# Gaussian Process -Statistical rethinking

**URL:** <https://discourse.pymc.io/t/gaussian-process-statistical-rethinking/11236>\
**Category:** v5\
**Tags:** gaussian\_process\
**Created:** [January 21, 2023, 4:48pm UTC](https://discourse.pymc.io/t/gaussian-process-statistical-rethinking/11236 "2023-01-21T16:48:30Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![roesta07](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.pymc.io/roesta07/32/6060_2.png) [@roesta07](https://discourse.pymc.io/u/roesta07)\
**Post date:** [January 28, 2023, 9:48am UTC](https://discourse.pymc.io/t/gaussian-process-statistical-rethinking/11236/3 "2023-01-28T09:48:52Z")

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Hi @fonnesbeck

> [@](#):
>
> What does the input data look like here? Is it standardized?

Yes the distance matrix Dmat is standardized where maximum value is 1 for this particular example.

> [@](#):
>
> Also, we have a [built-in Linear mean function](https://docs.pymc.io/en/v5.0.2/api/gp/generated/pymc.gp.mean.Linear.html#pymc.gp.mean.Linear) already, so no need to code your own.

Great thanks; this works fine.

> [@](#):
>
> Just for fun, try using half-normals instead of taking the absolute values of a normal (then add your offsets). Probably not the issue, but can’t hurt.

Does it mean like  
`1 + HalfNormal("etasq",0.25)` **instead of** `pm.abs(pm.Normal("etasq,1,0.25))`?

Also went into another issue, while exploring (link below), As I believe that using PYMC’s expEquad kernel function (below equation) is providing different estimates than when calculated manually! resulting in some loss in precession but I might have mis-specify something here…

> [@Comparing Manual and PYMC ExpQuad Kernel Function : DIFFERENT RESULTS](https://discourse.pymc.io/t/comparing-manual-and-pymc-expquad-kernel-function-different-results/11281):
>
> Hi all; I am trying to explore Pymc’s Gp class. and I am having a hard time replicating Mclearth’s estimates from Gaussian Process (island example). As I believe that using PYMC’s expEquad kernel function (below equation) is providing different estimates than when calculated manually, which led to loss in precision. This is ExpEquad kernel function which I am trying to replicate… [latex\_kernel] USING PYMC’S ExpQuad # Dmat is some Distance Matrix ; source link below ls=1 ## lets assume ls …

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