Hi,

I am trying to use mlogit in R to analyse a block design choice experiment
dataset. The 12 choice sets/cards have been randomly assigned to 3
different blocks and each respondent answers all sets from one block (i.e.
each respondent chooses from 4 choice sets). In total I have 2336 rows of
data from 292 respondents. The data looks like this (2 of the three
blocks):

ID  Sex Age Block   Card    Alt x1  x2  x3  x4  choice
1   0   65  1   4   1   0   1   1   1   0
1   0   65  1   4   2   0   0   0   0   1
1   0   65  1   7   1   1   0   1   0   0
1   0   65  1   7   2   1   2   0   1   1
1   0   65  1   10  1   1   1   0   1   1
1   0   65  1   10  2   0   2   1   0   0
1   0   65  1   12  1   1   2   0   0   0
1   0   65  1   12  2   1   0   1   1   1
2   1   35  2   2   1   0   2   0   0   0
2   1   35  2   2   2   0   0   1   1   1
2   1   35  2   8   1   0   1   0   1   1
2   1   35  2   8   2   0   1   1   0   0
2   1   35  2   9   1   0   1   0   1   0
2   1   35  2   9   2   1   1   0   0   1
2   1   35  2   11  1   0   0   1   0   0
2   1   35  2   11  2   1   2   0   1   1
I have tried the following codes to set the data for mlogit and run the
model:

T1m<-mlogit.data(T1,shape="long",choice="choice",alt.var="Alt")
m1=mlogit(choice~x1+x2+x3+x4|Age+Sex, data=T1m)
I am getting the following error:

Error in if (abs(x - oldx) < ftol) { : missing value where TRUE/FALSE
needed

I have gone through the data and found no missing values.

Please advice if the codes I have used are appropriate and what is going
wrong.

Thanks in advance,

abimoss

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