# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=41

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**Page:** 42

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## [Plot ellipse in Makie?](https://discourse.julialang.org/t/plot-ellipse-in-makie/82814)

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**Author:** [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Replies:** 5\
**Last updated:** [May 27, 2025, 4:44pm UTC](https://discourse.julialang.org/t/plot-ellipse-in-makie/82814 "2025-05-27T16:44:24Z")

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How can I draw a 2-dimensional ellipse in a Makie plot?

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## [Basic Data Utilities in PowerModels.jl---some more methods?](https://discourse.julialang.org/t/basic-data-utilities-in-powermodels-jl-some-more-methods/129291)

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**Author:** [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Replies:** 9\
**Last updated:** [May 27, 2025, 2:28pm UTC](https://discourse.julialang.org/t/basic-data-utilities-in-powermodels-jl-some-more-methods/129291 "2025-05-27T14:28:38Z")

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This post is a feature request related to Basic Data Utilities · PowerModels. Although this sparse incidence matrix (denoted A) is useful, sometimes we may need another more succinct matrix—I call it bft, branch\_from\_to…

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## [How can I generate a 3D annulus surface and mesh it using Meshes.jl?](https://discourse.julialang.org/t/how-can-i-generate-a-3d-annulus-surface-and-mesh-it-using-meshes-jl/110949)

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**Author:** [@xiaoming](https://discourse.julialang.org/u/xiaoming)\
**Replies:** 7\
**Last updated:** [May 27, 2025, 11:46am UTC](https://discourse.julialang.org/t/how-can-i-generate-a-3d-annulus-surface-and-mesh-it-using-meshes-jl/110949 "2025-05-27T11:46:18Z")

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I have tried using PolyArea. Here is MME: ring1=Meshes.Ring(\[(cos(t),sin(t),0) for t in 0.1:0.1:2pi\]) ring2=Meshes.Ring(\[(2cos(t),2sin(t),0) for t in 0.1:0.1:2pi\]) annulus = PolyArea(\[ring2, ring1\]) discretize(annulus, …

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## [Deriving the Jacobians without MTK](https://discourse.julialang.org/t/deriving-the-jacobians-without-mtk/129203)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 1\
**Last updated:** [May 26, 2025, 7:58pm UTC](https://discourse.julialang.org/t/deriving-the-jacobians-without-mtk/129203 "2025-05-26T19:58:46Z")

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I have a nonlinear, numeric model. The model uses a non-linear solver internally. It has three inputs, one output and many parameters. How can I calculate the Jacobians of a linearized model? Can I use AutoFiniteDiff() …

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## [Ordering of unknowns(system) in MTK when array-valued variables are scalarized via structural\_simplify](https://discourse.julialang.org/t/ordering-of-unknowns-system-in-mtk-when-array-valued-variables-are-scalarized-via-structural-simplify/129358)

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**Author:** [@sass-jacob](https://discourse.julialang.org/u/sass-jacob)\
**Replies:** 3\
**Last updated:** [May 26, 2025, 9:41pm UTC](https://discourse.julialang.org/t/ordering-of-unknowns-system-in-mtk-when-array-valued-variables-are-scalarized-via-structural-simplify/129358 "2025-05-26T21:41:01Z")

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What is the current rule for ordering of array-valued variables once structural\_simplify has been called and sort\_eqs is set to false? My current array has something like this: unknowns(sys)\[221:230\] (Φ\_s\_c(t))\[2\] (Φ…

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## [UpperTriangular arrays in RecursiveArrayTools](https://discourse.julialang.org/t/uppertriangular-arrays-in-recursivearraytools/129352)

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**Author:** [@Menno](https://discourse.julialang.org/u/Menno)\
**Replies:** 1\
**Last updated:** [May 26, 2025, 6:32pm UTC](https://discourse.julialang.org/t/uppertriangular-arrays-in-recursivearraytools/129352 "2025-05-26T18:32:15Z")

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Hi all, In the (otherwise absolutely wonderful) RecursiveArrayTools package, I’m fairly sure it must be possible to use UpperTriangular or LowerTriangular arrays as parts of an ArrayPartition. The source code (Recursive…

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## [Enzyme.jl Critical Issues with Basic Arithmetic Operations in Automatic Differentiation](https://discourse.julialang.org/t/enzyme-jl-critical-issues-with-basic-arithmetic-operations-in-automatic-differentiation/129216)

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**Author:** [@mra](https://discourse.julialang.org/u/mra)\
**Replies:** 7\
**Last updated:** [May 26, 2025, 12:59pm UTC](https://discourse.julialang.org/t/enzyme-jl-critical-issues-with-basic-arithmetic-operations-in-automatic-differentiation/129216 "2025-05-26T12:59:59Z")

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According to the Enzyme.jl documentation the “Enzyme differentiates arbitrary multivariate vector functions as the most general case in automatic differentiation”, however I encountered critical errors (including the ker…

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## [Problem with upper absorbing boundary with MethodOfLines.jl](https://discourse.julialang.org/t/problem-with-upper-absorbing-boundary-with-methodoflines-jl/129333)

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**Author:** [@sdwfrost](https://discourse.julialang.org/u/sdwfrost)\
**Replies:** 1\
**Last updated:** [May 26, 2025, 10:16am UTC](https://discourse.julialang.org/t/problem-with-upper-absorbing-boundary-with-methodoflines-jl/129333 "2025-05-26T10:16:41Z")

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Hi everyone, the following code runs, but my system leaks mass, due to the upper boundary - N should be constant. using ModelingToolkit using DifferentialEquations using MethodOfLines using DomainSets using Plots @para…

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## [Training a Neural ODE system using the output of a Method-Of-Lines computation](https://discourse.julialang.org/t/training-a-neural-ode-system-using-the-output-of-a-method-of-lines-computation/129313)

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**Author:** [@Rajat\_Shirali](https://discourse.julialang.org/u/Rajat_Shirali)\
**Replies:** 2\
**Last updated:** [May 26, 2025, 9:51am UTC](https://discourse.julialang.org/t/training-a-neural-ode-system-using-the-output-of-a-method-of-lines-computation/129313 "2025-05-26T09:51:53Z")

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Hello everyone! I’m currently looking to develop my own customised Julia code for training Neural ODEs using a Physics-Informed approach. I want to create an interactive PDE-based model; however, there are two constraint…

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## [Lack of conexionist NN package?](https://discourse.julialang.org/t/lack-of-conexionist-nn-package/129304)

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**Author:** [@PepeRoConde](https://discourse.julialang.org/u/PepeRoConde)\
**Replies:** 1\
**Last updated:** [May 25, 2025, 9:48am UTC](https://discourse.julialang.org/t/lack-of-conexionist-nn-package/129304 "2025-05-25T09:48:58Z")

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I found SOM.jl, NetworkDynamics.jl and Boltzmann.jl to be alone of other packages but not together between themselves. Wouldn’t it be nice a Conexionist Neural Networks pacake? or it be more appropiate to add those into …

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## [NLOPT constraint violation](https://discourse.julialang.org/t/nlopt-constraint-violation/128851)

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**Author:** [@mary](https://discourse.julialang.org/u/mary)\
**Replies:** 6\
**Last updated:** [May 24, 2025, 9:11pm UTC](https://discourse.julialang.org/t/nlopt-constraint-violation/128851 "2025-05-24T21:11:49Z")

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Hi I am using NLOP for topology optimization. First I did the deterministic topology optimization with constraint on volume, Now I am adding another constraint. As I checked the values for constraint it seems that the d…

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## [How to turn off the warn from PowerModels.jl](https://discourse.julialang.org/t/how-to-turn-off-the-warn-from-powermodels-jl/129289)

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**Author:** [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Replies:** 2\
**Last updated:** [May 24, 2025, 8:44am UTC](https://discourse.julialang.org/t/how-to-turn-off-the-warn-from-powermodels-jl/129289 "2025-05-24T08:44:33Z")

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julia\> import PowerModels julia\> PowerModels.make\_basic\_network(PowerModels.parse\_file("data/case118.m")); \[warn | PowerModels\]: this code only supports angmin values in -90 deg. to 90 deg., tightening the value on bran…

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## [Julia vs C++ for computational mechanics - Implicit Material Point Method](https://discourse.julialang.org/t/julia-vs-c-for-computational-mechanics-implicit-material-point-method/129180)

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**Author:** [@jowsky](https://discourse.julialang.org/u/jowsky)\
**Replies:** 13\
**Last updated:** [May 24, 2025, 5:20am UTC](https://discourse.julialang.org/t/julia-vs-c-for-computational-mechanics-implicit-material-point-method/129180 "2025-05-24T05:20:30Z")

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TL;DR : Writing an implicit Material Point Method solver. Would it be that much slower in Julia than C++ for a similar time-effort ? Hello, I am PhD student working on simulating creeping snow. I am currently planning …

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## [Problems porting discretization from MethodOfLines.jl to NeuralPDE.jl](https://discourse.julialang.org/t/problems-porting-discretization-from-methodoflines-jl-to-neuralpde-jl/129288)

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**Author:** [@sdwfrost](https://discourse.julialang.org/u/sdwfrost)\
**Replies:** 1\
**Last updated:** [May 24, 2025, 12:18am UTC](https://discourse.julialang.org/t/problems-porting-discretization-from-methodoflines-jl-to-neuralpde-jl/129288 "2025-05-24T00:18:01Z")

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Hi All, I’m trying to discretize a PDE with an integral term using NeuralPDE.jl. The problem discretizes fine with MethodOfLines.jl, but I get an error with NeuralPDE. The code is below - any suggestions? using Modelin…

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## [Enzyme reverse mode not working](https://discourse.julialang.org/t/enzyme-reverse-mode-not-working/129281)

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**Author:** [@miguelborrero](https://discourse.julialang.org/u/miguelborrero)\
**Replies:** 4\
**Last updated:** [May 23, 2025, 7:08pm UTC](https://discourse.julialang.org/t/enzyme-reverse-mode-not-working/129281 "2025-05-23T19:08:52Z")

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Hi there, I am struggling to get Enzyme working on a simplified version of my simulation. Here I give the code I’m running along with the error. My data is stored in an array of Student structs: using Enzyme using Sp…

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## [Flux PINN 1D Burgers](https://discourse.julialang.org/t/flux-pinn-1d-burgers/93262)

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**Author:** [@parf](https://discourse.julialang.org/u/parf)\
**Replies:** 11\
**Last updated:** [May 23, 2025, 4:54pm UTC](https://discourse.julialang.org/t/flux-pinn-1d-burgers/93262 "2025-05-23T16:54:32Z")

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Hi! I am trying to construct PINN to solve 1D Burgers equation in Flux.jl without using NeuralPDE.jl. The velocity field u(t,x) is defined by the net\_u(\[t,x\]) and the batch for training consists of N\_u=32 points correspo…

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## [DifferentialEquations.jl: LU factor ( M + dt \* K ) once prior to time-stepping loop](https://discourse.julialang.org/t/differentialequations-jl-lu-factor-m-dt-k-once-prior-to-time-stepping-loop/129255)

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**Author:** [@ziolai](https://discourse.julialang.org/u/ziolai)\
**Replies:** 3\
**Last updated:** [May 23, 2025, 11:38am UTC](https://discourse.julialang.org/t/differentialequations-jl-lu-factor-m-dt-k-once-prior-to-time-stepping-loop/129255 "2025-05-23T11:38:18Z")

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Can once trick DifferentialEquations.jl to LU factor M + dt \* K once only prior to the time stepping loop? Thx.

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## [Open multiple plots in REPL](https://discourse.julialang.org/t/open-multiple-plots-in-repl/129269)

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**Author:** [@CaG21](https://discourse.julialang.org/u/CaG21)\
**Replies:** 2\
**Last updated:** [May 23, 2025, 9:56am UTC](https://discourse.julialang.org/t/open-multiple-plots-in-repl/129269 "2025-05-23T09:56:25Z")

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I am trying to generate several plots while working in the REPL, that must be displayed individually (i.e., a new window for each plot). When I am trying to do so, however, each new plot replaces the old plot in the same…

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## [JuMP and SparseArrays](https://discourse.julialang.org/t/jump-and-sparsearrays/129264)

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**Author:** [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Replies:** 5\
**Last updated:** [May 23, 2025, 8:32am UTC](https://discourse.julialang.org/t/jump-and-sparsearrays/129264 "2025-05-23T08:32:57Z")

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The background is using SparseArrays, JuMP m = Model(); @variable(m, x\[1:2\]); My question is, can I create a sparse 2-by-2 object (whatever it is) denoted A, such that A\[1, 1\] returns me x\[1\], A\[2, 1\] returns me x\[2\].…

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## [Retrieve the simplex tableau from Gurobi.jl using JuMP](https://discourse.julialang.org/t/retrieve-the-simplex-tableau-from-gurobi-jl-using-jump/129237)

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**Author:** [@YANG-Hanbin](https://discourse.julialang.org/u/YANG-Hanbin)\
**Replies:** 3\
**Last updated:** [May 22, 2025, 11:42pm UTC](https://discourse.julialang.org/t/retrieve-the-simplex-tableau-from-gurobi-jl-using-jump/129237 "2025-05-22T23:42:36Z")

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Hello everyone! I’m trying to retrieve the optimal simplex tableau after solving a linear program using Gurobi. Thanks to Oscar’s help, I learned how to use the GRBBinvRowi function to access individual rows of the inve…

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## [How to get the dual of a non convex MIQCP Gurobi](https://discourse.julialang.org/t/how-to-get-the-dual-of-a-non-convex-miqcp-gurobi/129257)

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**Author:** [@manoj.centura](https://discourse.julialang.org/u/manoj.centura)\
**Replies:** 1\
**Last updated:** [May 22, 2025, 11:37pm UTC](https://discourse.julialang.org/t/how-to-get-the-dual-of-a-non-convex-miqcp-gurobi/129257 "2025-05-22T23:37:07Z")

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hi All, I need to get the duals of a nonconvex MIQCP i tried below code from model = Model(Gurobi.Optimizer) set\_optimizer\_attribute(model, "NonConvex", 2) @variable(model, x, Bin) @variable(model, y \>= 0) @constraint…

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## [ODE model with preallocated MVectors and still compatible with AD/stiff solvers?](https://discourse.julialang.org/t/ode-model-with-preallocated-mvectors-and-still-compatible-with-ad-stiff-solvers/129253)

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**Author:** [@Michael\_Barmann](https://discourse.julialang.org/u/Michael_Barmann)\
**Replies:** 2\
**Last updated:** [May 22, 2025, 8:48pm UTC](https://discourse.julialang.org/t/ode-model-with-preallocated-mvectors-and-still-compatible-with-ad-stiff-solvers/129253 "2025-05-22T20:48:50Z")

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I am writing an ODE model that describes the positions of a system of N interacting particles living in a 2D box. My ODE state vector u is an N x 2 array of numbers. Each call to the model updates a pre-allocated N x 2 a…

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## [Weird behavior of Keyboard events under Gtk4 on Linux](https://discourse.julialang.org/t/weird-behavior-of-keyboard-events-under-gtk4-on-linux/129219)

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**Author:** [@mwlidar](https://discourse.julialang.org/u/mwlidar)\
**Replies:** 1\
**Last updated:** [May 22, 2025, 7:37am UTC](https://discourse.julialang.org/t/weird-behavior-of-keyboard-events-under-gtk4-on-linux/129219 "2025-05-22T07:37:08Z")

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After testing my application on a Linux system I get some strange behavior of keyboard events. Here is a MWE to illustrate it: win = GtkWindow("Key Test", 300, 300) eck = GtkEventControllerKey(win) signal\_c…

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## [Help training a NN that's used as a parameter in an ODE](https://discourse.julialang.org/t/help-training-a-nn-thats-used-as-a-parameter-in-an-ode/129231)

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**Author:** [@alexl123](https://discourse.julialang.org/u/alexl123)\
**Replies:** 1\
**Last updated:** [May 22, 2025, 2:01am UTC](https://discourse.julialang.org/t/help-training-a-nn-thats-used-as-a-parameter-in-an-ode/129231 "2025-05-22T02:01:42Z")

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Hello! I’ve been pulling my hair out trying to implement an ODE where one of the parameters is the output of a NN net. ChatGPT has me going in circles. Depending on what fixes I try I either get a: Error in epoch 1: Me…

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## [What does the network constraint look like in the capacity expansion problem](https://discourse.julialang.org/t/what-does-the-network-constraint-look-like-in-the-capacity-expansion-problem/129214)

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**Author:** [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Replies:** 1\
**Last updated:** [May 21, 2025, 9:31pm UTC](https://discourse.julialang.org/t/what-does-the-network-constraint-look-like-in-the-capacity-expansion-problem/129214 "2025-05-21T21:31:31Z")

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I’m looking for help on the modeling issue of a power system capacity expansion problem. Here is a related tutorial Power Balance · GenX.jl. The z there is a “node” (electrical bus) quantity, and t there is an index of…

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## [AR(1) correlation structure on errors with MixedModels.jl](https://discourse.julialang.org/t/ar-1-correlation-structure-on-errors-with-mixedmodels-jl/128066)

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**Author:** [@slwu89](https://discourse.julialang.org/u/slwu89)\
**Replies:** 5\
**Last updated:** [May 21, 2025, 4:34pm UTC](https://discourse.julialang.org/t/ar-1-correlation-structure-on-errors-with-mixedmodels-jl/128066 "2025-05-21T16:34:07Z")

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Hi all, I’m looking at the MixedModels.jl package and I’m curious if it (or something similar in Julia) can fit the following type of model I used nlme to fit in R. The part I can’t figure out is if there is a simple way…

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## [Please explain LinearAlgebra.\_\_normalize!](https://discourse.julialang.org/t/please-explain-linearalgebra-normalize/128636)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 7\
**Last updated:** [May 21, 2025, 3:10pm UTC](https://discourse.julialang.org/t/please-explain-linearalgebra-normalize/128636 "2025-05-21T15:10:47Z")

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I am trying to understand LinearAlgebra.\_\_normalize!, quoted in full here: @inline function \_\_normalize!(a::AbstractArray, nrm) # The largest positive floating point number whose inverse is less than infinity δ …

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## [Multi-argument Jacobian and gradient](https://discourse.julialang.org/t/multi-argument-jacobian-and-gradient/129029)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 7\
**Last updated:** [May 21, 2025, 12:04pm UTC](https://discourse.julialang.org/t/multi-argument-jacobian-and-gradient/129029 "2025-05-21T12:04:31Z")

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I have a function that takes multiple arguments (all of them vectors), and I want to obtain the Jacobian in each parameter (or, similarly, the gradient if the function maps to \\mathbb{R}). Is it best to unpack/pack like…

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## [Grouped Bar Plots](https://discourse.julialang.org/t/grouped-bar-plots/129170)

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**Author:** [@chelseas](https://discourse.julialang.org/u/chelseas)\
**Replies:** 2\
**Last updated:** [May 21, 2025, 9:47am UTC](https://discourse.julialang.org/t/grouped-bar-plots/129170 "2025-05-21T09:47:39Z")

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How do I get my grouped bar plot bars to be next to each other and not on top of each other? code pulling data from dataframe: plot\_vio = bar( categorical(analysis.type), analysis.val, group = categorical(string.…

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## [Does Coluna supports sos2 with gurobi, is there a way to implement its](https://discourse.julialang.org/t/does-coluna-supports-sos2-with-gurobi-is-there-a-way-to-implement-its/129153)

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**Author:** [@manoj.centura](https://discourse.julialang.org/u/manoj.centura)\
**Replies:** 3\
**Last updated:** [May 20, 2025, 9:30pm UTC](https://discourse.julialang.org/t/does-coluna-supports-sos2-with-gurobi-is-there-a-way-to-implement-its/129153 "2025-05-20T21:30:51Z")

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coluna = optimizer\_with\_attributes( Coluna.Optimizer, "params" =\> Coluna.Params( solver = Co…

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