extract().to_dataframe() from a StanFit4Model does not work on pystan 2.18

Question

I have estimated a model using pystan:

import pystan

stan_model = pystan.StanModel('stan_codes/stan_code_1.stan')
samples = stan_model.sampling(data = sdata, iter = 10, chains = 1, seed = 42)
model_results = {'mdata' : model_data, 'sdata': sdata, 'samples' : samples, 'model': stan_model}

Later I want to extract the "stuff" from the samples into a dataframe format. I am using

mdata, sdata, samples, model = [x for x in model_results.values()]
samples.extract().to_dataframe()

But I am getting an error:

 AttributeError: 'collections.OrderedDict' object has no attribute 'to_dataframe'

According to the documentation the samples.extract() should have an attribute to_dataframe(), right ? Am i doing something wrong here ? I am using pystan version 2.18.0.0

Answer 1

Have you tried the extraction to DataFrame direct from the fit object

Something like ...

stan_model = pystan.StanModel('stan_codes/stan_code_1.stan')
samples = stan_model.sampling(data = sdata, iter = 10, chains = 1, seed = 42)
chains = samples.to_dataframe('parameter name')