# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=210

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**Page:** 211

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## [Mathematical validity of using SDE solver schemes for custom NoiseProcess(es) in DifferentialEquations.jl](https://discourse.julialang.org/t/mathematical-validity-of-using-sde-solver-schemes-for-custom-noiseprocess-es-in-differentialequations-jl/95025)

<div class="topic-metadata">

**Author:** [@tom-plaa](https://discourse.julialang.org/u/tom-plaa)\
**Replies:** 4\
**Last updated:** [March 6, 2023, 1:01pm UTC](https://discourse.julialang.org/t/mathematical-validity-of-using-sde-solver-schemes-for-custom-noiseprocess-es-in-differentialequations-jl/95025 "2023-03-06T13:01:51Z")

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As we know, DifferentialEquations.jl has the amazing feature of allowing us to define our own NoiseProcess object and use all the solving interface with it. My question here is more related to the mathematical validity o…

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## [Unit testing of MTK sub-models](https://discourse.julialang.org/t/unit-testing-of-mtk-sub-models/95558)

<div class="topic-metadata">

**Author:** [@jondavis847](https://discourse.julialang.org/u/jondavis847)\
**Replies:** 3\
**Last updated:** [March 6, 2023, 11:29am UTC](https://discourse.julialang.org/t/unit-testing-of-mtk-sub-models/95558 "2023-03-06T11:29:12Z")

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Hello. I am curious about the expected behavior of MTK when composing large models from sub-models. I’m hoping to better identify and understand which sub-models I’ve designed poorly. Questions : Sometimes when I ma…

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## [Find/Implement Leapfrog method in DifferentialEquations/OrdinaryDiffEq](https://discourse.julialang.org/t/find-implement-leapfrog-method-in-differentialequations-ordinarydiffeq/95595)

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**Author:** [@TheLateKronos](https://discourse.julialang.org/u/TheLateKronos)\
**Replies:** 2\
**Last updated:** [March 6, 2023, 11:23am UTC](https://discourse.julialang.org/t/find-implement-leapfrog-method-in-differentialequations-ordinarydiffeq/95595 "2023-03-06T11:23:59Z")

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I am taking a class on computational physics. Instead of implementing everything myself, I figured I should use (and learn to use) existing frameworks. One of the class problems involves using Leapfrog integration (Wiki…

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## [Registering user-defined functions in JuMP for mixed-integer non-linear programming](https://discourse.julialang.org/t/registering-user-defined-functions-in-jump-for-mixed-integer-non-linear-programming/95522)

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**Author:** [@gmantegazza](https://discourse.julialang.org/u/gmantegazza)\
**Replies:** 4\
**Last updated:** [March 6, 2023, 5:13am UTC](https://discourse.julialang.org/t/registering-user-defined-functions-in-jump-for-mixed-integer-non-linear-programming/95522 "2023-03-06T05:13:56Z")

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Hello everyone, I have been a Julia user for some years now and I really love JuMP, however I am finding particularly difficult setting up a NLobjective in a mixed-integer program with linear constraints which correspon…

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## [Appel F1 implementation in Julia?](https://discourse.julialang.org/t/appel-f1-implementation-in-julia/95587)

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**Author:** [@LolianSh](https://discourse.julialang.org/u/LolianSh)\
**Replies:** 1\
**Last updated:** [March 6, 2023, 3:35am UTC](https://discourse.julialang.org/t/appel-f1-implementation-in-julia/95587 "2023-03-06T03:35:45Z")

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Hi, do you guys know if there is any impelemntation of the Appel hypergeometric function in Julia? AppellF1\[a, b1, b2, c, x, y\] I had a look into HypergeometricFunctions.jl, but only found the implementation of Gauss’s…

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## [Enzyme modifies my objective function after computing a gradient?](https://discourse.julialang.org/t/enzyme-modifies-my-objective-function-after-computing-a-gradient/95219)

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**Author:** [@zornsllama](https://discourse.julialang.org/u/zornsllama)\
**Replies:** 3\
**Last updated:** [March 6, 2023, 3:14am UTC](https://discourse.julialang.org/t/enzyme-modifies-my-objective-function-after-computing-a-gradient/95219 "2023-03-06T03:14:06Z")

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Hi, I’m trying to use Enzyme.jl to compute gradients for a nonlinear least squares objective function I’d like to optimize for data assimilation (to my understanding this is equivalent to what is known as weak 4DVar). T…

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## [TextFormats parser generator](https://discourse.julialang.org/t/textformats-parser-generator/95505)

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**Author:** [@tp2750](https://discourse.julialang.org/u/tp2750)\
**Replies:** 5\
**Last updated:** [March 5, 2023, 9:31am UTC](https://discourse.julialang.org/t/textformats-parser-generator/95505 "2023-03-05T09:31:47Z")

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Came across this library: GitHub - ggonnella/textformats and paper: TextFormats: Simplifying the definition and parsing of text formats in bioinformatics They define a way to describe a text-based file format (like FAST…

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## [Differential equation becomes unstable when training mixed neural ODE](https://discourse.julialang.org/t/differential-equation-becomes-unstable-when-training-mixed-neural-ode/61461)

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**Author:** [@bkuwahara](https://discourse.julialang.org/u/bkuwahara)\
**Replies:** 7\
**Last updated:** [March 5, 2023, 6:11am UTC](https://discourse.julialang.org/t/differential-equation-becomes-unstable-when-training-mixed-neural-ode/61461 "2023-03-05T06:11:46Z")

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I’m trying to use a neural network to simulate the equation for the predator population in the Lotka-Volterra model: function lotka\_volterra(du,u,p,t) x, y = u α, β = (1.5,1.0) du\[1\] = dx = α\*x - β\*x\*y du\[2\] = N…

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## [\[Zygote\] Derivative of derivative compilation time](https://discourse.julialang.org/t/zygote-derivative-of-derivative-compilation-time/95537)

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**Author:** [@mariusd](https://discourse.julialang.org/u/mariusd)\
**Replies:** 4\
**Last updated:** [March 4, 2023, 9:57pm UTC](https://discourse.julialang.org/t/zygote-derivative-of-derivative-compilation-time/95537 "2023-03-04T21:57:53Z")

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In the following code I calculate derivative fx, then derivative of derivative fxy, and then fxyz. The code works and gives the correct result, however the compilation time is huge for the fxyz derivative. Is there a wa…

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## [Calculating displacement vectors between Agents](https://discourse.julialang.org/t/calculating-displacement-vectors-between-agents/95458)

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**Author:** [@Niall](https://discourse.julialang.org/u/Niall)\
**Replies:** 3\
**Last updated:** [March 4, 2023, 7:07pm UTC](https://discourse.julialang.org/t/calculating-displacement-vectors-between-agents/95458 "2023-03-04T19:07:15Z")

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Hi. I’m having problems (re-)implementing the Flocking model in Agents. Whenever I run it, flocks tend to bounce off the supposedly periodic boundaries, and when I analyse this more closely, the individual agents ‘stick’…

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## [CUDA atomic add for ForwardDiff duals?](https://discourse.julialang.org/t/cuda-atomic-add-for-forwarddiff-duals/85968)

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**Author:** [@Mark\_Lau](https://discourse.julialang.org/u/Mark_Lau)\
**Replies:** 2\
**Last updated:** [August 19, 2022, 5:59pm UTC](https://discourse.julialang.org/t/cuda-atomic-add-for-forwarddiff-duals/85968 "2022-08-19T17:59:41Z")

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Hi everyone, I’ve been trying to auto differentiate some code that runs on the GPU using ForwardDiff. Some of the kernels perform an atomic addition operation via CUDA.@atomic, but that doesn’t seem to be supported for F…

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## [Spline fit from DataInterpolations erroring out with ModelingToolkit symbolic derivative](https://discourse.julialang.org/t/spline-fit-from-datainterpolations-erroring-out-with-modelingtoolkit-symbolic-derivative/95417)

<div class="topic-metadata">

**Author:** [@aditya-sengupta](https://discourse.julialang.org/u/aditya-sengupta)\
**Replies:** 4\
**Last updated:** [March 4, 2023, 6:40pm UTC](https://discourse.julialang.org/t/spline-fit-from-datainterpolations-erroring-out-with-modelingtoolkit-symbolic-derivative/95417 "2023-03-04T18:40:38Z")

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I’m trying to take a ModelingToolkit symbolic derivative of a variable whose values I’m getting with a DataInterpolations spline, and it’s unable to evaluate the derivative of a constant so I can’t solve the system. MWE: …

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## [Structural\_simplify unexpected ERROR when applied twice in a row](https://discourse.julialang.org/t/structural-simplify-unexpected-error-when-applied-twice-in-a-row/95540)

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**Author:** [@halejulia](https://discourse.julialang.org/u/halejulia)\
**Replies:** 2\
**Last updated:** [March 4, 2023, 2:47pm UTC](https://discourse.julialang.org/t/structural-simplify-unexpected-error-when-applied-twice-in-a-row/95540 "2023-03-04T14:47:18Z")

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I mentioned this on slack, but I took me a while to create an MWE, so I’m posting it here again. Here is the MWE: using ModelingToolkit @variables t u(t)\[1:2\] D=Differential(t) eqs = \[u\[1\] ~ 1 D…

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## [\[ReverseDiff.jl\] How to do nested differentiation?](https://discourse.julialang.org/t/reversediff-jl-how-to-do-nested-differentiation/95542)

<div class="topic-metadata">

**Author:** [@mariusd](https://discourse.julialang.org/u/mariusd)\
**Replies:** 0\
**Last updated:** [March 4, 2023, 2:00pm UTC](https://discourse.julialang.org/t/reversediff-jl-how-to-do-nested-differentiation/95542 "2023-03-04T14:00:12Z")

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See the following example. I do calculate the derivative of f w.r.t. to x, called fx. Then I calculate the derivative of fx w.r.t. to y, called fxy. The function fxyz is computed similarly. The output of fx is correct, …

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## [StochasticDiffEq Tau-Leaping maxiters](https://discourse.julialang.org/t/stochasticdiffeq-tau-leaping-maxiters/95517)

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**Author:** [@arnold-c](https://discourse.julialang.org/u/arnold-c)\
**Replies:** 10\
**Last updated:** [March 4, 2023, 5:49am UTC](https://discourse.julialang.org/t/stochasticdiffeq-tau-leaping-maxiters/95517 "2023-03-04T05:49:13Z")

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I’m relatively new to Julia and JumpProcesses.jl, so apologies if this is somewhat basic, but I’m having an issue trying to convert the example SIR model with tau-leaping from density-dependent to frequency dependent i.e…

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## [Is it worthwhile for a regular Julia user to learn SQL?](https://discourse.julialang.org/t/is-it-worthwhile-for-a-regular-julia-user-to-learn-sql/95387)

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**Author:** [@oviedorodolfo](https://discourse.julialang.org/u/oviedorodolfo)\
**Replies:** 4\
**Last updated:** [March 4, 2023, 2:03am UTC](https://discourse.julialang.org/t/is-it-worthwhile-for-a-regular-julia-user-to-learn-sql/95387 "2023-03-04T02:03:56Z")

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Is it worthwhile to learn SQL for someone who will seldom need to access SQL databases? I so, what dialect?

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## [Continuously plot to the same window on the fly](https://discourse.julialang.org/t/continuously-plot-to-the-same-window-on-the-fly/95498)

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**Author:** [@linwaytin](https://discourse.julialang.org/u/linwaytin)\
**Replies:** 2\
**Last updated:** [March 3, 2023, 9:08pm UTC](https://discourse.julialang.org/t/continuously-plot-to-the-same-window-on-the-fly/95498 "2023-03-03T21:08:08Z")

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I have for loop which runs some computation. For debugging, I want to see the output “real-time”. One possible way to do that is continuously plotting add points to the same graph. using Gaston plot(something) for iter=…

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## [Issue with lazy constraints on Xpress](https://discourse.julialang.org/t/issue-with-lazy-constraints-on-xpress/95463)

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**Author:** [@Diego](https://discourse.julialang.org/u/Diego)\
**Replies:** 4\
**Last updated:** [March 3, 2023, 8:56pm UTC](https://discourse.julialang.org/t/issue-with-lazy-constraints-on-xpress/95463 "2023-03-03T20:56:05Z")

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Dear community, I am giving a try to Lazy Constraints and can make a very simple case run with Xpress, however, there is not an issue at all with GLPK. Can you please have a look and let us know where the problem is? T…

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## [Sum or convolution of discrete uniform random variable](https://discourse.julialang.org/t/sum-or-convolution-of-discrete-uniform-random-variable/15426)

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**Author:** [@leclere](https://discourse.julialang.org/u/leclere)\
**Replies:** 10\
**Last updated:** [March 3, 2023, 2:22pm UTC](https://discourse.julialang.org/t/sum-or-convolution-of-discrete-uniform-random-variable/15426 "2023-03-03T14:22:14Z")

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Hello, I am interested in the convolution of random independent discrete variables (and in particular uniform discrete random variables). Is there an efficient way of constructing this ? Or should I just write my own co…

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## [Animation of a GraphPlots in an Array](https://discourse.julialang.org/t/animation-of-a-graphplots-in-an-array/94793)

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**Author:** [@flobe](https://discourse.julialang.org/u/flobe)\
**Replies:** 2\
**Last updated:** [March 3, 2023, 1:37pm UTC](https://discourse.julialang.org/t/animation-of-a-graphplots-in-an-array/94793 "2023-03-03T13:37:34Z")

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Hi all, I have a big simulation loop resulting in a graphplot for each timestep. I store each of those plots in an array. Ultimately, I’d like to animate over all entries in this array. The minimal working example looks…

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## [How to create a series of interactive plots using GLMakie?](https://discourse.julialang.org/t/how-to-create-a-series-of-interactive-plots-using-glmakie/95412)

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**Author:** [@albrightand](https://discourse.julialang.org/u/albrightand)\
**Replies:** 1\
**Last updated:** [March 2, 2023, 4:49pm UTC](https://discourse.julialang.org/t/how-to-create-a-series-of-interactive-plots-using-glmakie/95412 "2023-03-02T16:49:10Z")

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I need to make an interactive plot that takes mouse clicks on an image plot as input. There will be a series of plots with an image on top and a ‘Done’ button at the bottom. The program should plot each image in its own …

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## [Julia seems to be running multithreaded when I don't want it to](https://discourse.julialang.org/t/julia-seems-to-be-running-multithreaded-when-i-dont-want-it-to/95391)

<div class="topic-metadata">

**Author:** [@nvenkov1](https://discourse.julialang.org/u/nvenkov1)\
**Replies:** 67\
**Last updated:** [March 2, 2023, 12:20pm UTC](https://discourse.julialang.org/t/julia-seems-to-be-running-multithreaded-when-i-dont-want-it-to/95391 "2023-03-02T12:20:08Z")

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I coded an algorithm called CGS2, i.e., re-orthogonalized classical Gram-Schmidt, which I need to benchmark. I absolutely need my test to run on a single thread. To make sure it is the case, I write the following at the …

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## [\[Turing.jl\] How to generate samples ("observations") from a model](https://discourse.julialang.org/t/turing-jl-how-to-generate-samples-observations-from-a-model/95258)

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**Author:** [@dmetivie](https://discourse.julialang.org/u/dmetivie)\
**Replies:** 6\
**Last updated:** [March 2, 2023, 8:05am UTC](https://discourse.julialang.org/t/turing-jl-how-to-generate-samples-observations-from-a-model/95258 "2023-03-02T08:05:20Z")

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Hello, Let say I define a Turing model and would like to use it to generate not only from prior but also some associated y observations. Here is an example: @model function mymodel(y::AbstractVector{F}) where {F\<:Real}…

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## [Example for solving a QP (or LP) in Gurobi directly (without JuMP)](https://discourse.julialang.org/t/example-for-solving-a-qp-or-lp-in-gurobi-directly-without-jump/94108)

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**Author:** [@jacob-roth](https://discourse.julialang.org/u/jacob-roth)\
**Replies:** 12\
**Last updated:** [March 2, 2023, 1:21am UTC](https://discourse.julialang.org/t/example-for-solving-a-qp-or-lp-in-gurobi-directly-without-jump/94108 "2023-03-02T01:21:55Z")

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Similar to this question, I am wondering if anyone has example Julia code that they would be willing to share for how to pass vectors and matrices directly into Gurobi.jl to construct/solve a model. The Gurobi C interfac…

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## [Broken range](https://discourse.julialang.org/t/broken-range/95347)

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**Author:** [@Sergey\_Novak](https://discourse.julialang.org/u/Sergey_Novak)\
**Replies:** 17\
**Last updated:** [March 1, 2023, 9:21pm UTC](https://discourse.julialang.org/t/broken-range/95347 "2023-03-01T21:21:19Z")

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Hello, i try plot next graphic for range The problem is that the picture looks too discrete. I built it with a modified range and it looked smoother. Why is that? I0range = range( -1.509460, -1.509490, length = 5000 ) …

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## [JuMP: Control automatic differentiation of user defined function](https://discourse.julialang.org/t/jump-control-automatic-differentiation-of-user-defined-function/95380)

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**Author:** [@mgreifenstein](https://discourse.julialang.org/u/mgreifenstein)\
**Replies:** 4\
**Last updated:** [March 1, 2023, 8:33pm UTC](https://discourse.julialang.org/t/jump-control-automatic-differentiation-of-user-defined-function/95380 "2023-03-01T20:33:54Z")

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Hi all, I am currently working on a code that is supposed to fit a model to experimental coherent Anti-Stokes Raman spectra which has about 9 decision variables, depending on the case. Because the computations in this m…

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## [JuMP/Gurobi: optimize! returns INFEASIBLE, but there is feasible point](https://discourse.julialang.org/t/jump-gurobi-optimize-returns-infeasible-but-there-is-feasible-point/95019)

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**Author:** [@Ethan-Russell](https://discourse.julialang.org/u/Ethan-Russell)\
**Replies:** 12\
**Last updated:** [March 1, 2023, 2:30pm UTC](https://discourse.julialang.org/t/jump-gurobi-optimize-returns-infeasible-but-there-is-feasible-point/95019 "2023-03-01T14:30:13Z")

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I am solving a very large (\>1M variables) linear program with Gurobi. After 3 hours, Gurobi returns with status INFEASIBLE. However, if I run primal\_feasibility\_report with all variables being zero, it returns an empty…

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## [Issues with broadcasting min and max operators to matrixes in JuMP expression](https://discourse.julialang.org/t/issues-with-broadcasting-min-and-max-operators-to-matrixes-in-jump-expression/95385)

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**Author:** [@templenash](https://discourse.julialang.org/u/templenash)\
**Replies:** 1\
**Last updated:** [March 1, 2023, 1:20pm UTC](https://discourse.julialang.org/t/issues-with-broadcasting-min-and-max-operators-to-matrixes-in-jump-expression/95385 "2023-03-01T13:20:13Z")

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Hello, New to JuMP and trying to implement a matrix-based expression in JuMP that uses min and max operators broadcasted to the vector. Having trouble getting the min and max operators working in the ‘tx’ expression, wa…

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## [Can I specify color of each rectangle in Makie.jl's heatmap?](https://discourse.julialang.org/t/can-i-specify-color-of-each-rectangle-in-makie-jls-heatmap/95314)

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**Author:** [@Tomas\_Pevny](https://discourse.julialang.org/u/Tomas_Pevny)\
**Replies:** 4\
**Last updated:** [March 1, 2023, 10:33am UTC](https://discourse.julialang.org/t/can-i-specify-color-of-each-rectangle-in-makie-jls-heatmap/95314 "2023-03-01T10:33:22Z")

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Hi all, I would like to plot a 2d map in Makie, where I can specify exactly a color in each rectangle. Something like a heatmap, where the color would be prescribed and not taken from a colormap. I have tried to fudge t…

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## [Is there a library function to fit an identity-link NB1 regression model?](https://discourse.julialang.org/t/is-there-a-library-function-to-fit-an-identity-link-nb1-regression-model/92824)

<div class="topic-metadata">

**Author:** [@jacques1](https://discourse.julialang.org/u/jacques1)\
**Replies:** 8\
**Last updated:** [March 1, 2023, 8:37am UTC](https://discourse.julialang.org/t/is-there-a-library-function-to-fit-an-identity-link-nb1-regression-model/92824 "2023-03-01T08:37:14Z")

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I would like to build an identity link negative binomial 1 glm model for some data (where negative binomial 1 means that the dispersion parameter is of the form (1 + theta)\*mean). This means I need to simultaneously cont…

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