Mlogit function

I have a large dataset from my own survey. It is a stated preference survey where respondents had to choose between either a bicycle or a public transport commute. I have it saved as (these are columns:

Question (there were 15 possible questions. So just repeats 1..15 for a long time
ID: the ID of the respondent, 1 ... 186.
RES: Repondents saw a random 8 of the 15 questions, values are A, B or 0. A and B for bike or public transport and 0 for questions the respondent did not see
And then all the attributes.

It is in a long format.

Now when i try to do this in R I keep getting:

TM <-, choice = "choice", shape = "long", chid.var = "ID")
Error in FUN(X[[i]], ...) :
argument must be coercible to non-negative integer


TM <-, choice = "choice", shape = "long", chid.var = "ID", alt.var = "Question")
Error in dfidx::dfidx(data = data, dfa$idx, drop.index = dfa$drop.index, :
the two indexes don't define unique observations

Can anyone see what I am doing wrong? Its not letting me upload pictures unfortunately

Hi, welcome to the forum.

We probably need more information and some sample data . See

FAQ Asking Questions for some general information.

For easier readability please copy your code and paste it here between


A handy way to supply some sample data is the dput() function. In the case of a large dataset something like dput(head(mydata, 100)) should supply the data we need. Just do dput(mydata) where mydata is your data. Copy the output and paste it here between


hard to tell with out some sample data, but the error comes from dfidx::dfidx

z <- data[, c(posid1[1], posid2[1])]
if (nrow(z) != nrow(unique(z)))
stop("the two indexes don't define unique observations")