How to calculate the mean of the specified chains and draws

[LevCarlo]

trace = az.from_netcdf(trace_filepath)
selected_posterior = trace.posterior.sel(chain=selected_chains, draw=selected_draws)
selected_posterior[list(trace.posterior.data_vars)[0]].mean(("chain", "draw"))
why does the code get stuck when applying mean method to selected_posterior?

[ahartikainen]

What do you mean by stuck?

What do you get with .mean(["chain", "draw"])?

[LevCarlo]

What do you mean by stuck?

What do you get with .mean(["chain", "draw"])?

No output after ~20 minutes running. trace.posterior.mean(("chain", "draw")) works well, but not for selected_posterior.

[ahartikainen]

Before calling the mean make sure selected posterior looks the way you expect it to look.

Then take the first data_var and check again. Then call mean.

Also make sure you want to use .sel and not .isel.

Are you certain that selected draw and selected chain are good?

[ahartikainen]

Can you run this example normally?

import arviz as az
data = az.load_arviz_data("centered_eight")
selected_posterior = data.posterior.sel(chain=[1,2], draw=list(range(422)))
print("selected_posterior:", selected_posterior[list(data.posterior.data_vars)[0]])
print("\nmean:", selected_posterior[list(data.posterior.data_vars)[0]].mean(("chain", "draw")))