R help - Dec 2003 - iterative proportional fitting

Dear all,

I wonder if there are some function or package in R which can do the 
iterative proportional fitting.

In the exponential model 
f(y1,...yn)=exp(a'yi+b'(yi*yj)+.....+c'(y1*...*yn)+constance),

instead of the canonical parameters, I use maginal probability instead of a 
and log odds ratio instead of b. and for the order higher than 3, I use the 
canonical way or even assume them to be 0.

It is good if there is direct function or package in R to do the job, which 
will save a lot of time of me. Thank you!

Rgs,

Zhen

Have you considered fitting on the log scale?  It's not clear to 
me what problem you are trying to solve, but the following will estimate 
parameters in a model that looks to me like what you are describing:  

      lm(z ~ (y1+y2+...+yn)^n, ...)

      hope this helps. 
      spencer

Zhen Pang wrote:
> Dear all,
>
> I wonder if there are some function or package in R which can do the 
> iterative proportional fitting.
>
> In the exponential model 
> f(y1,...yn)=exp(a'yi+b'(yi*yj)+.....+c'(y1*...*yn)+constance),
>
> instead of the canonical parameters, I use maginal probability instead 
> of a and log odds ratio instead of b. and for the order higher than 3, 
> I use the canonical way or even assume them to be 0.
>
> It is good if there is direct function or package in R to do the job, 
> which will save a lot of time of me. Thank you!
>
> Rgs,
>
> Zhen