded example :
=======================================================
mydata  <- data.frame(matrix(rnorm(100),nrow=20))
mydata[,6] <- c(rep("a",5),rep("b",20-10),rep("c",5))
aggregate(mydata[,5], by=list(mydata[,6]), mean)

============================================================

Set all the unwanted values to X and subset on that before calculating.
--- On Sun, 12/27/09, Edouard Tallent <tallent_e at lycos.com> wrote:

> From: Edouard Tallent <tallent_e at lycos.com>
> Subject: [R] how to create a simple loop ?
> To: r-help at r-project.org
> Received: Sunday, December 27, 2009, 9:15 AM
> Hi everyone. And, Merry Xmas !
> I have a 5-row matrix called “data”. There are
> headers.
> it look like this :
> Row 1   Row2    Row3   
> Row4    Row5
> Line1     …     
>       …         
>   …            …
> Line2     …     
>       …         
>   …            …
> Line3     …     
>       …         
>   …            …
> …
> Line 1838         
>    …         
>   …           
> …            …
>  I want to calculate several simple arithmetic means for
> Row5, that is from Line173 to Line193, from Line434 to
> Line455, from Line699 to Line724, from Line955 to Line977
>  A simple way is to individually compute these means. The
> first one (Line173 to Line193) is then obtained by :
> >mean(data[173:193,5], na.rm = TRUE)
> That’s right ! But, I aim to automate this calculation by
> creating a loop.
> I tried many things, but I have been unsuccessful at using
> the ‘for’ loop function.
> Please, don’t explain things too hard as it is often the
> case that people wants to help but gets into too much
> sophistication.
> Someone can write that little code for this example ? Or
> suggest functions ?
> Thanks for your help.
> Cheers,
> Édouard.
> 
>     [[alternative(swapped) HTML version
> deleted]]
> 
> This is MIME Epilogue
> 
> 
> -----Inline Attachment Follows-----
> 
> ______________________________________________
> R-help at r-project.org
> mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained,
> reproducible code.
> 


      __________________________________________________________________
Looking for the perfect gift? Give the gift of Flickr! 

http://www.flickr.com/gift/