[R] Fitting model with response and day bias

[Bart Joosen]

Bernardo,

thanks for your solution, I was short in time last weeks, but I tried it and 
it works fine.
I'll post it to the list, as it may help other people too.

Regards


Bart

----- Original Message ----- 
From: "Bernardo Rangel Tura" <tura at centroin.com.br>
To: "Bart Joosen" <Bartjoosen at hotmail.com>
Sent: Wednesday, May 30, 2007 8:36 PM
Subject: Re: [R] Fitting model with response and day bias


> On Wed, 2007-05-30 at 17:20 +0200, Bart Joosen wrote:
>> Hello,
>>
>> you are right about lm(I(y/time)~x1+x2), but what I would like to do is:
>> lm(y~(x1+x2)*time), where x1 and x2 should have coefficients, but time 
>> not.
>> Time is just used as a multiplier and should not have a coefficient.
>> But I don't know if its possible.
>>
>> The reason why time is not in my code is that it's simplified to make it 
>> a
>> bit understandable.
>>
>>
>> Thanks anyway
>>
>> Bart
>
> Bart,
>
> If I understand you problem, you have a dataset with 4 variables (y, x1,
> x2 and time) and you need fit them model:
>
> y = A+B*(x1*time)+C*(x2*time)+error
>
> and use command: lm(y~(x1+x2)*time).
>
> I think the comand is: lm(y~I(x1*time)+I(x2*time))
>
> I sugest try this ...
>
> I hope this help you ...
>
> If is solve your problem put solution in list to help other people
> -- 
> Bernardo Rangel Tura, M.D, PhD
> National Institute of Cardiolgy
> Rio de Janeiro - Brasil
>
>