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rmlogit

Extracting Independent variables List from a mlogit object

I am using following package:

library(mlogit)

My data is prepared as follows

data(CollegeDistance, package="AER")
testdata <- CollegeDistance
testdata$Dist[testdata$distance<0.4] <- 1
testdata$Dist[testdata$distance<1 & testdata$distance>=0.4] <- 2
testdata$Dist[testdata$distance<2.5 & testdata$distance>=1] <- 3
testdata$Dist[testdata$distance>=2.5] <- 4

And here is my model

testmodel <- mlogit(as.formula(Dist ~ 1|urban + unemp + tuition|1), testdata, shape='wide', choice='Dist')

Now when I run following code the result is weird

as.character(attr(testmodel$formula, 'rhs')[[2]])

> as.character(attr(testmodel$formula, 'rhs')[[2]])
[1] "+"             "urban + unemp" "tuition"

What I expect is something like: 

chr [1:3] "urban" "unemp" "tuition"
Solution

  • You can use all.vars instead 

    all.vars(testmodel$formula) # return all the variables 
## "Dist"    "urban"   "unemp"   "tuition"
all.vars(testmodel$formula)[-1] # to remove the dependent variable
[1] "urban"   "unemp"   "tuition"

    and with the function you have used

    all.vars(attr(testmodel$formula, 'rhs')[[2]])
## [1] "urban"   "unemp"   "tuition"