[R] Question about predict.multinom()

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From: Giovanni Petris (GPetris@uark.edu)
Date: Wed 12 May 2004 - 06:31:53 EST


Message-id: <200405112031.i4BKVrqi005073@definetti.uark.edu>


Hello,

This is the fitted model:

> fit
Call:
multinom(formula = resp ~ pred$cls + pred$smoke)

Coefficients:
             (Intercept) pred$cls2 pred$cls3 pred$cls4 pred$cls5 pred$smoke2 pred$smoke3
Proteinuria -1.140520 0.1616644 0.05554898 -0.01584927 0.02574805 -0.4057245 -0.2898425
Hypertension -2.691215 -0.3699690 -0.22582107 0.01615898 0.26318005 0.1239051 0.2413282
Both -2.285950 -0.4473108 -0.16212932 -0.10477158 0.01272335 -0.4852405 -0.6290152

Residual Deviance: 22809.76
AIC: 22851.76

... and these, to my understanding, should be the estimated category
probabilities for a subject in the first `cls' category and 3rd
`smoke' category:

> predict(fit, newdata=data.frame(cls=factor("1",levels=levels(pred$cls)),
+ smoke=factor("3",levels=levels(pred$smoke))), type="probs")
     Neither Proteinuria Hypertension Both
   0.6715336 0.7394394 0.7247787 0.6722327

Why I am not getting probabilities? Could somebody tell me what I am
missing?

Thank you in advance,
Giovanni

-- 

__________________________________________________ [ ] [ Giovanni Petris GPetris@uark.edu ] [ Department of Mathematical Sciences ] [ University of Arkansas - Fayetteville, AR 72701 ] [ Ph: (479) 575-6324, 575-8630 (fax) ] [ http://definetti.uark.edu/~gpetris/ ] [__________________________________________________]

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