plot_ppc - KeyError: "['y'] var names are not present in dataset"

Hi, I’ve had troubles using plot_ppc in a project I’m working on, so I tried to reproduce it using the quickstart pystan example. This is the code I’m using:

schools_code = """
data {
  int<lower=0> J;
  real y[J];
  real<lower=0> sigma[J];
}

parameters {
  real mu;
  real<lower=0> tau;
  real theta[J];
}

model {
  mu ~ normal(0, 5);
  tau ~ cauchy(0, 5);
  theta ~ normal(mu, tau);
  y ~ normal(theta, sigma);
}
generated quantities {
    vector[J] log_lik;
    vector[J] y_hat;
    for (j in 1:J) {
        log_lik[j] = normal_lpdf(y[j] | theta[j], sigma[j]);
        y_hat[j] = normal_rng(theta[j], sigma[j]);
    }
}
"""

schools_dat = {'J': 8,
               'y': [28,  8, -3,  7, -1,  1, 18, 12],
               'sigma': [15, 10, 16, 11,  9, 11, 10, 18]}

sm = pystan.StanModel(model_code=schools_code, verbose=False)
fit = sm.sampling(data=schools_dat, iter=1000, chains=4)

data = az.from_pystan(posterior=fit,
                      posterior_predictive='y_hat',
                      observed_data=['y'],
                      log_likelihood='log_lik',
                      coords={'school': schools},
                      dims={'theta': ['school'], 'y': ['school'], 'log_lik': ['school'], 'y_hat': ['school'], 'theta_tilde': ['school']})

az.plot_ppc(data)

This raises:

KeyError: "['y'] var names are not present in dataset"

which is exactly the kind of error I got in my own project… I guess I’m doing something wrong, here, but I can’t figure out what it is.

Any help would be appreciated… thanks!

[amukh18]

Hello. I’d like to work on this issue!

[amukh18]

I understand. I will make the changes accordingly.