Thank you all very much for replying. Of course you are absolutely right but unfortunately I really deal with the case of a 4-d matrix so what you said does not apply. I should have specified but being a new R user I hadn't realized the difference between a matrix and an array.
So please tell me if you know a fast way (not using a loop) to perform a linear fit on all the vectors of the 4-th dimension of a 4-d array. Thanks again Kostas > If you have the same design matrix then you can specify a matrix of > responses in lm(), e.g., > > Y <- matrix(rnorm(100*10), 100, 10) > x <- rnorm(100) > > fit <- lm(Y ~ x) > fit > summary(fit) > > > I hope it helps. > > Best, > Dimitris > > ---- > Dimitris Rizopoulos > 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: "Costas Douvis" <[EMAIL PROTECTED]> > To: <r-help@r-project.org> > Sent: Wednesday, April 09, 2008 12:55 PM > Subject: [R] apply lm() for all the columns of a matrix > > >> Hi all, >> >> My question is not really urgent. I can write a loop and solve the >> problem. But I know that I'll be in a similar situation many more >> times so >> it would be useful to find out the answer >> >> Is there a fast way to perform linear fit to all the columns of a >> matrix? >> (or in the one dimension of a multi-dimensional array.) I'm talking >> about >> many single linear fits, not about a multiple fit. I thought that a >> combination of apply and lm would do it but I can't make it work >> >> Thank you >> Kostas >> >> >> -- >> Kostas Douvis >> PhD Student >> University of Athens - Department of Geography and Climatology >> Academy of Athens - Research Centre for Atmospheric Physics and >> Climatology >> email: [EMAIL PROTECTED] >> tel: +30-210-8832048 >> >> ______________________________________________ >> R-help@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. >> > > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm > > ______________________________________________ R-help@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.