# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=404

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**Page:** 405

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## [Flux Zygote Gradient: Understanding Mutating arrays is not supported](https://discourse.julialang.org/t/flux-zygote-gradient-understanding-mutating-arrays-is-not-supported/46324)

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**Author:** [@rakeshvar](https://discourse.julialang.org/u/rakeshvar)\
**Replies:** 21\
**Last updated:** [December 3, 2020, 5:21am UTC](https://discourse.julialang.org/t/flux-zygote-gradient-understanding-mutating-arrays-is-not-supported/46324 "2020-12-03T05:21:49Z")

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Namaste, I am trying to implement CTC loss in Flux/Zygote. And running into Error: Mutating arrays is not supported. So I cooked up the toy example below to gain better understanding. Given an input x, I perform some s…

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## [It there a way or package to solve the nonlinear mixed complementarity problem?](https://discourse.julialang.org/t/it-there-a-way-or-package-to-solve-the-nonlinear-mixed-complementarity-problem/51161)

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**Author:** [@jshengdb](https://discourse.julialang.org/u/jshengdb)\
**Replies:** 2\
**Last updated:** [December 3, 2020, 2:38am UTC](https://discourse.julialang.org/t/it-there-a-way-or-package-to-solve-the-nonlinear-mixed-complementarity-problem/51161 "2020-12-03T02:38:35Z")

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Hi Julia user: I was wondering if there was a way or package to model and solver the nonlinear mixed complementarity problem? I know now we can model the linear complementarity problem by using complement constraints in…

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## [How to use \`in\` with @where \[DataFramesMeta\]?](https://discourse.julialang.org/t/how-to-use-in-with-where-dataframesmeta/2176)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 6\
**Last updated:** [December 3, 2020, 1:36am UTC](https://discourse.julialang.org/t/how-to-use-in-with-where-dataframesmeta/2176 "2020-12-03T01:36:07Z")

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As from the title, how to use in with @where (DataFramesMeta)? e.g. @where(df, :x in \["cat1", "cat2"\]) I did already try :x .in \["cat1", "cat2"\] or .in(:x, \["cat1", "cat2"\])…

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## [Rand/logpdf semantic consistency](https://discourse.julialang.org/t/rand-logpdf-semantic-consistency/50904)

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**Author:** [@cscherrer](https://discourse.julialang.org/u/cscherrer)\
**Replies:** 12\
**Last updated:** [December 3, 2020, 1:07am UTC](https://discourse.julialang.org/t/rand-logpdf-semantic-consistency/50904 "2020-12-03T01:07:54Z")

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There’s a subtle issue I’ve mentioned before involving rand and logpdf that has gotten in the way of composability. I’m thinking in terms of Soss and MeasureTheory.jl, but I thought I’d post here since it may be helpful …

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## [Constraining binary integer variables with indicator constraints](https://discourse.julialang.org/t/constraining-binary-integer-variables-with-indicator-constraints/51043)

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**Author:** [@bvilmann](https://discourse.julialang.org/u/bvilmann)\
**Replies:** 9\
**Last updated:** [December 2, 2020, 10:11pm UTC](https://discourse.julialang.org/t/constraining-binary-integer-variables-with-indicator-constraints/51043 "2020-12-02T22:11:15Z")

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I want to constrain binary integer variables, x, with indicator constraints to express a change in a binary integer variable over a specific iterator, t. I thought this could be nice since the different cases are obviou…

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## [Using Julia to solve the student final project allocation problem](https://discourse.julialang.org/t/using-julia-to-solve-the-student-final-project-allocation-problem/51019)

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**Author:** [@sui](https://discourse.julialang.org/u/sui)\
**Replies:** 7\
**Last updated:** [December 2, 2020, 8:56am UTC](https://discourse.julialang.org/t/using-julia-to-solve-the-student-final-project-allocation-problem/51019 "2020-12-02T08:56:26Z")

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I am doing a project that I have to use Julia code to solve a student’s final project allocation problem. I am kind of new to this kind of coding and new for Julia. I need some help with this. Start with the problem, I …

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## [How to prevent plot! from over-writing earlier saved plot](https://discourse.julialang.org/t/how-to-prevent-plot-from-over-writing-earlier-saved-plot/51072)

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**Author:** [@CosmoProf](https://discourse.julialang.org/u/CosmoProf)\
**Replies:** 2\
**Last updated:** [December 2, 2020, 3:40am UTC](https://discourse.julialang.org/t/how-to-prevent-plot-from-over-writing-earlier-saved-plot/51072 "2020-12-02T03:40:14Z")

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Hi, I’ve asked this as part of an earlier question, but no resolution yet. In my program, I have this contour plot extracted from data after many hours of execution, and I have to add new data on top of the contour plo…

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## [CoolProp fluid property database reinforces its availability for Julia users](https://discourse.julialang.org/t/coolprop-fluid-property-database-reinforces-its-availability-for-julia-users/1325)

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**Author:** [@DANA-Laboratory](https://discourse.julialang.org/u/DANA-Laboratory)\
**Replies:** 27\
**Last updated:** [December 2, 2020, 3:38am UTC](https://discourse.julialang.org/t/coolprop-fluid-property-database-reinforces-its-availability-for-julia-users/1325 "2020-12-02T03:38:03Z")

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CoolProp, Is an open-source, cross-platform, reference-quality fluid property database that mirrors many of the functionalities of REFPROP. The codebase is written in C++ and wrappers are available for Python and C#. A …

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## [Package to solve the Maxey-Riley equation with Basset history term](https://discourse.julialang.org/t/package-to-solve-the-maxey-riley-equation-with-basset-history-term/51079)

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**Author:** [@mleprovost](https://discourse.julialang.org/u/mleprovost)\
**Replies:** 0\
**Last updated:** [December 2, 2020, 2:44am UTC](https://discourse.julialang.org/t/package-to-solve-the-maxey-riley-equation-with-basset-history-term/51079 "2020-12-02T02:44:18Z")

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Hello, Is there a Julia package to solve the Maxey-Riley equation (equation (1) of this paper https://arxiv.org/pdf/1310.2450.pdf), that governs the motion of a small sphere immersed in a fluid. This equation is a secon…

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## [Local sensitivities via ForwardSensitivity from DifferentialEquations in optimization with AD](https://discourse.julialang.org/t/local-sensitivities-via-forwardsensitivity-from-differentialequations-in-optimization-with-ad/50286)

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**Author:** [@moesphere](https://discourse.julialang.org/u/moesphere)\
**Replies:** 2\
**Last updated:** [December 2, 2020, 1:47am UTC](https://discourse.julialang.org/t/local-sensitivities-via-forwardsensitivity-from-differentialequations-in-optimization-with-ad/50286 "2020-12-02T01:47:24Z")

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I am trying to optimize local sensitivities of an ode problem using ODEForwardSensitivityProblem from the DifferentialEquations suite, but the last line throws a TypeError. I am using forward sensitivites as the ode sys…

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## [Can Julia efficiently make use of 20+ cores for transforming hundreds of millions of rows for machine learning?](https://discourse.julialang.org/t/can-julia-efficiently-make-use-of-20-cores-for-transforming-hundreds-of-millions-of-rows-for-machine-learning/50968)

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**Author:** [@Kevin\_Shen](https://discourse.julialang.org/u/Kevin_Shen)\
**Replies:** 27\
**Last updated:** [December 1, 2020, 3:15pm UTC](https://discourse.julialang.org/t/can-julia-efficiently-make-use-of-20-cores-for-transforming-hundreds-of-millions-of-rows-for-machine-learning/50968 "2020-12-01T15:15:30Z")

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I’ve seen similar questions posted but I wanted to ask my question to see if I can get more precise answers. I train machine learning models on datasets with hundreds of millions of rows (10^8). On this order of magnitu…

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## [Get eigenvectors of non-normal, defective matrices in julia](https://discourse.julialang.org/t/get-eigenvectors-of-non-normal-defective-matrices-in-julia/50871)

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**Author:** [@volkerkarle](https://discourse.julialang.org/u/volkerkarle)\
**Replies:** 7\
**Last updated:** [December 1, 2020, 2:11pm UTC](https://discourse.julialang.org/t/get-eigenvectors-of-non-normal-defective-matrices-in-julia/50871 "2020-12-01T14:11:07Z")

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Dear community, Given a non-normal defective matrix, how can I get all eigenvectors of this matrix? An obvious way would be to use the jordan normal form. I wonder if somebody already calculated the jordan normal form …

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## [How to find inflection point of curve?](https://discourse.julialang.org/t/how-to-find-inflection-point-of-curve/50892)

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**Author:** [@Luigi\_Marongiu](https://discourse.julialang.org/u/Luigi_Marongiu)\
**Replies:** 20\
**Last updated:** [November 30, 2020, 7:56am UTC](https://discourse.julialang.org/t/how-to-find-inflection-point-of-curve/50892 "2020-11-30T07:56:38Z")

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Hello, I have the function y = ϑ - ((1/ω) \* log(x/ε)) - 1/μ Is there a simple way in Julia to find the flection point of the function? if I set these paramaters: mu = 0.72 # maximum growth rate resistant (…

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## [Why do I get this error "UndefVarError: cov not defined"](https://discourse.julialang.org/t/why-do-i-get-this-error-undefvarerror-cov-not-defined/50239)

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**Author:** [@RaquelSantos](https://discourse.julialang.org/u/RaquelSantos)\
**Replies:** 16\
**Last updated:** [November 30, 2020, 6:42pm UTC](https://discourse.julialang.org/t/why-do-i-get-this-error-undefvarerror-cov-not-defined/50239 "2020-11-30T18:42:28Z")

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Could someone help me solve the error: UndefVarError: cov not defined of the test code taken from the site JuMPeR - Robust Optimization with JuMP — JuMPeR -- Julia for Mathematical Programming 0.0 documentation Did thi…

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## [Update "min" and "max" of Ranged Slider via "relayoutData" of Figure not working](https://discourse.julialang.org/t/update-min-and-max-of-ranged-slider-via-relayoutdata-of-figure-not-working/51037)

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**Author:** [@lambcount](https://discourse.julialang.org/u/lambcount)\
**Replies:** 0\
**Last updated:** [December 1, 2020, 10:12am UTC](https://discourse.julialang.org/t/update-min-and-max-of-ranged-slider-via-relayoutdata-of-figure-not-working/51037 "2020-12-01T10:12:06Z")

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Hi , i am quite new to Julia and especially Dash. So maybe there is an easy fix to my problems. I want to plot a heatmap and then add via callback vlines to the heatmap. That is working quite well. In another callback…

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## [Not sure how to generate ForwardDiff function](https://discourse.julialang.org/t/not-sure-how-to-generate-forwarddiff-function/51030)

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**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 1\
**Last updated:** [December 1, 2020, 6:01am UTC](https://discourse.julialang.org/t/not-sure-how-to-generate-forwarddiff-function/51030 "2020-12-01T06:01:21Z")

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I try to run this, but it says there is a format problem, I think with line 3 (fp(x)) using ForwardDiff f(x)=x^6-2 fp(x) = x-\>ForwardDiff.derivative(f, x) x=1.5 x=x-(f(x)/fp(x))

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## [BoundsError: attempt to access Float64 using ModelingToolkit.jl and AutoOptimize.jl to optimize a DifferentialEquations.jl model](https://discourse.julialang.org/t/boundserror-attempt-to-access-float64-using-modelingtoolkit-jl-and-autooptimize-jl-to-optimize-a-differentialequations-jl-model/51000)

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**Author:** [@claudio20497](https://discourse.julialang.org/u/claudio20497)\
**Replies:** 1\
**Last updated:** [December 1, 2020, 4:35am UTC](https://discourse.julialang.org/t/boundserror-attempt-to-access-float64-using-modelingtoolkit-jl-and-autooptimize-jl-to-optimize-a-differentialequations-jl-model/51000 "2020-12-01T04:35:19Z")

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Hello, I’m trying to optimize the code and finding the best solve algorithm for an epidemiological model. Anyway, I get an error that due to my inexperience I cannot solve. So below is a simplified verison of the model…

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## [Solving ODE based on experimental data (DifferentialEquations.jl)](https://discourse.julialang.org/t/solving-ode-based-on-experimental-data-differentialequations-jl/51002)

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**Author:** [@maajdl](https://discourse.julialang.org/u/maajdl)\
**Replies:** 4\
**Last updated:** [November 30, 2020, 9:09pm UTC](https://discourse.julialang.org/t/solving-ode-based-on-experimental-data-differentialequations-jl/51002 "2020-11-30T21:09:51Z")

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Hello, I am solving a simple ODE system with 5 state variables. It is essentially made of 5 coupled RC sytems with a few (current) excitations. These excitations are 6000 experimental data measured every 10 minutes. …

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## [Embed local image in Dash app with HTTP?](https://discourse.julialang.org/t/embed-local-image-in-dash-app-with-http/51004)

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**Author:** [@Iulian.Cioarca](https://discourse.julialang.org/u/Iulian.Cioarca)\
**Replies:** 3\
**Last updated:** [November 30, 2020, 7:19pm UTC](https://discourse.julialang.org/t/embed-local-image-in-dash-app-with-http/51004 "2020-11-30T19:19:14Z")

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I am developing a Dash.jl app and discovered that I cannot embed local pictures. One workaround I found is to somehow host images on a local server in order to display them, but I have no idea how to do that in Julia. M…

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## [Partitioning Around Medoids (PAM) in Julia](https://discourse.julialang.org/t/partitioning-around-medoids-pam-in-julia/50879)

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**Author:** [@mthelm85](https://discourse.julialang.org/u/mthelm85)\
**Replies:** 10\
**Last updated:** [November 30, 2020, 4:45pm UTC](https://discourse.julialang.org/t/partitioning-around-medoids-pam-in-julia/50879 "2020-11-30T16:45:20Z")

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I’m unable to find any package that implements this algorithm. I’m going to attempt to implement the algorithm myself but I’m not sure if I have the know-how to get it over the finish line, to be perfectly honest. Would …

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## [Best way to learn differentiable computing?](https://discourse.julialang.org/t/best-way-to-learn-differentiable-computing/50955)

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**Author:** [@StatisticalMouse](https://discourse.julialang.org/u/StatisticalMouse)\
**Replies:** 1\
**Last updated:** [November 30, 2020, 3:52pm UTC](https://discourse.julialang.org/t/best-way-to-learn-differentiable-computing/50955 "2020-11-30T15:52:28Z")

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What would be the best resource to get started? Also, what would be the ‘state of the art’ in this area right now?

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## [\[ANN\] PubChemCrawler](https://discourse.julialang.org/t/ann-pubchemcrawler/50935)

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**Author:** [@tim.holy](https://discourse.julialang.org/u/tim.holy)\
**Replies:** 0\
**Last updated:** [November 29, 2020, 2:03pm UTC](https://discourse.julialang.org/t/ann-pubchemcrawler/50935 "2020-11-29T14:03:17Z")

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For the chemistry- or cheminformatics-inclined among you, you may be interested in PubChemCrawler, which makes it easier to query the PubChem service. https://github.com/JuliaHealth/PubChemCrawler.jl

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## [Optim, Forward Differentiation and OnceDifferentiable with MLE](https://discourse.julialang.org/t/optim-forward-differentiation-and-oncedifferentiable-with-mle/16320)

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**Author:** [@cosmia](https://discourse.julialang.org/u/cosmia)\
**Replies:** 18\
**Last updated:** [November 28, 2020, 8:52pm UTC](https://discourse.julialang.org/t/optim-forward-differentiation-and-oncedifferentiable-with-mle/16320 "2020-11-28T20:52:36Z")

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Hi guys, I am estimating a model by Maximum Likelihood. So far, I’ve been using Nelder-Mead as the optimization method where I don’t need to provide any gradient or Hessian. Convergence has been somewhat slow, and I usu…

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## [Gaussian Process Model with Turing](https://discourse.julialang.org/t/gaussian-process-model-with-turing/42453)

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**Author:** [@kevbonham](https://discourse.julialang.org/u/kevbonham)\
**Replies:** 84\
**Last updated:** [November 28, 2020, 6:12pm UTC](https://discourse.julialang.org/t/gaussian-process-model-with-turing/42453 "2020-11-28T18:12:19Z")

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Is it possible to specifiy a Gaussian process (GP) regression model directly in Turing? I’ve looked at Stheno.jl and GaussianProcesses.jl, but neither have an obvious way to specify a multivariate model (GaussianProcesse…

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## [Network application framework in Julia (i.e. netty, NIO, MINA)](https://discourse.julialang.org/t/network-application-framework-in-julia-i-e-netty-nio-mina/50889)

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**Author:** [@mks](https://discourse.julialang.org/u/mks)\
**Replies:** 0\
**Last updated:** [November 28, 2020, 6:24am UTC](https://discourse.julialang.org/t/network-application-framework-in-julia-i-e-netty-nio-mina/50889 "2020-11-28T06:24:19Z")

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Hello, is there work going on to come up with a network application framework in Julia like netty, NIO, MINA? https://netty.io/ It would be nice to be able to use gRPC and Protobuf. I know there is protobuf.jl which …

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## [Error while using ModelingToolkit](https://discourse.julialang.org/t/error-while-using-modelingtoolkit/50881)

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**Author:** [@contradict](https://discourse.julialang.org/u/contradict)\
**Replies:** 2\
**Last updated:** [November 28, 2020, 4:11am UTC](https://discourse.julialang.org/t/error-while-using-modelingtoolkit/50881 "2020-11-28T04:11:58Z")

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I am building a model of a pneumatic system with ModelingToolkit and have gotten stuck. I have a not-very-minimal example of the error in this gist. I haven’t been able to trim it down any more and preserve the error. H…

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## [Plotting differential equations solutions with varying color](https://discourse.julialang.org/t/plotting-differential-equations-solutions-with-varying-color/50884)

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**Author:** [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)\
**Replies:** 1\
**Last updated:** [November 28, 2020, 4:00am UTC](https://discourse.julialang.org/t/plotting-differential-equations-solutions-with-varying-color/50884 "2020-11-28T04:00:41Z")

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When plotting DifferentialEquations solutions, the plotdensity keyword does not seem to work together with line\_z. See code below where data interpolation within Plots does not take place, when we color the solution by t…

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## [How to get components of vector solution in Gridap](https://discourse.julialang.org/t/how-to-get-components-of-vector-solution-in-gridap/50882)

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**Author:** [@jmura](https://discourse.julialang.org/u/jmura)\
**Replies:** 0\
**Last updated:** [November 27, 2020, 11:43pm UTC](https://discourse.julialang.org/t/how-to-get-components-of-vector-solution-in-gridap/50882 "2020-11-27T23:43:25Z")

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Dear Julia users, I’m using Gridap, and I’m learning from the tutorials. I have some questions: a) How can we recover x- or y-components from a numerical solution uh, as the solution to linear elasticity (like in the t…

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## [K-Medoids in Julia - Results Quality](https://discourse.julialang.org/t/k-medoids-in-julia-results-quality/50687)

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**Author:** [@mthelm85](https://discourse.julialang.org/u/mthelm85)\
**Replies:** 7\
**Last updated:** [November 27, 2020, 9:54pm UTC](https://discourse.julialang.org/t/k-medoids-in-julia-results-quality/50687 "2020-11-27T21:54:05Z")

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I was reading the Wikipedia page on k-medoids clustering and in the Software section, it’s stated that: Julia contains a k-medoid implementation of the k-means style algorithm (faster, but much worse result quality) i…

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## [Repeatedly calculating likelihood using Turing](https://discourse.julialang.org/t/repeatedly-calculating-likelihood-using-turing/50608)

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**Author:** [@ArnoStrouwen](https://discourse.julialang.org/u/ArnoStrouwen)\
**Replies:** 2\
**Last updated:** [November 27, 2020, 8:56pm UTC](https://discourse.julialang.org/t/repeatedly-calculating-likelihood-using-turing/50608 "2020-11-27T20:56:36Z")

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I want to repeatedly calculate likelihoods of the same Turing model at different parameter values, and also with different possible observations. What is the best way to do this in Turing? A minimal example of the type o…

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