R help - Aug 2005 - reverse order of matrix rows

Quick question:  how can I reverse the order of the rows in a matrix?  
i.e. make the last row first and the first row last, etc.?

sapply(nrow(matrix):1, function(x) matrix[x,])



On Mon, 8 Aug 2005, Jake wrote:
> Quick question:  how can I reverse the order of the rows in a matrix?
> i.e. make the last row first and the first row last, etc.?
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>

Thanks to those who provided the one-liner answers!  They worked  
quite well.

I'm quite sure that 95% of the questions posted on this mailing list  
could be answered with a quick..."read the manual, stupid...", but  
I'm very grateful to those who take the time to write one-liners.   I  
know that I have been greatly helped by searching through archived  
questions from other people, which I'm sure to some R gurus must have  
seemed like stupid questions.  But in reality the Mailing List  
archives are an invaluable source of documentation, one that wouldn't  
exist if every question were met with a "go read the manual..."  
response.

--Jake

On Aug 8, 2005, at 5:35 PM, Berton Gunter wrote:

> Quick answer: Read "An Introduction to R" and learn about
indexing.
>
> -- Bert Gunter
> Genentech Non-Clinical Statistics
> South San Francisco, CA
>
> "The business of the statistician is to catalyze the scientific  
> learning
> process."  - George E. P. Box
>
>
>
>
>
>> -----Original Message-----
>> From: r-help-bounces at stat.math.ethz.ch
>> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Jake
>> Sent: Monday, August 08, 2005 2:58 PM
>> To: R-help at stat.math.ethz.ch
>> Subject: [R] reverse order of matrix rows
>>
>> Quick question:  how can I reverse the order of the rows in a
>> matrix?
>> i.e. make the last row first and the first row last, etc.?
>>
>> ______________________________________________
>> R-help at stat.math.ethz.ch mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide!
>> http://www.R-project.org/posting-guide.html
>>
>>
>>
>
>
>
>

How about simply 

	mat <- mat[ nrow(mat):1, ]

Regards, Adai



On Mon, 2005-08-08 at 19:44 -0400, Jean Eid wrote:
> sapply(nrow(matrix):1, function(x) matrix[x,])
> 
> 
> 
> On Mon, 8 Aug 2005, Jake wrote:
> 
> > Quick question:  how can I reverse the order of the rows in a matrix?
> > i.e. make the last row first and the first row last, etc.?
> >
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
> >
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>