Factors and Multinomial Logistic Regression
On May 1, 2013, at 15:48 , Lorenzo Isella wrote:
Dear All, I am trying to reproduce the example that I found online here http://bit.ly/11VG4ha However, when I run my script (pasted at the end of the email), I notice that there is a factor 2 between the values for the coefficients for the categorical variable female calculated by my script and in the online example. Any idea about where this difference comes from? Besides, how can I extract the p-values for the calculated coefficients of my model and for the relative risk ratios? Best Regards
(A) The example doesn't run for me. library(ares) is not available on current R versions, but even where it is available, it doesn't provide a multinom() function? (B) If I insert library(nnet), to get a multinom(), I get exactly the same result as Stata does! Did you by any chance diddle with options(contrasts=...)? -pd
Lorenzo ########################################################################### library(ares) library(foreign) ## See the Stata example at http://bit.ly/11VG4ha mydata <- read.dta("http://www.ats.ucla.edu/stat/data/hsb2.dta") ## IMPORTANT: redefine the base line!!! mydata$ses2 <- relevel(mydata$ses, ref = "middle") mymodel <- multinom(ses2 ~ science+ socst+ female, data=mydata) print(summary(mymodel)) print("The relative risk ratio (RRR) is, ") print(exp(coef(mymodel)))
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