# Multinomial Logistic Regression

#### luisa021

##### New Member
Hi everybody!

I have a hmework I gotta do for my Econometrics course in college. I am testing the Dobson's ( An Introduction to generalized Linear m.) examples of multinomial regresion ( nominal in chapter 8 ).
First I obtained the 300 individual cases of the Car preferences problem , then I run it in Minitab, SPSS and R.

I was surprised when I saw that only Minitab got the results as the book! However neither R or SPSS got them! Actually the last two obtained the same result. The difference is in the interception estimator.

I tried and read a lot of manuals of SPSS in order to get the correct estimation, but nothing so far!

i went like this -->Analyze--> Regresion --> Multinomial logistic
There I put my answer as the grade of importance with reference customized in 1 ( no or less difference) , the ages and sex were my factors.

I don't know if you could help me ....I really need those results!

#### trinker

##### ggplot2orBust
I was surprised when I saw that only Minitab got the results as the book! However neither R or SPSS got them!
Now I'm wondering... Can you provide the R code you used to analyze the data (including the data set)? That would allow us to look it over and see if you perhaps missed something etc.

#### Dason

It could also be the way the program codes the dummy variables. I know R uses a "set first to 0" constraint on factors - I don't know how minitab or SPSS handle this but it might explain some discrepancy.

#### luisa021

##### New Member
Re: Multinomial Logistic Regression
here's my data set ............. https://rapidshare.com/files/1022309057/logistico.txt
I used the variables rpta, sex, ed1 and ed2. My reference level was 1 in rpta.
Perhaps I missed something in SPSS ' options, or wrote a bad R codification. Thanks a lot for the help!

R code:
Using package mlogit
data$rpta<-as.factor(data$rpta)