R help - Sep 2009 - Multinomial and Ordinal Logistic Regression - Probability calculation

Dear all,

I am new to R and would like to run a multinomial logistic regression on my
dataset (3 predictors for 1 dependent variables)

I have used the vglm function from the VGAM package and got some results. Using
the predict() function, I obtained the probability table I was looking for.
However, I would like to fully understand how the predict() function generates
the probabilities or in other terms, what is the equation that gives a
probability from the intercept and the coefficients from the regression.

I also ran an ordinal logistic regression using the lrm() functions from the
Design package and reached the same result without being able to explain the
probability calculation process.

Would anyone be able to help?

Thanks,

Olivier

	[[alternative HTML version deleted]]

I would add that I followed explanations from the following URL (UCLA):

http://www.ats.ucla.edu/stat/r/dae/mlogit.htm

I still don't know how the probabilities are generated from the coefficients
and intercepts...
Anybody ?

Thanks.



OLIVIER REGNIER-COUDERT (0509785) wrote:
> 
>  Dear all,
> 
> I am new to R and would like to run a multinomial logistic regression on
> my dataset (3 predictors for 1 dependent variables)
> 
> I have used the vglm function from the VGAM package and got some results.
> Using the predict() function, I obtained the probability table I was
> looking for. However, I would like to fully understand how the predict()
> function generates the probabilities or in other terms, what is the
> equation that gives a probability from the intercept and the coefficients
> from the regression.
> 
> I also ran an ordinal logistic regression using the lrm() functions from
> the Design package and reached the same result without being able to
> explain the probability calculation process.
> 
> Would anyone be able to help?
> 
> Thanks,
> 
> Olivier
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at 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.
> 
> 
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