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Fit Multinomial Log-linear Models

Usage

multinom(formula, data=sys.parent(), weights, subset, na.action,
         contrasts=NULL, Hess=FALSE, summ=0, ...)

Arguments

formula a formula expression as for regression models, of the form response ~ predictors. The response should be a factor or a matrix with K columns, which will be interpreted as counts for each of K classes.

A log-linear model is fitted, with coefficients zero for the first class. An offset can be included: it should be a matrix with K columns if the response is a matrix with K columns or a factor with K > 2 classes, or a vector for a factor with 2 levels. See the documentation of formula for further details.

data an optional data frame in which to interpret the variables occurring in the formula.
weights optional case weights in fitting.
subset expression saying which subset of the rows of the data should be used in the fit. All observations are included by default.
na.action a function to filter missing data.
contrasts a list of contrasts to be used for some or all of the factors appearing as variables in the model formula.
Hess logical for whether the Hessian (the observed information matrix) should be returned.
summ integer; if non-zero, summarize by deleting duplicate rows and adjust weights. Methods 1 and 2 differ in speed (2 uses compiled C); method 3 also combines rows with the same X and different Y, which changes the baseline for the deviance.
... additional arguments for nnet.

Value

A nnet object with additional structure.
deviance the residual deviance.
edf the (effective) number of degrees of freedom used by the model
AIC the AIC for this fit.
Hessian (if Hess is true).

Examples

data(warpbreaks)
options(contrasts=c("contr.treatment", "contr.poly"))
multinom(breaks ~ wool, data=warpbreaks)

## S had -- VR data?
bwt.mu <- multinom(low ~ ., bwt)
bwt.mu
## Call:
## multinom(formula = low ~ ., data = bwt)
##
## Coefficients:
##  (Intercept)         age         lwt raceblack raceother
##     0.823477 -0.03724311 -0.01565475  1.192371 0.7406606
##      smoke      ptd        ht        ui       ftv1     ftv2+
##   0.7555234 1.343648 1.913213 0.6802007 -0.4363238 0.1789888
##
##
## Residual Deviance: 195.4755
## AIC: 217.4755