[R] Output from the multinom-function
John Fox
jfox at mcmaster.ca
Wed Dec 12 14:36:39 CET 2001
Dear Mike,
I have some lecture notes on logistic regression, available at
<http://socserv.socsci.mcmaster.ca/jfox/Courses/soc740/chap15-overheads.pdf>,
which briefly describe the multinomial logit model; look in the section on
modeling polytomous data. You'd probably do well to read a text that covers
the subject; J. Long, Regression Models for Categorical and Limited
Dependent Variables (Sage, 1997) is quite accessible.
John
At 02:58 AM 12/12/2001 -0800, Hoodoo Gooroo wrote:
>Hello folks,
>
>Let me first apologize: I'm not a professional nor a
>mathematician, just an ordinary guy, fooling around
>with the excellent R-package. I know the basic
>principles behind statistics, but haven't read
>anything more advanced than the ordinary first
>probability and statistics courses.
>
>Enough disclaimers? Good! I was examining the
>multinom-function (in the nnet-package) the other day
>and run a couple of tests. This is part of an output I
>got.
>
>multinom(formula = result ~., data = info)
>
>Coefficients:
> (Intercept) PH WH
>1 -0.3974387 0.02201908 -0.0009618038
>2 2.5183566 -0.07076967 -0.0596189836
>
>The variable result I was trying to predict is a
>nominal variable, taking the values 0, 1 and 2. The
>independent variables are quite a few, some of them
>nominal, some not. I know about regression
>coefficients, intercepts, and all that jazz. I'm not
>sure, though, how I should use the coefficients and
>intercepts I got in the output. Why are there two
>different coefficients per variable? When should I use
>which? How should I interpret the output of the
>regression function? Should the output be rounded to
>the nearest integer, which would happen to be <=0, 1
>or >=2 -> I can decide which the prediction is? Or am
>I missing some fine points in this particular field of
>math I'm (admittedly somewhat blindfolded) messing
>around in?
>
>I'm grateful for any help, or any pointers to good
>sources on the web. I don't have any problems with
>reading theory - it's just that I don't have any
>theory to read!
>
>Thanks a lot in advance,
>
> Mike
-----------------------------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox
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