I am trying to implement an ordered-probit model described in a (draft) paper by Liddell & Kruschke (Paper and its source code http://osf.io/53ce9)
The paper implements the model in R/JAGS and is not terribly complex but I have difficulties getting it to work in PyMC3. https://github.com/JWarmenhoven/DBDA-python/blob/master/Notebooks/Ordinal%20Model_Kruschke_Liddell.ipynb
Because of the custom Theano Operation to calculate the thresholded cumulative normal probabilities I cannot sample using NUTS. The Metropolis sampler sampler does not converge.
Likelihood: I am not sure whether I use the right distribution and feeding it the correct data. The JAGS model seems to use counts for respective ordinal value and not percentages.