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Aki Vehtari

@avehtari.bsky.social

6.1K followers 240 following 210 posts

Professor in computational Bayesian modeling at Aalto University, Finland. Bayesian Data Analysis 3rd ed, Regression and Other Stories, and Active Statistics co-author. #mcmc_stan and #arviz developer. Web page https://users.aalto.fi/~ave/

users.aalto.fi

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Aki Vehtari @avehtari.bsky.social · Aug 2

All three books I've co-authored are freely available online for non-commercial use:

- #Bayesian Data Analysis, 3rd ed (aka BDA3) at stat.columbia.edu/~gelman/book/

- #Regression and Other Stories at avehtari.github.io/ROS-Examples/

- Active Statistics at avehtari.github.io/ActiveStatis...

The cover of Bayesian Data Analysis book

The cover of Regression and Other Stories book

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Reposted by Aki Vehtari

tj ♏️ahr @tjmahr.com · 3d

note that in the ggplot2 the default pointsize is not a constant anymore

GeomPoint$default_aes
#> Aesthetic mapping:
#> * `shape` -> `from_theme(pointshape)`
#> * `colour` -> `from_theme(colour %||% ink)`
#> * `fill` -> `from_theme(fill %||% NA)`
#> * `size` -> `from_theme(pointsize)`

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Reposted by Aki Vehtari

MC Stan @mc-stan.org · 3d

Have you made a package on top of Stan? Do you have a cool trick to make Stan faster or create a fancy model? Would you like to make a guest post at Stan blog blog.mc-stan.org?

Send me a private message if you are interested (and note that with our current blog plan we don't have MathJax support)

The Stan Blog

blog.mc-stan.org

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Aki Vehtari @avehtari.bsky.social · 5d

Years ago I did read Takeuchi's equations and they were understandable, because maths!

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Reposted by Aki Vehtari

Martin Modrák @modrakm.bsky.social · 5d

If you feel so inclined, I run a Mastodon instance bayes.club and try to make it a nice place and you can join if you like. I know some people have strong opinions on this and some have had bad experience on Mastodon. And that's all fair and I won't dispute that, there's a lot of work to do.

Bayes Club

A community of statisticians using Bayesian methods.

bayes.club

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Aki Vehtari @avehtari.bsky.social · 6d

I'm looking for a doctoral student with Bayesian background to work on Bayesian workflow and cross-validation (see my publication list users.aalto.fi/~ave/publica... for my recent work) at Aalto University.

Apply through the ELLIS PhD program (dl October 31) ellis.eu/news/ellis-p...

ELLIS PhD Program: Call for Applications 2025

The ELLIS mission is to create a diverse European network that promotes research excellence and advances breakthroughs in AI, as well as a pan-European PhD program to educate the next generation of AI...

ellis.eu

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Aki Vehtari @avehtari.bsky.social · 6d

I was two weeks on vacation in sunny and warm Sardinia, Italy, played in a beach ultimate tournament (this year we were the 4th best team in the world, and the best non-USA team), learned to kite surf, snorkeled, and ate lots of delicious food and gelato

Photo of many kite surfers at Punta Trettu, Sardinia

Aki Vehtari @avehtari.bsky.social · 24d

R-multiverse Production repository r-multiverse.org/production.h... looks great for those who prefer CRAN level stability (actually a bit more stable) for R packages, but want to also use high quality packages that are not in CRAN (like CmdStanR)

Production repository – R-multiverse

A community-curated dual R package repository, powered by R-universe

r-multiverse.org

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Reposted by Aki Vehtari

Vincent Arel-Bundock @vincentab.bsky.social · 25d

Whoa—my book is up for pre-order!

𝐌𝐨𝐝𝐞𝐥 𝐭𝐨 𝐌𝐞𝐚𝐧𝐢𝐧𝐠: 𝐇𝐨𝐰 𝐭𝐨 𝐈𝐧𝐭𝐞𝐫𝐩𝐫𝐞𝐭 𝐒𝐭𝐚𝐭 & 𝐌𝐋 𝐌𝐨𝐝𝐞𝐥𝐬 𝐢𝐧 #Rstats 𝐚𝐧𝐝 #PyData

The book presents an ultra-simple and powerful workflow to make sense of ± any model you fit

The web version will stay free forever and my proceeds go to charity.

tinyurl.com/4fk56fc8

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Reposted by Aki Vehtari

Jarno Vanhatalo @jarnovanhatalo.bsky.social · 24d

NordStat will be in Helsinki in 1-4 June, 2026. Website and preliminary program have been published:
www.helsinki.fi/en/conferenc...

30th Nordic Conference in Mathematical Statistics | University of Helsinki

1-4 June 2026, University of Helsinki, Finland

www.helsinki.fi

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Reposted by Aki Vehtari

MC Stan @mc-stan.org · 25d

MC Stan is here! Follow for the latest Stan news, and tag if you want us to repost your posts about new papers, packages, courses, etc. about Stan

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Reposted by Aki Vehtari

Andrew Gelman et al. @statmodeling.bsky.social · 26d

Stats and ML postdoc and permanent hiring season officially open at Flatiron
statmodeling.stat.columbia.edu/2025/09/16/s...

Stats and ML postdoc and permanent hiring season officially open at Flatiron | Statistical Modeling, Causal Inference, and Social Science

statmodeling.stat.columbia.edu

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Reposted by Aki Vehtari

Josef Fruehwald @jofrhwld.bsky.social · 29d

for the late nite crew: stat_manual() is super good

Working with stat_manual() – Væl Space

jofrhwld.github.io

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Reposted by Aki Vehtari

Adrian Raftery @adrianraftery.bsky.social · Sep 13

Our paper, “Optimal pandemic control strategies …” bmcglobalpublichealth.biomedcentral.com/articles/10.... w @nickirons.bsky.social, just published.Takeaway: U.S. COVID-19 school closures were not cost-effective, but other measures were. medicalxpress.com/news/2025-09...

Optimal pandemic control strategies and cost-effectiveness of COVID-19 non-pharmaceutical interventions in the United States - BMC Global and Public Health

Background Non-pharmaceutical interventions (NPIs) in response to the COVID-19 pandemic necessitated a trade-off between the health impacts of viral spread and the social and economic costs of restric...

bmcglobalpublichealth.biomedcentral.com

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Reposted by Aki Vehtari

Thomas Lin Pedersen @thomasp85.com · Sep 11

I am beyond excited to announce that ggplot2 4.0.0 has just landed on CRAN.

It's not every day we have a new major #ggplot2 release but it is a fitting 18 year birthday present for the package.

Get an overview of the release in this blog post and be on the lookout for more in-depth posts #rstats

ggplot2 4.0.0

A new major version of ggplot2 has been released on CRAN. Find out what is new here.

www.tidyverse.org

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Reposted by Aki Vehtari

Kamélia Daudel @kdau.bsky.social · Sep 11

The Journal-to-Conference track is back at AISTATS🌴!

The track invites authors of papers published or accepted after January 1st, 2024 in AoS, Biometrika, JASA, JMLR and JRSS B to present their work as posters at #AISTATS2026 in Tangier, Morocco (May 2nd-5th 2026).

📅 Deadline: 31 January 2026

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Reposted by Aki Vehtari

Adam L @lauretig.bsky.social · Sep 10

Simon Wood, the GOAT of generalized additive models & creator of the mgcv #rstats package, has an Annual Review of Statistics essay on GAMs, available open access #statssky #mlsky

www.annualreviews.org/content/jour...

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Reposted by Aki Vehtari

LMU Open Science Center @lmu-osc.bsky.social · Sep 10

💡 Explore how practices from distributed, open-source software can make science more professional, open, and collaborative! Attend the “Science as amateur software development” lecture by Prof. Dr. @rmcelreath.bsky.social on Wed 17 Sept, 9:00.
👉 Register here: www.pretix.osc.lmu.de/lmu-osc/OSSS...

Promotional poster for the LMU Open Science Center Summer School 2025 Public Lecture. The poster features a photo of speaker Prof. Dr. Richard McElreath. The text states the lecture focuses on science as amateur software development, time and date of lecture being 9:00-10:00 CEST on Wednesday September 17 2025, and instructions to register online. Logos of LMU Open Science Center, LMU, and Universitätsbibliothek München are displayed at the bottom.

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Aki Vehtari @avehtari.bsky.social · Sep 7

Tidybayes and ggdist might have something useful for your packages

Reposted by Aki Vehtari

Jarno Vanhatalo @jarnovanhatalo.bsky.social · Sep 3

We are seeking a postdoctoral researcher in statistics to develop methods for analyzing large scale biodiversity and ecosystem function data at the University of Helsinki.

This is a great opportunity for someone who wants to do advanced Bayesian modeling with direct link to real world applications.

Research Centre For Ecological Change @rececochange.bsky.social · Sep 3

📢 Post doc! Want to join our team?

We are looking for 3 post docs in biodiversity science, genetic indicator assessment, and ecological statistics for a fixed term of 2 years!

Come unravel the drivers and consequences of global change on biodiversity with us!

DL 24.9.
#universityofhelsinki

3 Post doc positions in biodiversity science, genetic indicator assessment and ecological statistics

jobs.helsinki.fi

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Aki Vehtari @avehtari.bsky.social · Sep 3

And the discrete rootogram with white background

Aki Vehtari @avehtari.bsky.social · Sep 3

- Add x argument to ppc_error_binned() and ppc_error_scatter_avg() to control x axis
- Add discrete argument to pp[cd]_stat() to support discrete stats

3/3

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Aki Vehtari @avehtari.bsky.social · Sep 3

other new features
- PPC “avg” functions gain a stat argument to set the summary function
- ppc_error_scatter_avg_vs_x(x = some_expression) labels the x axis with some_expression.
- New quantile dot plot functions pp[cd]_dots()

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Aki Vehtari @avehtari.bsky.social · Sep 3

bayesplot 1.14.0 CRAN release mc-stan.org/bayesplot/ with contributions from @tjmahr.com, Behram Ulukır, and @teemusailynoja.bsky.social

My favorite new feature is the discrete style ppc_rootogram() as proposed in teemusailynoja.github.io/visual-predi... and shown below

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A discrete rootgram plot. The unmodified counts are displayed on the vertical axis, while using square root scaling for the axis, thus enabling direct reading of the count frequencies. The predictions are displayed as light blue points and interval lines. The observations are overlaid with darker points, except the observations outside the predictive credible intervals are highlighted in red.

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Aki Vehtari @avehtari.bsky.social · Sep 2

Productive procrastination by making 7 PRs to fix Stan doc issues (still couple issues I think I can help with)

Aki Vehtari @avehtari.bsky.social · Sep 2

- new hypergeometric functions
- C++17 features improve performance
CmdStan:
- easier to run multiple chains with one call to the executable
- improved error messages
- default output use more digits to reduce constraint errors when reusing output
- laplace_sample and Pathfinder use less memory
2/2

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