R help - Jun 2007 - how to extract the maximum from a matrix?

Dear UseRs,
I have a very simple question. I have a big matrix (say x) including 
probabilities (values in (0,1)).
I have to store in a list the names of the row and the column where max(x) 
is located. How can I proceed?

Thanks in advance for your assistance!

mirko

look at the `arr.ind' argument of ?which(), e.g.,

x <- matrix(rnorm(9), 3, 3)
x
which(x == max(x), arr.ind = TRUE)


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "mirko sanpietrucci" <mirko.sanpietrucci at email.it>
To: <r-help at stat.math.ethz.ch>
Sent: Friday, June 01, 2007 11:09 AM
Subject: [R] how to extract the maximum from a matrix?

> Dear UseRs,
> I have a very simple question. I have a big matrix (say x) including
> probabilities (values in (0,1)).
> I have to store in a list the names of the row and the column where 
> max(x)
> is located. How can I proceed?
>
> Thanks in advance for your assistance!
>
> mirko
>
> ______________________________________________
> 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
> and provide commented, minimal, self-contained, reproducible code.
> 

Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm

Hi

If you have tried to go through help pages of max you could find out which 
function, which can tell you position of your maximum.

which(x==max(x), arr.ind=T)

Regards

Petr Pikal
petr.pikal at precheza.cz

r-help-bounces at stat.math.ethz.ch napsal dne 01.06.2007 11:09:09:
> Dear UseRs,
> I have a very simple question. I have a big matrix (say x) including 
> probabilities (values in (0,1)).
> I have to store in a list the names of the row and the column where 
max(x) 
> is located. How can I proceed?
> 
> Thanks in advance for your assistance!
> 
> mirko
> 
> ______________________________________________
> 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
> and provide commented, minimal, self-contained, reproducible code.