# Message while building chaos polynomials

**URL:** <https://openturns.discourse.group/t/message-while-building-chaos-polynomials/167>\
**Category:** Methodology\
**Tags:** polynomial-chaos\
**Created:** [November 23, 2021, 5:38pm UTC](https://openturns.discourse.group/t/message-while-building-chaos-polynomials/167 "2021-11-23T17:38:24Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Flore](https://avatars.discourse-cdn.com/v4/letter/f/3d9bf3/32.png) [@Flore](https://openturns.discourse.group/u/Flore)\
**Post date:** [November 23, 2021, 5:38pm UTC](https://openturns.discourse.group/t/message-while-building-chaos-polynomials/167/1 "2021-11-23T17:38:24Z")

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![image](https://global.discourse-cdn.com/free1/uploads/openturns/original/1X/95aba77e19be4f4511bf48cee51e7ea33f8572fa.png)  
Hello

I am currently building with openturns chaos polynomial metamodels  
I have 20 input parameters  
See screenshot joined for particular message I see during metamodel building  
I build metamodel with a sample of 200 computations (LHS)  
I compute predictivity factor Q2 with test sample of 20 other computations  
I obtain a Q2 factor very near of 1 so it seems good

I build my metamodel with basic instructions :

```python
chaosalgo = ot.FunctionalChaosAlgorithm(input_sample, output_rsample[:,outputIndex])
chaosalgo.run()
chaosalgo_result = chaosalgo.getResult()
chaosalgo_metamodel = chaosalgo_result.getMetaModel()

```

thanks in advance for your advises

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**Author:** ![regislebrun](https://yyz2.discourse-cdn.com/free1/user_avatar/openturns.discourse.group/regislebrun/32/154_2.png) [@regislebrun](https://openturns.discourse.group/u/regislebrun)\
**Post date:** [November 24, 2021, 8:59am UTC](https://openturns.discourse.group/t/message-while-building-chaos-polynomials/167/2 "2021-11-24T08:59:04Z")

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Hi Flore,  
This message comes from the part of the algorithm dedicated to the automatic construction of a joint distribution of your input sample. It is done by trying all the continuous parametric models and some of them fail e.g. because you have negative values and try positive models. At the end, if no parametric model is accepted a nonparametric model is built (Histogram). So these messages are harmless and you can simply ignore them.

Cheers

Régis

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<div class="post-metadata">

**Author:** ![Flore](https://avatars.discourse-cdn.com/v4/letter/f/3d9bf3/32.png) [@Flore](https://openturns.discourse.group/u/Flore)\
**Post date:** [November 24, 2021, 9:22am UTC](https://openturns.discourse.group/t/message-while-building-chaos-polynomials/167/3 "2021-11-24T09:22:31Z")

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thanks Régis !