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

[Costas Douvis]

Here's a simplified example

p<-1:80+rnorm(80)
dim(p)<-c(2,2,2,10)

We could say that the 4-d array p consists of 2*2*2 = 8 vectors of length
10. So what I'm asking for is a fast way to perform a linear fit to all
those vectors.

I'm sorry if I'm causing you to have a headache with all those dimensions :)
Kostas

> Well, could you provide a little bit more information regarding what
> you are trying to do (e.g., reproducible example).
>
> 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>; "Mark Leeds" <markleeds at verizon.net>;
> "Dimitris Rizopoulos" <dimitris.rizopoulos at med.kuleuven.be>
> Cc: "Chuck Cleland" <ccleland at optonline.net>
> Sent: Wednesday, April 09, 2008 3:44 PM
> Subject: Re: [R] apply lm() for all the columns of a matrix
>
>
>> 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
>>>> 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: cdouvis at geol.uoa.gr
>>>> tel: +30-210-8832048
>>>>
>>>> ______________________________________________
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>>>> 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
>>>
>>>
>>
>>
>
>
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>
>


-- 
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