# \#arviz

**URL:** https://discourse.pymc.io/tag/arviz/76.md

[Latest](https://discourse.pymc.io/latest.md) · [Categories](https://discourse.pymc.io/categories.md) · [Tags](https://discourse.pymc.io/tags.md)

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## [Arviz Issues following Tutorials](https://discourse.pymc.io/t/arviz-issues-following-tutorials/17874)

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**Author:** [@Pegguins](https://discourse.pymc.io/u/Pegguins)\
**Replies:** 2\
**Last updated:** [July 21, 2026, 8:34am UTC](https://discourse.pymc.io/t/arviz-issues-following-tutorials/17874 "2026-07-21T08:34:07Z")

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Hi. I’ve been trying to follow along the data containers tutorial: Using Data Containers — PyMC example gallery To try understand the data structures and model specification better. (I’m only used to using the R style …

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## [ArviZ 1.0 release](https://discourse.pymc.io/t/arviz-1-0-release/17692)

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**Author:** [@aloctavodia](https://discourse.pymc.io/u/aloctavodia)\
**Replies:** 5\
**Last updated:** [April 23, 2026, 6:46am UTC](https://discourse.pymc.io/t/arviz-1-0-release/17692 "2026-04-23T06:46:32Z")

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We have been refactoring ArviZ to improve modularity and flexibility, while preserving a user-friendly interface that works well with minimal input. Following this effort, we have recently released ArviZ 1.0. Modular st…

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## [New Contributor to PyMC](https://discourse.pymc.io/t/new-contributor-to-pymc/17497)

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**Author:** [@Moazzam-SK](https://discourse.pymc.io/u/Moazzam-SK)\
**Replies:** 2\
**Last updated:** [December 26, 2025, 7:03pm UTC](https://discourse.pymc.io/t/new-contributor-to-pymc/17497 "2025-12-26T19:03:35Z")

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Hello all, I’m Moazzam Shahzazd, a sophomore studying Computer Science, and I’m trying to contribute to PyMC. I’ve already opened a PR (#7979). In summary, what began as an attempt to silence a UserWarning evolved into r…

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## [How to display a single deterministic output of a Bayesian regression model using ArviZ](https://discourse.pymc.io/t/how-to-display-a-single-deterministic-output-of-a-bayesian-regression-model-using-arviz/17361)

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**Author:** [@serdar](https://discourse.pymc.io/u/serdar)\
**Replies:** 7\
**Last updated:** [October 6, 2025, 5:53am UTC](https://discourse.pymc.io/t/how-to-display-a-single-deterministic-output-of-a-bayesian-regression-model-using-arviz/17361 "2025-10-06T05:53:53Z")

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Let’s say I have a dataset of X and Y with 100 observations from each. I developed a Bayesian simple linear regression model from X to Y, using PyMC, like this: Y = Alpha + Beta \* X + Epsilon As you appreciate, there w…

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## [Working with Multi-index Coords](https://discourse.pymc.io/t/working-with-multi-index-coords/16113)

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**Author:** [@dreycenfoiles](https://discourse.pymc.io/u/dreycenfoiles)\
**Replies:** 12\
**Last updated:** [September 8, 2025, 8:48pm UTC](https://discourse.pymc.io/t/working-with-multi-index-coords/16113 "2025-09-08T20:48:36Z")

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Hello, I’ve got an ArviZ and PyMC combo question. I’ve been working with some uneven, long, data that I’m managing with multi-indexes. This workflow works pretty well except PyMC models can’t accept multi-indexes in the…

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## [How to save trace in between sampling and then resume sampling later on?](https://discourse.pymc.io/t/how-to-save-trace-in-between-sampling-and-then-resume-sampling-later-on/16785)

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**Author:** [@Aravind27](https://discourse.pymc.io/u/Aravind27)\
**Replies:** 2\
**Last updated:** [July 10, 2025, 4:36am UTC](https://discourse.pymc.io/t/how-to-save-trace-in-between-sampling-and-then-resume-sampling-later-on/16785 "2025-07-10T04:36:41Z")

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Hello everyone, I would like to save the trace every n samples or so. Is there a way to do this in pymc? Specifically, I would like to do something like the following pseudo code: with pm.Model() as model: ## priors…

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## [Workarounds for \`arviz\` no longer supporting \`MultiTrace\`?](https://discourse.pymc.io/t/workarounds-for-arviz-no-longer-supporting-multitrace/16362)

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**Author:** [@thaidollas](https://discourse.pymc.io/u/thaidollas)\
**Replies:** 6\
**Last updated:** [July 9, 2025, 10:01pm UTC](https://discourse.pymc.io/t/workarounds-for-arviz-no-longer-supporting-multitrace/16362 "2025-07-09T22:01:34Z")

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I recently updated from pymc3 to pymc v5. I’m also using arviz version 0.17.1. I have a model with a large number of parameters and due to memory considerations, I’m trying to stick with MultiTrace instead of InferenceDa…

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## [Variables not appearing in pm.sample\_posterior\_predictive](https://discourse.pymc.io/t/variables-not-appearing-in-pm-sample-posterior-predictive/16344)

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**Author:** [@Wesley\_Young](https://discourse.pymc.io/u/Wesley_Young)\
**Replies:** 1\
**Last updated:** [July 9, 2025, 9:46pm UTC](https://discourse.pymc.io/t/variables-not-appearing-in-pm-sample-posterior-predictive/16344 "2025-07-09T21:46:07Z")

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Using the model below, I expect to be able to use az.plot\_ppc to be able to see if the models is able to predict values for travel\_time\_obs. Yet when I go to run that command, I am told that other var names are not prese…

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## [Plot\_kde in 2D with hdi contours only](https://discourse.pymc.io/t/plot-kde-in-2d-with-hdi-contours-only/16265)

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**Author:** [@Pawel](https://discourse.pymc.io/u/Pawel)\
**Replies:** 2\
**Last updated:** [July 9, 2025, 9:40pm UTC](https://discourse.pymc.io/t/plot-kde-in-2d-with-hdi-contours-only/16265 "2025-07-09T21:40:58Z")

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Hi! I want to use the az.plot\_kde for 2D data, but I’d like to simplify the default aesthetics, so that all that is plotted are contours for selected hdi\_probs. Could You please tell me if and how could I do that? Also, …

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## [How to plot a posterior check of a bivariate variable](https://discourse.pymc.io/t/how-to-plot-a-posterior-check-of-a-bivariate-variable/17078)

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**Author:** [@alexcom](https://discourse.pymc.io/u/alexcom)\
**Replies:** 2\
**Last updated:** [June 9, 2025, 11:30pm UTC](https://discourse.pymc.io/t/how-to-plot-a-posterior-check-of-a-bivariate-variable/17078 "2025-06-09T23:30:43Z")

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@pymc-bot Hi, I’m just trying to plot the posterior of a bivariate poisson with coordiantes "dim\_0" and "dim\_1". The dim\_1 is the match and the dim\_0 is the amout of goals scored by local and away team of that match. …

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## [Cannot plot ppc for specific sub\_groups](https://discourse.pymc.io/t/cannot-plot-ppc-for-specific-sub-groups/16954)

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**Author:** [@Kristoffer\_Drejer](https://discourse.pymc.io/u/Kristoffer_Drejer)\
**Replies:** 3\
**Last updated:** [June 7, 2025, 3:40pm UTC](https://discourse.pymc.io/t/cannot-plot-ppc-for-specific-sub-groups/16954 "2025-06-07T15:40:30Z")

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I have this model which seems to perform fairly well, i’d like to plot\_ppc for specific sub\_groups though, which i can’t figure out how to do using az.plot\_ppc. How do I create a ppc plot for each sub\_group? # Create ma…

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## [4d parameter array from PyJAGS into ArviZ?](https://discourse.pymc.io/t/4d-parameter-array-from-pyjags-into-arviz/16967)

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**Author:** [@cjp](https://discourse.pymc.io/u/cjp)\
**Replies:** 1\
**Last updated:** [May 1, 2025, 9:19pm UTC](https://discourse.pymc.io/t/4d-parameter-array-from-pyjags-into-arviz/16967 "2025-05-01T21:19:34Z")

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Hi all, Let me know if there is a better place to post this. I’m trying to convert sample output from PyJAGS into an ArviZ InferenceData object using arviz.from\_pyjags(), but this fails with ValueError: too many values…

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## [Generalized LV: missing 1 required positional argument using pymc.ode.DifferentialEquation](https://discourse.pymc.io/t/generalized-lv-missing-1-required-positional-argument-using-pymc-ode-differentialequation/16756)

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**Author:** [@snjie209](https://discourse.pymc.io/u/snjie209)\
**Replies:** 0\
**Last updated:** [March 25, 2025, 5:12pm UTC](https://discourse.pymc.io/t/generalized-lv-missing-1-required-positional-argument-using-pymc-ode-differentialequation/16756 "2025-03-25T17:12:41Z")

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Hi team, I am trying to train a generalized Lotka Volterra using pymc. I have a 500 x 30 dataset where there are 500 data points and 30 time series. # Run only in the beginning !pip install --force-reinstall numpy==1.…

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## [Unexpected behavior with arviz.plot\_hdi() with categorical x](https://discourse.pymc.io/t/unexpected-behavior-with-arviz-plot-hdi-with-categorical-x/16403)

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**Author:** [@milesalanmoore](https://discourse.pymc.io/u/milesalanmoore)\
**Replies:** 2\
**Last updated:** [January 19, 2025, 2:36pm UTC](https://discourse.pymc.io/t/unexpected-behavior-with-arviz-plot-hdi-with-categorical-x/16403 "2025-01-19T14:36:34Z")

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Hi all! As a big Stan and brms user, I am really enjoying learning to fit Bayesian models in Python with the PyMC ecosystem. While attempting to refit models from my own work in bambi, I ran into some trouble plotting …

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## [Dimension Mismatch When Using ODEs With az.plot\_hdi](https://discourse.pymc.io/t/dimension-mismatch-when-using-odes-with-az-plot-hdi/16341)

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**Author:** [@r\_warr](https://discourse.pymc.io/u/r_warr)\
**Replies:** 1\
**Last updated:** [January 4, 2025, 1:04pm UTC](https://discourse.pymc.io/t/dimension-mismatch-when-using-odes-with-az-plot-hdi/16341 "2025-01-04T13:04:28Z")

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Hello, I am attempting to fit a simple model using ODEs and pymc. The model appears to run successfully, and I can plot the mean predicted posterior against the observed values. However, I can’t plot a HDI range from th…

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## [Ref Values from from arviz.plot\_posterior](https://discourse.pymc.io/t/ref-values-from-from-arviz-plot-posterior/16258)

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**Author:** [@philpj](https://discourse.pymc.io/u/philpj)\
**Replies:** 2\
**Last updated:** [December 17, 2024, 8:44am UTC](https://discourse.pymc.io/t/ref-values-from-from-arviz-plot-posterior/16258 "2024-12-17T08:44:49Z")

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Hi I was wondering how to get the orange values (Ref Vals) from the attached diagram from either arviz.plot\_posterior Plot or from another function.

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## [How to save a bart model and load it without retraining？](https://discourse.pymc.io/t/how-to-save-a-bart-model-and-load-it-without-retraining/14938)

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**Author:** [@JJ\_Py](https://discourse.pymc.io/u/JJ_Py)\
**Replies:** 1\
**Last updated:** [August 24, 2024, 12:57pm UTC](https://discourse.pymc.io/t/how-to-save-a-bart-model-and-load-it-without-retraining/14938 "2024-08-24T12:57:22Z")

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Hi, I have build a bart model for regression task. And I plan to deploy the model to a web platform. But I found a problem is that the Pymc can only save trace data (az.to\_netcdf). After reloading the trace data (az.from…

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## [Explainability of pymc predictions: which features and which direction](https://discourse.pymc.io/t/explainability-of-pymc-predictions-which-features-and-which-direction/15996)

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**Author:** [@danhislop](https://discourse.pymc.io/u/danhislop)\
**Replies:** 7\
**Last updated:** [November 10, 2024, 2:12pm UTC](https://discourse.pymc.io/t/explainability-of-pymc-predictions-which-features-and-which-direction/15996 "2024-11-10T14:12:46Z")

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I’ve developed a pymc model that is fairly accurate on the probability predictions given by pm.sample\_posterior\_predictive(idata). However I need a hint on explainability: How can I return back to the business actionabl…

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## [Arviz Inference Data Summary/to DataFrame shape errors](https://discourse.pymc.io/t/arviz-inference-data-summary-to-dataframe-shape-errors/15963)

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**Author:** [@Legstrong](https://discourse.pymc.io/u/Legstrong)\
**Replies:** 5\
**Last updated:** [October 15, 2024, 5:54am UTC](https://discourse.pymc.io/t/arviz-inference-data-summary-to-dataframe-shape-errors/15963 "2024-10-15T05:54:12Z")

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Hello all, I was having a great deal of pain getting some models to run with dimensionality issues, which I was able to fix by turning the observed y values into a numpy array then taking the 0th dimension, as in: batt…

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## [Can I get channel contribution inference from out of sample prediction](https://discourse.pymc.io/t/can-i-get-channel-contribution-inference-from-out-of-sample-prediction/14856)

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**Author:** [@JenniferSiwu](https://discourse.pymc.io/u/JenniferSiwu)\
**Replies:** 8\
**Last updated:** [October 8, 2024, 2:00pm UTC](https://discourse.pymc.io/t/can-i-get-channel-contribution-inference-from-out-of-sample-prediction/14856 "2024-10-08T14:00:10Z")

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Hi there! I am following the MMM notebook example for DelayedSaturatedMMM… I have finished the model development and fitted an out of sample predictions… My question is, from the out of samples prediction, how can i ext…

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## [View likelihood chain histories](https://discourse.pymc.io/t/view-likelihood-chain-histories/15127)

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**Author:** [@prcummins](https://discourse.pymc.io/u/prcummins)\
**Replies:** 2\
**Last updated:** [September 28, 2024, 2:19pm UTC](https://discourse.pymc.io/t/view-likelihood-chain-histories/15127 "2024-09-28T14:19:29Z")

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I am new to PyMC but have worked with Bayesian methods in the past. I have often found it useful to plot likelihood chain historioes - i.e., the values computed of the likelihood at each step of the Markov chain, for the…

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## [Overlapping graphs of az.plot\_trace()](https://discourse.pymc.io/t/overlapping-graphs-of-az-plot-trace/15117)

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**Author:** [@sflab](https://discourse.pymc.io/u/sflab)\
**Replies:** 8\
**Last updated:** [September 28, 2024, 12:15pm UTC](https://discourse.pymc.io/t/overlapping-graphs-of-az-plot-trace/15117 "2024-09-28T12:15:12Z")

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Hi all, I’m using PyMC5. When I try to show a trace plot, the outcome is weird and hard to read. Please see the screenshot below. The upper graph and lower graph overlap and their caption is hard to read, right? How…

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## [ImportError: cannot import name 'gaussian' from 'scipy.signal'](https://discourse.pymc.io/t/importerror-cannot-import-name-gaussian-from-scipy-signal/14170)

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**Author:** [@FanniLy](https://discourse.pymc.io/u/FanniLy)\
**Replies:** 7\
**Last updated:** [September 23, 2024, 8:28pm UTC](https://discourse.pymc.io/t/importerror-cannot-import-name-gaussian-from-scipy-signal/14170 "2024-09-23T20:28:39Z")

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Hi, I’m trying to import arviz, pymc and pymc\_bart packages but I got an error message showing below: --------------------------------------------------------------------------- ImportError …

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## [Arviz Compare -TypeError: Encountered error in ELPD computation of compare](https://discourse.pymc.io/t/arviz-compare-typeerror-encountered-error-in-elpd-computation-of-compare/12162)

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**Author:** [@roesta07](https://discourse.pymc.io/u/roesta07)\
**Replies:** 4\
**Last updated:** [September 10, 2024, 1:52pm UTC](https://discourse.pymc.io/t/arviz-compare-typeerror-encountered-error-in-elpd-computation-of-compare/12162 "2024-09-10T13:52:45Z")

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Hi folks; I am getting an error(as below) while trying to compare my pymc models on Google Colab. It seems like I am getting same error on pymc v5 on my local machine. I haven’t tested this code on other pymc versions; …

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## [Huge difference between MCMC posterior samples and actual data - help needed!](https://discourse.pymc.io/t/huge-difference-between-mcmc-posterior-samples-and-actual-data-help-needed/15032)

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**Author:** [@Dimlitter](https://discourse.pymc.io/u/Dimlitter)\
**Replies:** 11\
**Last updated:** [September 9, 2024, 12:53pm UTC](https://discourse.pymc.io/t/huge-difference-between-mcmc-posterior-samples-and-actual-data-help-needed/15032 "2024-09-09T12:53:29Z")

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Hi everyone, I have been working on Bayesian inference models using SEIRS framework to analyze COVID-19 and influenza co-infection data. However, I have encountered a major problem. I generated some data using the seirs…

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## [Arvix plot\_forest for Posterior Predictive Median Values?](https://discourse.pymc.io/t/arvix-plot-forest-for-posterior-predictive-median-values/15009)

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**Author:** [@buckeye17](https://discourse.pymc.io/u/buckeye17)\
**Replies:** 2\
**Last updated:** [September 7, 2024, 3:07am UTC](https://discourse.pymc.io/t/arvix-plot-forest-for-posterior-predictive-median-values/15009 "2024-09-07T03:07:52Z")

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I’d like to generate a plot which compares the dimensions in my model, similar to what plot\_forest makes. But instead of representing the HDI across each dimension, I want to plot the HDI for each dimension’s median. I…

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## [Solving question 8M9 from Bayesian Modeling and Computation in Python](https://discourse.pymc.io/t/solving-question-8m9-from-bayesian-modeling-and-computation-in-python/13975)

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**Author:** [@Tony\_Jubran](https://discourse.pymc.io/u/Tony_Jubran)\
**Replies:** 1\
**Last updated:** [September 6, 2024, 6:35pm UTC](https://discourse.pymc.io/t/solving-question-8m9-from-bayesian-modeling-and-computation-in-python/13975 "2024-09-06T18:35:34Z")

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the question is “In the GitHub repository you will find a data set of the distribution of citations of scientific papers. Use SMC-ABC to fit a g-and-k distribution to this dataset. Perform all the necessary steps to find…

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## [Noob: Algebra on chains?](https://discourse.pymc.io/t/noob-algebra-on-chains/14500)

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**Author:** [@change\_your\_prior](https://discourse.pymc.io/u/change_your_prior)\
**Replies:** 3\
**Last updated:** [September 6, 2024, 6:34pm UTC](https://discourse.pymc.io/t/noob-algebra-on-chains/14500 "2024-09-06T18:34:29Z")

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I have looked through the docs but have not seem what I am looking for, so apologies up front if this is simply me missing something. My model will run and converge without issues. Due to my specific application, I want…

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## [Different SD between pm.summary() and trace.posterior.std()](https://discourse.pymc.io/t/different-sd-between-pm-summary-and-trace-posterior-std/15022)

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**Author:** [@Dirk\_Nachbar1](https://discourse.pymc.io/u/Dirk_Nachbar1)\
**Replies:** 3\
**Last updated:** [September 6, 2024, 1:10pm UTC](https://discourse.pymc.io/t/different-sd-between-pm-summary-and-trace-posterior-std/15022 "2024-09-06T13:10:43Z")

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I have a normally distributed parameter and pm.summary() reports a smaller sd then when I use trace.posterior\[‘’\].std(axis=(0, 1)) (2 chains). Does pm.summary() not pool across chains when calculating SD?

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## [Argument for pm.plot\_hdi()](https://discourse.pymc.io/t/argument-for-pm-plot-hdi/14913)

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**Author:** [@sflab](https://discourse.pymc.io/u/sflab)\
**Replies:** 2\
**Last updated:** [August 12, 2024, 6:38am UTC](https://discourse.pymc.io/t/argument-for-pm-plot-hdi/14913 "2024-08-12T06:38:20Z")

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Hi all, I’m trying to translate a code in PyMC3 into PyMC5 but the code below doesn’t work. So if anyone know what to do, let me know. My PyMC version is 5.16.2 and python version is 3.11.6 import numpy as np import …

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