Do standard functions from arviz use samples from every chain, or just one chain?

Just a quick question. If you sample multiple chains from your model, do standard functions from arviz like az.plot_posterior (used to plot posterior), az.hdi (used to construct highest density interval) use samples from all the chains, or just one of the chains (for example the first)?

I did a quick sanity check where I sampled two chains of very few samples (like 2 chains of 10 samples) and az.plot_posterior plotted a bimodal distribution from that, so it looks like the arviz functions are using all the chains, but I thought I’d ask just to double check.


I think so. Some even throw warnings if there’s just one chain, e.g. az.summary().


I can confirm that ArviZ uses data from all chains in all its functions