# Understanding the ar structure

**URL:** <https://discourse.mc-stan.org/t/understanding-the-ar-structure/27862>\
**Category:** Modeling\
**Tags:** techniques, specification\
**Created:** [June 17, 2022, 12:03am UTC](https://discourse.mc-stan.org/t/understanding-the-ar-structure/27862 "2022-06-17T00:03:09Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![andrjohns](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/andrjohns/32/15297_2.png) [@andrjohns](https://discourse.mc-stan.org/u/andrjohns)\
**Post date:** [June 17, 2022, 11:23am UTC](https://discourse.mc-stan.org/t/understanding-the-ar-structure/27862/2 "2022-06-17T11:23:03Z")

</div>

This is because the autocorrelation structures in `brms` use a slightly different approach, rather than directly using the previous observations

See this forum post for a bit more background: [Autocorrelation added to the model results in outrageous computation time - #2 by martinmodrak](https://discourse.mc-stan.org/t/autocorrelation-added-to-the-model-results-in-outrageous-computation-time/20018/2)

---

_[View the full topic](https://discourse.mc-stan.org/t/understanding-the-ar-structure/27862)._