R help - May 2011 - Multinomial Logistical Model

On May 24, 2011; 11:06pm Belle wrote:
> Does anyone know how to run Multinomial logistical Model in R in order to
> get predicted probability?
Yes. I could stop there but you shouldn't. The author of the package
provides plenty of examples (and two good vignettes) showing you how to do
this. Suggest you do some work in that area. Look especially at how model
formulas are used/specified. This is at least one area where you have gone
wrong, as the error message clearly tells you.

Good luck.
Mark.

-----
Mark Difford (Ph.D.)
Research Associate
Botany Department
Nelson Mandela Metropolitan University
Port Elizabeth, South Africa
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I suggest a couple of courses before proceeding.  Multinomial logistic models
have special challenges.  And note that you have two nomenclature errors in
your note, which is usually a sign of not having taken the relevant
coursework.
Frank

Belle wrote:
> 
> Does anyone know how to run Multinomial logistical Model in R in order to
> get predicted probability?
> 
> The response is content (5 levels: 1, 2, 3, 4, 5)
> The covariance are:
> assignment - int (0, 1)
> dr0 - int (0, 1)
> dr1 - int (0, 1)
> yr_exp - num
> yr_exp_s - num
> ismgdr - int (0, 1)
> ismgyr_t_A - int (0, 1)
> pair - int (41 pairs: 1001, 1002, ...)
> 
> There is no random effect involved, all the variables are fixed. 
> 
> I have tried mlogit, but it does not work.
> 
> x <- SciContent
> x$content <- as.factor(x$content)
> mldata <- mlogit.data(x, varying=NULL, choice="content",
shape="wide")
> SciCt <- mlogit(mldata$content | mldata$assignment + mldata$dr0 +
> mldata$dr1 + mldata$yr_tch_exp + mldata$yr_tch_exp_s + mldata$ismgdr +
> mldata$ismgyr_t_A + mldata$pair)
> 
> Error: inherits(object, "formula") is not TRUE
> 

-----
Frank Harrell
Department of Biostatistics, Vanderbilt University
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