# [R] apply lm() for all the columns of a matrix

Costas Douvis cdouvis at geol.uoa.gr
Wed Apr 9 15:44:08 CEST 2008

```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" <cdouvis at geol.uoa.gr>
> To: <r-help at 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
>> 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: cdouvis at geol.uoa.gr
>> tel: +30-210-8832048
>>
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>
>
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>

```