# Latest **URL:** https://uqworld.org/latest.md [Latest](https://uqworld.org/latest.md) · [Categories](https://uqworld.org/categories.md) · [Tags](https://uqworld.org/tags.md) --- ## [Wait, what is UQWorld again?](https://uqworld.org/t/wait-what-is-uqworld-again/100)
**Author:** [@damarginal](https://uqworld.org/u/damarginal)\ **Replies:** 0\ **Last updated:** [January 31, 2019, 3:26pm UTC](https://uqworld.org/t/wait-what-is-uqworld-again/100 "2019-01-31T15:26:19Z")
This blog post is jointly written by S. Marelli, D. Wicaksono, and B. Sudret. Welcome to UQWorld! UQWorld is the brand new online community for uncertainty quantification (UQ) practitioners, researchers, and, why n… --- ## [Welcome to UQWorld!](https://uqworld.org/t/welcome-to-uqworld/8)
**Author:** [@system](https://uqworld.org/u/system)\ **Replies:** 0\ **Last updated:** [October 29, 2018, 2:00pm UTC](https://uqworld.org/t/welcome-to-uqworld/8 "2018-10-29T14:00:47Z")
UQWorld is an online community for you to connect with fellow UQ practitioners across scientific disciplines to discuss the practice of UQ in science and engineering, use cases, and best practices. Here, you can share an… --- ## [Candidate sample update in UQLab ALR](https://uqworld.org/t/candidate-sample-update-in-uqlab-alr/9179)
**Author:** [@David\_Sebastian\_Calp](https://uqworld.org/u/David_Sebastian_Calp)\ **Replies:** 2\ **Last updated:** [July 29, 2026, 6:34pm UTC](https://uqworld.org/t/candidate-sample-update-in-uqlab-alr/9179 "2026-07-29T18:34:57Z")
Hello, I am using the Active Learning Reliability (ALR) framework in UQLab and would like to better understand how the candidate populations are handled internally during the enrichment process. My understanding is tha… --- ## [Assigning Gaussian Probability Distributions to Strictly Positive Random Variables](https://uqworld.org/t/assigning-gaussian-probability-distributions-to-strictly-positive-random-variables/9132)
**Author:** [@Elias](https://uqworld.org/u/Elias)\ **Replies:** 1\ **Last updated:** [July 21, 2026, 10:48am UTC](https://uqworld.org/t/assigning-gaussian-probability-distributions-to-strictly-positive-random-variables/9132 "2026-07-21T10:48:27Z")
Hello Everybody! I am new to the field, so forgive me for any silly questions. I am trying to assign probability distributions to my uncertain inputs, and the first probability distribution that comes to mind is the ove… --- ## [How is the acceptance probability of MH algorithm computed in practice?](https://uqworld.org/t/how-is-the-acceptance-probability-of-mh-algorithm-computed-in-practice/9162)
**Author:** [@GuillaumeGru](https://uqworld.org/u/GuillaumeGru)\ **Replies:** 1\ **Last updated:** [July 10, 2026, 8:42am UTC](https://uqworld.org/t/how-is-the-acceptance-probability-of-mh-algorithm-computed-in-practice/9162 "2026-07-10T08:42:42Z")
Dear UQworld community, I am currently reading the fundamentals of Bayesian inversion in order to fully understand what UQ\[py\]Lab has in its core. (I am using it to solve an inverse problem in hydrogeophysics). I think… --- ## [Sobol Indices by using Polynomial Chaos Expansion](https://uqworld.org/t/sobol-indices-by-using-polynomial-chaos-expansion/9184)
**Author:** [@SimoneRomani12](https://uqworld.org/u/SimoneRomani12)\ **Replies:** 2\ **Last updated:** [July 1, 2026, 8:13am UTC](https://uqworld.org/t/sobol-indices-by-using-polynomial-chaos-expansion/9184 "2026-07-01T08:13:20Z")
Dear all, I would like to kindly ask you a doubt about Sobol indices computed by Polynomial Chaos coefficients. Some time ago, considering a particular case of study, I tried to compute Sobol indices based on Polynomial… --- ## [Possible numerical edge case in QR-based ML objective with zero custom trend](https://uqworld.org/t/possible-numerical-edge-case-in-qr-based-ml-objective-with-zero-custom-trend/9181)
**Author:** [@Alessandro\_Baravelli](https://uqworld.org/u/Alessandro_Baravelli)\ **Replies:** 1\ **Last updated:** [June 10, 2026, 2:37pm UTC](https://uqworld.org/t/possible-numerical-edge-case-in-qr-based-ml-objective-with-zero-custom-trend/9181 "2026-06-10T14:37:43Z")
When the trend design matrix is identically zero, qr(Ftilde,0) may return a nonzero orthonormal vector Q with R=0. This is a valid QR factorization, but using Q to project Ytilde removes a component of Ytilde even though… --- ## [Python version for UQpyLab](https://uqworld.org/t/python-version-for-uqpylab/9176)
**Author:** [@ibrahim\_hanif](https://uqworld.org/u/ibrahim_hanif)\ **Replies:** 3\ **Last updated:** [June 10, 2026, 2:23pm UTC](https://uqworld.org/t/python-version-for-uqpylab/9176 "2026-06-10T14:23:07Z")
Hi, I have recently started to use the UQpyLab framework and firstly would like to say great work! with these very comprehensive and detailed packages (in matlab and python) you’ve developed :smiley: I wish to combine … --- ## [UQ\[py\]Lab "ConnectTimeoutError" for long analysis](https://uqworld.org/t/uq-py-lab-connecttimeouterror-for-long-analysis/9169)
**Author:** [@GuillaumeGru](https://uqworld.org/u/GuillaumeGru)\ **Replies:** 0\ **Last updated:** [April 13, 2026, 8:56am UTC](https://uqworld.org/t/uq-py-lab-connecttimeouterror-for-long-analysis/9169 "2026-04-13T08:56:14Z")
Dear UQWorld community, I have been running the Bayesian Inference (BI) module of UQ\[py\]Lab to solve an inverse problem with PCE metamodels. The BI has already worked successfully for some synthetic test cases. I am us… --- ## [Input variables - PCE](https://uqworld.org/t/input-variables-pce/9168)
**Author:** [@SimoneRomani12](https://uqworld.org/u/SimoneRomani12)\ **Replies:** 1\ **Last updated:** [April 9, 2026, 2:57pm UTC](https://uqworld.org/t/input-variables-pce/9168 "2026-04-09T14:57:43Z")
Dear users, I am writing to kindly ask if it is possible to generate a PCE by using a DOE composed by continuous and discrete random variables. Specifically, I am working with 10 initial variables: 9 variables are conti… --- ## [UQLab V2.2 Released: New Surrogate Model Benchmarking Module](https://uqworld.org/t/uqlab-v2-2-released-new-surrogate-model-benchmarking-module/9167)
**Author:** [@ste](https://uqworld.org/u/ste)\ **Replies:** 0\ **Last updated:** [March 18, 2026, 2:44pm UTC](https://uqworld.org/t/uqlab-v2-2-released-new-surrogate-model-benchmarking-module/9167 "2026-03-18T14:44:29Z")
Dear UQWorld Community, Since its release, UQLab has grown into a reference platform for uncertainty quantification, recently reaching nearly 10,000 users in 100 countries. Today, we are announcing the release of UQLab v… --- ## [Calculating the PCE coefficients with Gaussian quadrature using existing data](https://uqworld.org/t/calculating-the-pce-coefficients-with-gaussian-quadrature-using-existing-data/3517)
**Author:** [@chenhao](https://uqworld.org/u/chenhao)\ **Replies:** 5\ **Last updated:** [March 4, 2026, 5:34pm UTC](https://uqworld.org/t/calculating-the-pce-coefficients-with-gaussian-quadrature-using-existing-data/3517 "2026-03-04T17:34:38Z")
hello everyone My uncertainty quantification problem doesn’t have a definite function relationship between input and output because the output is calculated by CFD based on corresponding input values. Which means Unable… --- ## [MOMap definition for multiple models with multidimensional outputs (UQ\[py\]Lab - Bayesian inversion)](https://uqworld.org/t/momap-definition-for-multiple-models-with-multidimensional-outputs-uq-py-lab-bayesian-inversion/9158)
**Author:** [@GuillaumeGru](https://uqworld.org/u/GuillaumeGru)\ **Replies:** 5\ **Last updated:** [February 26, 2026, 3:31pm UTC](https://uqworld.org/t/momap-definition-for-multiple-models-with-multidimensional-outputs-uq-py-lab-bayesian-inversion/9158 "2026-02-26T15:31:14Z")
Dear UQWorld community, I am trying to use the Bayesian inversion module of UQ\[py\]Lab to solve an inverse problem based on synthetic data. I will describe briefly the error I encounter and then try to be as precise as … --- ## [\[Sensitivity analysis with two parameters\] Crash when computing the second order in uq\_print\_uq\_sensitivity](https://uqworld.org/t/sensitivity-analysis-with-two-parameters-crash-when-computing-the-second-order-in-uq-print-uq-sensitivity/9137)
**Author:** [@MarcLambert](https://uqworld.org/u/MarcLambert)\ **Replies:** 1\ **Last updated:** [February 11, 2026, 11:07am UTC](https://uqworld.org/t/sensitivity-analysis-with-two-parameters-crash-when-computing-the-second-order-in-uq-print-uq-sensitivity/9137 "2026-02-11T11:07:16Z")
Dear all When using UQLab for a sensitivity analysis of a function of two parameters the computation crashes when plotting the second order Sobol index in subroutine uq\_print\_uq\_sensitivity.m with the following error : … --- ## [Using UQLab with the Life Cycle Assessment Methodology](https://uqworld.org/t/using-uqlab-with-the-life-cycle-assessment-methodology/9151)
**Author:** [@aamartins](https://uqworld.org/u/aamartins)\ **Replies:** 0\ **Last updated:** [December 23, 2025, 7:20pm UTC](https://uqworld.org/t/using-uqlab-with-the-life-cycle-assessment-methodology/9151 "2025-12-23T19:20:21Z")
Hi all, I am a researcher in LCA and sustainability assessmente, where uncertainty analysis has become standard. Do anyone has experience with using UQLab with LCA? Regards, António Martins --- ## [Comparison between Leave-One-Out Cross-Validation errors](https://uqworld.org/t/comparison-between-leave-one-out-cross-validation-errors/9138)
**Author:** [@SimoneRomani12](https://uqworld.org/u/SimoneRomani12)\ **Replies:** 1\ **Last updated:** [December 11, 2025, 7:18am UTC](https://uqworld.org/t/comparison-between-leave-one-out-cross-validation-errors/9138 "2025-12-11T07:18:43Z")
Dear all, I would like to ask you one opinion about the Leave-One-Out Cross-validation error. Specifically, I have determined a Non-Intrusive Polynomial Chaos Expansion for two different “Outputs of interest” (I have us… --- ## [How to start performing Reliability analysis with UQLab using MATLA B](https://uqworld.org/t/how-to-start-performing-reliability-analysis-with-uqlab-using-matla-b/9131)
**Author:** [@Muazu](https://uqworld.org/u/Muazu)\ **Replies:** 0\ **Last updated:** [November 23, 2025, 6:29pm UTC](https://uqworld.org/t/how-to-start-performing-reliability-analysis-with-uqlab-using-matla-b/9131 "2025-11-23T18:29:52Z")
Dear All. I am highly excited to join this community. Please, I am conducting research that involves reliability analysis, and I am considering using UQLab with MATLAB for the analysis. I have connected UQLab with MATL… --- ## [How to do Sobol sensitivity analysis for existing datasets](https://uqworld.org/t/how-to-do-sobol-sensitivity-analysis-for-existing-datasets/4054)
**Author:** [@saeid\_saberi](https://uqworld.org/u/saeid_saberi)\ **Replies:** 3\ **Last updated:** [October 29, 2025, 6:01pm UTC](https://uqworld.org/t/how-to-do-sobol-sensitivity-analysis-for-existing-datasets/4054 "2025-10-29T18:01:38Z")
I’ve extracted datasets from experiments and want to perform a sensitivity analysis using UQLab. However, I couldn’t find any documentation on how to directly apply sensitivity analysis to raw data. From what I’ve seen, … --- ## [UQ Book Review Request](https://uqworld.org/t/uq-book-review-request/9118)
**Author:** [@Elias](https://uqworld.org/u/Elias)\ **Replies:** 0\ **Last updated:** [October 24, 2025, 7:59am UTC](https://uqworld.org/t/uq-book-review-request/9118 "2025-10-24T07:59:09Z")
Hello everyone, I have been reading “C. Soize, 2017, Uncertainty Quantification - An accelerated course with advanced applications in computational engineering, 1 ed., Cham: Springer. “, I’d be interested to hear from a… --- ## [Multiple Point Enrichment in ALR: learning function based stopping criterion](https://uqworld.org/t/multiple-point-enrichment-in-alr-learning-function-based-stopping-criterion/9102)
**Author:** [@colette.buchs](https://uqworld.org/u/colette.buchs)\ **Replies:** 0\ **Last updated:** [October 15, 2025, 11:38am UTC](https://uqworld.org/t/multiple-point-enrichment-in-alr-learning-function-based-stopping-criterion/9102 "2025-10-15T11:38:56Z")
Dear all, I am working on integrating active learning reliability in ZSoil. For now, it worked really well. Thanks for your great work! For multiple reasons, we would like to use multiple point enrichment combined with… --- ## [Error when using uq\_evalStochSimMetrics with SPCE model](https://uqworld.org/t/error-when-using-uq-evalstochsimmetrics-with-spce-model/9081)
**Author:** [@HZhang](https://uqworld.org/u/HZhang)\ **Replies:** 0\ **Last updated:** [October 12, 2025, 8:02pm UTC](https://uqworld.org/t/error-when-using-uq-evalstochsimmetrics-with-spce-model/9081 "2025-10-12T20:02:52Z")
Hi, I am encountering the following errors when using the “uq\_evalStochSimMetrics” function to get the metrics of an SPCE model: Error using uq\_eval\_univ\_basis (line 46) Index in position 1 exceeds array bounds. Inde… --- ## [KLE Random Field and PCE metamodel](https://uqworld.org/t/kle-random-field-and-pce-metamodel/9057)
**Author:** [@Jacek\_Swiegoda](https://uqworld.org/u/Jacek_Swiegoda)\ **Replies:** 0\ **Last updated:** [October 9, 2025, 4:23pm UTC](https://uqworld.org/t/kle-random-field-and-pce-metamodel/9057 "2025-10-09T16:23:48Z")
Hello everyone, I am trying to perform probabilistic computations for a FEM model involving KLE random fields. In my analysis, I would like to build a metamodel based on Polynomial Chaos Expansion (PCE) using UQpyLab. T… --- ## [Why can't we use arbitrary polynomials to solve problems with negative inputs?](https://uqworld.org/t/why-cant-we-use-arbitrary-polynomials-to-solve-problems-with-negative-inputs/4056)
**Author:** [@LJY](https://uqworld.org/u/LJY)\ **Replies:** 4\ **Last updated:** [October 9, 2025, 9:26am UTC](https://uqworld.org/t/why-cant-we-use-arbitrary-polynomials-to-solve-problems-with-negative-inputs/4056 "2025-10-09T09:26:02Z")
I am dealing with a 21-dimensional uncertain input problem. The inputs are all Gaussian distributed, and one of them is a negative number. I used the LARS method to expand it into a chaotic polynomial. When it is expande… --- ## [Why is my uqlab PCE output constant? (For pre-existing discrete data)](https://uqworld.org/t/why-is-my-uqlab-pce-output-constant-for-pre-existing-discrete-data/4074)
**Author:** [@AverySeeley](https://uqworld.org/u/AverySeeley)\ **Replies:** 1\ **Last updated:** [October 2, 2025, 8:47am UTC](https://uqworld.org/t/why-is-my-uqlab-pce-output-constant-for-pre-existing-discrete-data/4074 "2025-10-02T08:47:37Z")
I am trying to create a PCE model from pre-existing discrete data. I have one input variable (Xtrain) and one output variable (Ytrain), both discrete. I have created a Kernel Density Estimation to make it continuous for … --- ## [ANCOVA Error: problem dimension undefined](https://uqworld.org/t/ancova-error-problem-dimension-undefined/4075)
**Author:** [@Xin-Yue\_Wang](https://uqworld.org/u/Xin-Yue_Wang)\ **Replies:** 5\ **Last updated:** [October 1, 2025, 5:13pm UTC](https://uqworld.org/t/ancova-error-problem-dimension-undefined/4075 "2025-10-01T17:13:00Z")
Hi there, I’m using UQ\[py\]Lab for sensitivity analysis. Below please find a summary of the problem statement: Number of input variables: 30 Number of output: 1 Sample size: 7600 I have obtained the data for input vari… --- ## [SPCE with active learning](https://uqworld.org/t/spce-with-active-learning/8950)
**Author:** [@HZhang](https://uqworld.org/u/HZhang)\ **Replies:** 0\ **Last updated:** [September 30, 2025, 3:45pm UTC](https://uqworld.org/t/spce-with-active-learning/8950 "2025-09-30T15:45:34Z")
Hi Everyone, I’m interested in how the active learning algorithm for SPCE described in the following paper could be implemented in UQLab: https://doi.org/10.48550/arXiv.2507.04553 I’d greatly appreciate any… --- ## [Problem, if burnIn is an integer value](https://uqworld.org/t/problem-if-burnin-is-an-integer-value/7819)
**Author:** [@abhi\_sac](https://uqworld.org/u/abhi_sac)\ **Replies:** 1\ **Last updated:** [September 4, 2025, 6:52am UTC](https://uqworld.org/t/problem-if-burnin-is-an-integer-value/7819 "2025-09-04T06:52:19Z")
I believe I have identified an inconsistency between the Bayesian inversion manual and the implementation in uq\_postProcessInversion.m when the function is called with an integer value for the burnIn parameter. Denoting … --- ## [Sample based Kucherenko index results in total effect of 1 for large size of input variables (n \> 11)](https://uqworld.org/t/sample-based-kucherenko-index-results-in-total-effect-of-1-for-large-size-of-input-variables-n-11/3858)
**Author:** [@DHeiden](https://uqworld.org/u/DHeiden)\ **Replies:** 3\ **Last updated:** [August 27, 2025, 1:45pm UTC](https://uqworld.org/t/sample-based-kucherenko-index-results-in-total-effect-of-1-for-large-size-of-input-variables-n-11/3858 "2025-08-27T13:45:22Z")
Hello, I wanted to calculate sample based kucherenko indices. Sample size = 36000. I recognised that the total effect is always 1 if the sample consists of more than 11 input variables. I recognised that this is due to … --- ## [How to define my probabilistic input distributions?](https://uqworld.org/t/how-to-define-my-probabilistic-input-distributions/131)
**Author:** [@bsudret](https://uqworld.org/u/bsudret)\ **Replies:** 2\ **Last updated:** [July 14, 2025, 4:57pm UTC](https://uqworld.org/t/how-to-define-my-probabilistic-input-distributions/131 "2025-07-14T16:57:13Z")
Introduction A key step in an uncertainty quantification (UQ) study is to define the distributions that will be used to represent the uncertainty in the input parameters of a computational model of interest. Referring to… --- ## [Error in Multi-Objective RBDO with UQLab](https://uqworld.org/t/error-in-multi-objective-rbdo-with-uqlab/4072)
**Author:** [@pouya\_zrbipour](https://uqworld.org/u/pouya_zrbipour)\ **Replies:** 1\ **Last updated:** [July 10, 2025, 2:37pm UTC](https://uqworld.org/t/error-in-multi-objective-rbdo-with-uqlab/4072 "2025-07-10T14:37:14Z")
Dear UQWorld Community, I am facing an error saying “Undefined function or variable ‘myInput’” when I run my Multi-objective reliability-based design optimization uq\_Ex08\_BermBreakwater\_constraint.m (1.1 KB) uq\_Ex08\_B… [Next page](https://uqworld.org/latest.md?page=1)