# \#polynomial-chaos **URL:** https://openturns.discourse.group/tag/polynomial-chaos/2.md [Latest](https://openturns.discourse.group/latest.md) · [Categories](https://openturns.discourse.group/categories.md) · [Tags](https://openturns.discourse.group/tags.md) --- ## [The hyperbolic enumeration function can be slow when q = 1](https://openturns.discourse.group/t/the-hyperbolic-enumeration-function-can-be-slow-when-q-1/277)
**Author:** [@MichaelBaudin](https://openturns.discourse.group/u/MichaelBaudin)\ **Replies:** 0\ **Last updated:** [March 26, 2023, 4:17pm UTC](https://openturns.discourse.group/t/the-hyperbolic-enumeration-function-can-be-slow-when-q-1/277 "2023-03-26T16:17:10Z")
Hi! I created a polynomial chaos expansion of a function in relatively large dimension using regression and the LARS selection method. This may require to use the hyperbolic enumeration function. It appears, however, th… --- ## [PCE with discrete distribution](https://openturns.discourse.group/t/pce-with-discrete-distribution/223)
**Author:** [@herve.lebail](https://openturns.discourse.group/u/herve.lebail)\ **Replies:** 4\ **Last updated:** [November 28, 2024, 12:27pm UTC](https://openturns.discourse.group/t/pce-with-discrete-distribution/223 "2024-11-28T12:27:01Z")
Hello everybody, With one of my student we are in the process of building a PCE for a function of continuous and discrete distribution of parameters. To put it simple we are trying to fit functions of the type (see pro… --- ## [PCE design matrix and coefficient fit](https://openturns.discourse.group/t/pce-design-matrix-and-coefficient-fit/265)
**Author:** [@dlouk](https://openturns.discourse.group/u/dlouk)\ **Replies:** 6\ **Last updated:** [November 22, 2024, 2:42pm UTC](https://openturns.discourse.group/t/pce-design-matrix-and-coefficient-fit/265 "2024-11-22T14:42:53Z")
Greetings, I am trying to reproduce the results of the example “Create a polynomial chaos for the Ishigami function: a quick start guide to polynomial chaos” (Create a polynomial chaos for the Ishigami function: a quick… --- ## [Derivative based Global sensitivity measures from Polynomial Chaos Expansion](https://openturns.discourse.group/t/derivative-based-global-sensitivity-measures-from-polynomial-chaos-expansion/320)
**Author:** [@gowthamr](https://openturns.discourse.group/u/gowthamr)\ **Replies:** 3\ **Last updated:** [August 28, 2024, 8:17am UTC](https://openturns.discourse.group/t/derivative-based-global-sensitivity-measures-from-polynomial-chaos-expansion/320 "2024-08-28T08:17:37Z")
Hi, I could see that the PC-based sensitivity analysis is implemented in OpenTURNS. Further, I would like to request whether OpenTURNS can also implement the Derivative-based Global sensitivity measures using PCE. The… --- ## [Metamodel to substitute a Code\_Aster study](https://openturns.discourse.group/t/metamodel-to-substitute-a-code-aster-study/330)
**Author:** [@pauline6](https://openturns.discourse.group/u/pauline6)\ **Replies:** 6\ **Last updated:** [November 30, 2023, 4:58pm UTC](https://openturns.discourse.group/t/metamodel-to-substitute-a-code-aster-study/330 "2023-11-30T16:58:52Z")
Good evening everyone, I have done several simulations through Code\_Aster to finally get a complete and nice stress strain curve. Thanks to the experimental curve, I am able to do a calibration and then imitate as bette… --- ## [Unrealistic predictions with PCE](https://openturns.discourse.group/t/unrealistic-predictions-with-pce/302)
**Author:** [@amentani](https://openturns.discourse.group/u/amentani)\ **Replies:** 3\ **Last updated:** [June 28, 2023, 1:12pm UTC](https://openturns.discourse.group/t/unrealistic-predictions-with-pce/302 "2023-06-28T13:12:37Z")
Hi all, Months ago I used the PCE algorithm to emulate the response of a simple FE model. Nine input parameters were varied and combined in a LH sample for what FEA were run and two output were stored to be predicted b… --- ## [Impossible truncature degree for Functional Chaos](https://openturns.discourse.group/t/impossible-truncature-degree-for-functional-chaos/216)
**Author:** [@SarahIaquinta](https://openturns.discourse.group/u/SarahIaquinta)\ **Replies:** 4\ **Last updated:** [November 21, 2022, 4:00pm UTC](https://openturns.discourse.group/t/impossible-truncature-degree-for-functional-chaos/216 "2022-11-21T16:00:41Z")
Hello, I am currently implementing a Functional Chaos (PCE) metamodel. I have 3 input parameters and around 800 samples. According to the rule of thumbs to avoid matrix singularities, the truncature degree should not be… --- ## [PCE study with inputs distributions](https://openturns.discourse.group/t/pce-study-with-inputs-distributions/233)
**Author:** [@Flore](https://openturns.discourse.group/u/Flore)\ **Replies:** 1\ **Last updated:** [September 23, 2022, 8:21pm UTC](https://openturns.discourse.group/t/pce-study-with-inputs-distributions/233 "2022-09-23T20:21:21Z")
Hello Previously (and basically) I build polynomial chaos metamodels with first constructor ot.FunctionalChaosAlgorithm(input\_sample, output\_rsample\[:,outputIndex\]) And I managed to get good results for my first outpu… --- ## [FunctionalChaosAlgorithm with your own orthonormal basis construction](https://openturns.discourse.group/t/functionalchaosalgorithm-with-your-own-orthonormal-basis-construction/143)
**Author:** [@lcoelho](https://openturns.discourse.group/u/lcoelho)\ **Replies:** 2\ **Last updated:** [September 15, 2022, 1:29pm UTC](https://openturns.discourse.group/t/functionalchaosalgorithm-with-your-own-orthonormal-basis-construction/143 "2022-09-15T13:29:42Z")
Hi, Using ot.FunctionalChaosAlgorithm(), I would like to know if it’s possible to give your own construction of the orthonormal basis in the AdaptativeStrategy(). Best, Ludovic --- ## [IntegrationStrategy guidelines](https://openturns.discourse.group/t/integrationstrategy-guidelines/220)
**Author:** [@schueller](https://openturns.discourse.group/u/schueller)\ **Replies:** 2\ **Last updated:** [August 2, 2022, 5:24pm UTC](https://openturns.discourse.group/t/integrationstrategy-guidelines/220 "2022-08-02T17:24:37Z")
Are there any tips on the DOEs to use with IntegrationStrategy ? In the integration example with the beam from the doc, GaussProductExperiment works great: But if I try to use anything else (MC, QMC, LHS) the Q2 is o… --- ## [Possible evaluation of Sobol indices directly from the FunctionalChaosAlgorithm?](https://openturns.discourse.group/t/possible-evaluation-of-sobol-indices-directly-from-the-functionalchaosalgorithm/207)
**Author:** [@SarahIaquinta](https://openturns.discourse.group/u/SarahIaquinta)\ **Replies:** 2\ **Last updated:** [May 11, 2022, 11:58am UTC](https://openturns.discourse.group/t/possible-evaluation-of-sobol-indices-directly-from-the-functionalchaosalgorithm/207 "2022-05-11T11:58:16Z")
Hello, Is there a way to compute the Sobol indices directly from the FunctionalChaosAlgorithm class? Regards, Sarah --- ## [Gradient and Hessian for polynomial chaos metamodels](https://openturns.discourse.group/t/gradient-and-hessian-for-polynomial-chaos-metamodels/177)
**Author:** [@fabdlhm](https://openturns.discourse.group/u/fabdlhm)\ **Replies:** 2\ **Last updated:** [February 10, 2022, 3:46pm UTC](https://openturns.discourse.group/t/gradient-and-hessian-for-polynomial-chaos-metamodels/177 "2022-02-10T15:46:27Z")
Hi, i have constructed a polynomial chaos metamodel of a function with input dimension dx and output dimension dy, and i would like to evaluate the gradient of this metamodel in a vectorized way, i.e. for an input array… --- ## [Question about metamodels choice](https://openturns.discourse.group/t/question-about-metamodels-choice/169)
**Author:** [@Flore](https://openturns.discourse.group/u/Flore)\ **Replies:** 9\ **Last updated:** [December 2, 2021, 2:04pm UTC](https://openturns.discourse.group/t/question-about-metamodels-choice/169 "2021-12-02T14:04:15Z")
Hello I am currently building with openturns chaos polynomial and kriging metamodels I have 20 input parameters and 3 outputs (scalars) I build metamodel for each output independantly with a sample of 200 computation… --- ## [Message while building chaos polynomials](https://openturns.discourse.group/t/message-while-building-chaos-polynomials/167)
**Author:** [@Flore](https://openturns.discourse.group/u/Flore)\ **Replies:** 2\ **Last updated:** [November 24, 2021, 9:22am UTC](https://openturns.discourse.group/t/message-while-building-chaos-polynomials/167 "2021-11-24T09:22:31Z")
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 2… --- ## [Questions diverses sur l'utilisation openturns](https://openturns.discourse.group/t/questions-diverses-sur-lutilisation-openturns/64)
**Author:** [@Flore](https://openturns.discourse.group/u/Flore)\ **Replies:** 1\ **Last updated:** [March 21, 2021, 2:39pm UTC](https://openturns.discourse.group/t/questions-diverses-sur-lutilisation-openturns/64 "2021-03-21T14:39:21Z")
Bonjour Je suis une nouvelle utilisatrice d’OpenTurns. Je me suis définie un cas d’étude (simulation en 2D faisant appel à un logiciel interne), j’ai paramétré ce cas, j’ai défini le script python qui permet de générer … --- ## [Error while building chao algo](https://openturns.discourse.group/t/error-while-building-chao-algo/84)
**Author:** [@Flore](https://openturns.discourse.group/u/Flore)\ **Replies:** 13\ **Last updated:** [February 20, 2021, 7:07pm UTC](https://openturns.discourse.group/t/error-while-building-chao-algo/84 "2021-02-20T19:07:02Z")
Hi everyone ! I build a sample from my physics simulation tools. From this sample I would like to build metamodel. I first try a chaos algo. But an error occured and I don’t understand why. I generate my sample with LH… --- ## [Undersampled least squares solution in FunctionalChaosAlgorithm](https://openturns.discourse.group/t/undersampled-least-squares-solution-in-functionalchaosalgorithm/79)
**Author:** [@dlouk](https://openturns.discourse.group/u/dlouk)\ **Replies:** 1\ **Last updated:** [December 27, 2020, 2:30pm UTC](https://openturns.discourse.group/t/undersampled-least-squares-solution-in-functionalchaosalgorithm/79 "2020-12-27T14:30:17Z")
Greetings, I construct a PCE model using algo = ot.FunctionalChaosAlgorithm(train\_in, train\_out, jpdf, adaptiveStrategy, projectionStrategy), with projectionStrategy = ot.LeastSquaresStrategy() adaptiveStrategy = o… --- ## [Chaos Vs Saltelli](https://openturns.discourse.group/t/chaos-vs-saltelli/70)
**Author:** [@jmp](https://openturns.discourse.group/u/jmp)\ **Replies:** 6\ **Last updated:** [December 23, 2020, 1:50pm UTC](https://openturns.discourse.group/t/chaos-vs-saltelli/70 "2020-12-23T13:50:00Z")
Hi, I have performed a bunch of 100k simulation using a satellite reentry software and I’m trying to analyse its sensitivity to perturbations in the input parameters. Using the PCE approach I get results that are consi…