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Matthijs Hollanders

@matthollanders.bsky.social
508 followers 271 following 244 posts

Quantitative ecology, statistics, wildlife, field herping. Post-doctoral Research Fellow @ U of Canberra Consultant @ Quantecol, quantecol.com.au Wildlife tour guide @ Australian Wildlife Encounters, www.australianwildlifeencounters.com

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Matthijs Hollanders @matthollanders.bsky.social · 13/09/2026
I remember a tweet from @rmcelreath.bsky.social saying he sometimes modeled categorical effects as hierarchical (I assume drawn from a normal with shared scale). I reckon modeling them this way, with a sum-to-zero constraint to retain a nice intercept, *has* to be the most principled strategy.
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Reposted by Matthijs Hollanders
Jarno Vanhatalo @jarnovanhatalo.bsky.social · 08/09/2026
During the many long term ecological change projects in @rececochange.bsky.social, we have concretely learned how important long term data are. Here some thoughts on the topic 👇 Long-Term Community Data Reveal Ecological and Evolutionary Phenomena - www.annualreviews.org/content/jour...
annualreviews.org
Long-Term Community Data Reveal Ecological and Evolutionary Phenomena
Resolving the ecological and evolutionary processes affecting biodiversity requires long-term community data. By separating short-term variability from directional change and by revealing lags spannin...
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Matthijs Hollanders @matthollanders.bsky.social · 29/08/2026
Epic few days finding wildlife in the Top End.
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Matthijs Hollanders @matthollanders.bsky.social · 01/08/2026
Anyone ever use the geometric Poisson distribution? If I've implemented it correctly in Stan, it's giving me better fits than negative binomial according to PSIS-LOO-CV with a big count occupancy model.
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Matthijs Hollanders @matthollanders.bsky.social · 25/07/2026
What's the best way to get started with a local LLM? Just got a new M5 Macbook (64 GB).
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Matthijs Hollanders @matthollanders.bsky.social · 06/07/2026
Hidden Markov movement models are actually kind of annoying as (1) discretising a continuous process isn’t even all that realistic or necessarily principled and (2) it comes at high computational expense.
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Matthijs Hollanders @matthollanders.bsky.social · 02/07/2026
What are some of the flagship long term vaccine health studies (i.e. investigating causal links to autism) with open data?
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Matthijs Hollanders @matthollanders.bsky.social · 02/07/2026
Yes.
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Matthijs Hollanders @matthollanders.bsky.social · 01/07/2026
Turns out continuous time hidden Markov model-step selection functions (HMM-SSF) with unequal sampling intervals sample like a dream in @mc-stan.org🔥
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Matthijs Hollanders @matthollanders.bsky.social · 20/05/2026
occARU now supports multiseason occupancy. The package (1) detects which sites were sampled in each season and then (2) fits a continuous time dynamic occupancy model for repeatedly sampled sites. 1/n mhollanders.github.io/occARU/artic...
mhollanders.github.io
The occARU model
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Matthijs Hollanders @matthollanders.bsky.social · 07/05/2026
occARU now supports sites within regions, e.g., multiple arrays of camera traps or microphones. Random (zero-sum) region-level intercepts are estimated for both occupancy and detection, and spatial site effects are computed per-region, which is much faster! 1/2 mhollanders.github.io/occARU/
mhollanders.github.io
Occupancy Models for Automated Recording Unit (ARU) Data
Bayesian (multispecies) occupancy models for ARU data using Stan.
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Matthijs Hollanders @matthollanders.bsky.social · 05/05/2026
How do you guys deal with journals requesting revised papers with Track Changes? I don't touch Word and exclusively use Quarto.
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Matthijs Hollanders @matthollanders.bsky.social · 01/05/2026
Addressing co-author comments on your responses to reviewer comments on a manuscript you (by now) despise is probably my least favourite part of academia.
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Matthijs Hollanders @matthollanders.bsky.social · 14/04/2026
occARU: Bayesian (multispecies) occupancy models for ARU data using @mc-stan.org. Automated recording units (ARUs) like camera traps produce rich time series which warrant going beyond occupancy and focusing on detection rates. 1/n mhollanders.github.io/occARU/
mhollanders.github.io
Occupancy Models for Automated Recording Unit (ARU) Data
Bayesian (multispecies) occupancy models for ARU data using Stan.
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Matthijs Hollanders @matthollanders.bsky.social · 07/04/2026
New pre-print! I cover a range of open capture-recapture models (single survey/robust design, multistate/multievent, in (Cormack-)Jolly-Seber variants) in Stan, and provide efficient log likelihood functions. I also introduce a method to account for unequal survey intervals in the entry process.
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Matthijs Hollanders @matthollanders.bsky.social · 18/12/2025
In (Gaussian) linear models, we usually put normal priors for regression coefficients. How do we feel about putting gamma(a, a) priors in something like Poisson regression? Using rates for rates seems nice; the geometric means are still 1, meaning the priors are centered on no multiplicative effects
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Matthijs Hollanders @matthollanders.bsky.social · 29/05/2025
I can’t stand that online journals can’t format equations properly.
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Matthijs Hollanders @matthollanders.bsky.social · 18/05/2025
What do people think of this? ai-2027.com
ai-2027.com
AI 2027
A research-backed AI scenario forecast.
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Matthijs Hollanders @matthollanders.bsky.social · 13/05/2025
Hey #stats people, what do we think about interpreting coefficients in cloglog binomial regressions? Since everyone hates odds ratios I wonder if interpreting hazard ratios is easier.
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Matthijs Hollanders @matthollanders.bsky.social · 01/05/2025
Why do we peer review for free?
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Matthijs Hollanders @matthollanders.bsky.social · 03/04/2025
I need some help with parameterising a latent simplex, so a set of latent probabilities that sum to 1. Can anyone have a yarn?
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Matthijs Hollanders @matthollanders.bsky.social · 02/04/2025
Hazard rates FTW 🎉
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Matthijs Hollanders @matthollanders.bsky.social · 29/03/2025
brms is one of the most amazing R packages ever. Nevertheless I can't get myself to use it for my own work because nothing beats coding up your own models where you have ultimate control and insight into what's going on. There remains a "black box" element unless you are deeply familiar with it.
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Matthijs Hollanders @matthollanders.bsky.social · 17/03/2025
Working on a multisite/multistate/robust design Jolly-Seber model in Stan where I need to marginalise (1) the entry occasion of each individual and (2) the sub-area within each site where each individual enters. 😮‍💨
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Reposted by Matthijs Hollanders
Quantecol @quantecol.bsky.social · 24/02/2025
We just updated our HMM blog by applying the backward sampling algorithm to recover the posterior distributions of latent states. Check it out! quantecol.com.au/blog/hmm-in-...
quantecol.com.au
Ecological Modeling in Stan
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Matthijs Hollanders @matthollanders.bsky.social · 21/02/2025
Hey movement ecology people, are the models implemented in the #ctmm R package essentially just GPs fit to location data?
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Matthijs Hollanders @matthollanders.bsky.social · 12/02/2025
Launched a bsky page for the ecological stats consultancy, give us a follow!
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Matthijs Hollanders @matthollanders.bsky.social · 06/02/2025
Those are good looking plots.
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Reposted by Matthijs Hollanders
Nick Clark 💹 @njclark.bsky.social · 04/02/2025
Another video in my series on applied time series and forecasting with the {mvgam} #rstats 📦. This one introduces State Space hierarchical GAMs and GPs for tackling multivariate series youtu.be/2POK_FVwCHk?...
youtu.be
Time series in R and Stan using the mvgam package: hierarchical GAMs
YouTube video by Nicholas Clark
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Matthijs Hollanders @matthollanders.bsky.social · 04/02/2025
New blog post! I show how to marginalise discrete variables from Bayesian ecological models in Stan and how to recover their posterior distributions after estimation. I cover occupancy and N-mixture models using multiple parameterisations and model types. quantecol.com.au/blog/margina...
quantecol.com.au
Quantecol - Marginalisation
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Matthijs Hollanders @matthollanders.bsky.social · 07/01/2025
I've been looking at different parameterisations of multi-season occupancy models, and it seems that dynamic (with colonisation and emigration) and auto-logistic models aren't all that different. Auto-logistic might be preferred with \alpha being a sort of average log odds. @masonfidino.bsky.social
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Matthijs Hollanders @matthollanders.bsky.social · 01/01/2025
I’ve been enjoying a restful Christmas break, and one of the highlights was this python selecting a carefully placed tin stack to lay her eggs.
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Matthijs Hollanders @matthollanders.bsky.social · 27/11/2024
Hey guys, how do you do posterior predictive checks for GPs?
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Matthijs Hollanders @matthollanders.bsky.social · 17/11/2024
It’s hard to beat an afternoon of herping our Gondwana rainforests. Big coastal carpet python under tin and a gravid snake-tooth skink on the crawl were amongst the many finds over the weekend.
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Matthijs Hollanders @matthollanders.bsky.social · 13/11/2024
Paul Bürkner's brms book is really good. paulbuerkner.com/software/brm...
paulbuerkner.com
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Matthijs Hollanders @matthollanders.bsky.social · 12/11/2024
I forgot about this app until just now. Might use my first post in a while to shill my blog, where I recently wrote a new post about using Gaussian processes for random temporal and/or site effects in (ecological) models. quantecol.com.au/blog/gaussia...
quantecol.com.au
Quantecol - Default to Gaussian processes
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Matthijs Hollanders @matthollanders.bsky.social · 09/05/2024
As a first post on Bluesky I'll shill our recently launched #statistics blog, where we'll be focusing on applied statistical ecology in particular. Our first post details a scalable method for fitting increasingly complex hidden Markov models in Stan. quantecol.com.au/blog/hmm-in-...
quantecol.com.au
Quantecol - Ecological Modeling in Stan
May 5, 2024
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