# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=369

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**Page:** 370

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## [Plotting an ellipsoid as 2D surface in 3D, given the principal axes](https://discourse.julialang.org/t/plotting-an-ellipsoid-as-2d-surface-in-3d-given-the-principal-axes/60393)

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**Author:** [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Replies:** 14\
**Last updated:** [May 2, 2021, 3:28pm UTC](https://discourse.julialang.org/t/plotting-an-ellipsoid-as-2d-surface-in-3d-given-the-principal-axes/60393 "2021-05-02T15:28:17Z")

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Hi there, Let’s say I have some lengths \[5.0, 2.0, 1.0\] and I want to plot an ellipsoid whose axis have these lengths as a surface in 3D. Extra bonus if I can also provide two angles of rotation for azimuth / polar angl…

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## [Better way to solve jacobian dependent differential equation](https://discourse.julialang.org/t/better-way-to-solve-jacobian-dependent-differential-equation/60259)

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**Author:** [@willian](https://discourse.julialang.org/u/willian)\
**Replies:** 4\
**Last updated:** [May 2, 2021, 3:18pm UTC](https://discourse.julialang.org/t/better-way-to-solve-jacobian-dependent-differential-equation/60259 "2021-05-02T15:18:47Z")

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What is the best way to solve the following differential equations ? I mean, I could solve the first equation x(t) alone and use the solutions to run the solver again and find P(t). I would like to know if there is a…

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## [How to do multiple imputation on Julia?](https://discourse.julialang.org/t/how-to-do-multiple-imputation-on-julia/17713)

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**Author:** [@Juan](https://discourse.julialang.org/u/Juan)\
**Replies:** 15\
**Last updated:** [May 2, 2021, 7:46am UTC](https://discourse.julialang.org/t/how-to-do-multiple-imputation-on-julia/17713 "2021-05-02T07:46:02Z")

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I’ve found the package Impute.jl but it seems it’s only able to use these simple methods: drop - remove missing locf - last observation carried forward nocb - next observation carried backward interp - linear interpola…

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## [Status of integration, optimization, and nl solvers](https://discourse.julialang.org/t/status-of-integration-optimization-and-nl-solvers/60025)

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**Author:** [@amrods](https://discourse.julialang.org/u/amrods)\
**Replies:** 22\
**Last updated:** [May 2, 2021, 3:27am UTC](https://discourse.julialang.org/t/status-of-integration-optimization-and-nl-solvers/60025 "2021-05-02T03:27:22Z")

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I’m working on a project in which, given a vector of parameters θ, I have to solve a nonlinear system of equations that involve some integrals. After solving the system, I need to optimize with respect to θ to obtain opt…

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## [Help with Gaussian Mixer Model in Turing.jl](https://discourse.julialang.org/t/help-with-gaussian-mixer-model-in-turing-jl/60396)

<div class="topic-metadata">

**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 0\
**Last updated:** [May 1, 2021, 8:10pm UTC](https://discourse.julialang.org/t/help-with-gaussian-mixer-model-in-turing-jl/60396 "2021-05-01T20:10:28Z")

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Random.seed!(3) N = 30 μs = \[-3.5, 0.0\] x = mapreduce(c -\> rand(MvNormal(\[μs\[c\], μs\[c\]\], 1.), N), hcat, 1:2) using Turing, MCMCChains model GaussianMixtureModel(x) = begin D, N = size(x) # Draw the pa…

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## [In BAT.jl I'm unable to find the Log Denstiy Value](https://discourse.julialang.org/t/in-bat-jl-im-unable-to-find-the-log-denstiy-value/60390)

<div class="topic-metadata">

**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 0\
**Last updated:** [May 1, 2021, 5:53pm UTC](https://discourse.julialang.org/t/in-bat-jl-im-unable-to-find-the-log-denstiy-value/60390 "2021-05-01T17:53:27Z")

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data = vcat( rand(Normal(-1.0, 0.5), 500), rand(Normal( 2.0, 0.5), 1000) ) hist = append!(Histogram(-2:0.1:4), data) function fit\_function(p::NamedTuple{(:a, :mu, :sigma)}, x::Real) p.a\[1\] \* pdf(Normal(p.mu\[…

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## [Which optimization package should I use?](https://discourse.julialang.org/t/which-optimization-package-should-i-use/60230)

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**Author:** [@Piotr](https://discourse.julialang.org/u/Piotr)\
**Replies:** 13\
**Last updated:** [May 1, 2021, 3:05pm UTC](https://discourse.julialang.org/t/which-optimization-package-should-i-use/60230 "2021-05-01T15:05:25Z")

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Hello everyone, I have an optimization (minimization) problem\* in Julia to solve and I’m a looking for a package with which, most importantly, I can do it fast. Specifically: the problem is in two variables (but it m…

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## [Nonlinear PDE with neural network](https://discourse.julialang.org/t/nonlinear-pde-with-neural-network/60358)

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**Author:** [@narayan](https://discourse.julialang.org/u/narayan)\
**Replies:** 1\
**Last updated:** [May 1, 2021, 11:10am UTC](https://discourse.julialang.org/t/nonlinear-pde-with-neural-network/60358 "2021-05-01T11:10:09Z")

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can we solve nonlinear PDE with the package NeuralPDE.jl? If yes, then how?

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## [How well Apache Arrow’s zero copy methodology is supported?](https://discourse.julialang.org/t/how-well-apache-arrow-s-zero-copy-methodology-is-supported/59797)

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**Author:** [@Sami](https://discourse.julialang.org/u/Sami)\
**Replies:** 24\
**Last updated:** [May 1, 2021, 5:08am UTC](https://discourse.julialang.org/t/how-well-apache-arrow-s-zero-copy-methodology-is-supported/59797 "2021-05-01T05:08:50Z")

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I made a large Arrow file that doesn’t fit into the RAM of my PC. The file is about 13 GB and 170 million rows. I wanted to test how well I can analyze “big data” with Julia’s Arrow.jl package. After reading the file (a…

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## [Julian design for API library with Websocket client](https://discourse.julialang.org/t/julian-design-for-api-library-with-websocket-client/60281)

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**Author:** [@Spirarel](https://discourse.julialang.org/u/Spirarel)\
**Replies:** 2\
**Last updated:** [May 1, 2021, 12:00am UTC](https://discourse.julialang.org/t/julian-design-for-api-library-with-websocket-client/60281 "2021-05-01T00:00:15Z")

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I’m writing a Julia library to interact with an API that communicates via HTTP.Websockets. I’m struggling to find good, non-toy-repl, examples that illustrate the kind of contract a Julia dev would expect. In OO land it’…

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## [Plotly hovermode](https://discourse.julialang.org/t/plotly-hovermode/60336)

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**Author:** [@cyrieln](https://discourse.julialang.org/u/cyrieln)\
**Replies:** 1\
**Last updated:** [April 30, 2021, 6:25pm UTC](https://discourse.julialang.org/t/plotly-hovermode/60336 "2021-04-30T18:25:36Z")

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Hi there! I was wondering if it is possible to change Plots’ plotlyjs default hovermode to closest. I have a scatterplot with thousands of points and I’d like to show hover info on each point but only the closest one. R…

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## [Matrix of downstream nodes using LightGraphs](https://discourse.julialang.org/t/matrix-of-downstream-nodes-using-lightgraphs/60314)

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**Author:** [@Cappuccio](https://discourse.julialang.org/u/Cappuccio)\
**Replies:** 0\
**Last updated:** [April 30, 2021, 1:55pm UTC](https://discourse.julialang.org/t/matrix-of-downstream-nodes-using-lightgraphs/60314 "2021-04-30T13:55:14Z")

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Does anyone have an idea as to how you would create a vector of ‘downstream nodes’ for a given node in a network, using LightGraphs? For example, see the network attached, all downstream nodes of 17 would be \[19, 20, …

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## [CuArrays using @views+mul!+transpose+slicing](https://discourse.julialang.org/t/cuarrays-using-views-mul-transpose-slicing/60289)

<div class="topic-metadata">

**Author:** [@albheim](https://discourse.julialang.org/u/albheim)\
**Replies:** 4\
**Last updated:** [April 30, 2021, 11:13am UTC](https://discourse.julialang.org/t/cuarrays-using-views-mul-transpose-slicing/60289 "2021-04-30T11:13:31Z")

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Hi, had a problem when using CuArrays for a specific operation. It is optimized for CPU and it would be nice if it worked with the same code on GPU so there was no need to dispatch specifically on it. a = cu(randn(10, 1…

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## [How to pass constraints in NLsolve?](https://discourse.julialang.org/t/how-to-pass-constraints-in-nlsolve/60219)

<div class="topic-metadata">

**Author:** [@amrods](https://discourse.julialang.org/u/amrods)\
**Replies:** 5\
**Last updated:** [April 30, 2021, 10:49am UTC](https://discourse.julialang.org/t/how-to-pass-constraints-in-nlsolve/60219 "2021-04-30T10:49:50Z")

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I am solving 2-variable system of first order conditions for an optimization problem with NLsolve. I know that the optimal values of the optimization problem satisfy some conditions. For example, the optimal values shoul…

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## [Unable to plot a sphere surface using Plots package](https://discourse.julialang.org/t/unable-to-plot-a-sphere-surface-using-plots-package/60194)

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**Author:** [@AAlshammaa](https://discourse.julialang.org/u/AAlshammaa)\
**Replies:** 7\
**Last updated:** [April 29, 2021, 8:54pm UTC](https://discourse.julialang.org/t/unable-to-plot-a-sphere-surface-using-plots-package/60194 "2021-04-29T20:54:23Z")

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I am trying to follow a tutorial on youtube for SVD, and the instructor created a sphere using Python. I am trying to translate the code to Julia n = 100 u = range(-π, π; length = n) v = range(0, π; length = n) x = cos.…

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## [Way to Avoid Checking Parameters Fall in Bounds for Distributions.jl](https://discourse.julialang.org/t/way-to-avoid-checking-parameters-fall-in-bounds-for-distributions-jl/59436)

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**Author:** [@ParadaCarleton](https://discourse.julialang.org/u/ParadaCarleton)\
**Replies:** 8\
**Last updated:** [April 30, 2021, 1:35am UTC](https://discourse.julialang.org/t/way-to-avoid-checking-parameters-fall-in-bounds-for-distributions-jl/59436 "2021-04-30T01:35:32Z")

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Is there a way to avoid checking whether parameters for a distribution fall within the required bounds (e.g. positives only for beta-binomial)? It should make sampling with Turing.jl faster, and can also be helpful when …

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## [How to tackle a Stefan problem in ModelingToolkit](https://discourse.julialang.org/t/how-to-tackle-a-stefan-problem-in-modelingtoolkit/59846)

<div class="topic-metadata">

**Author:** [@feanor12](https://discourse.julialang.org/u/feanor12)\
**Replies:** 3\
**Last updated:** [April 29, 2021, 3:13pm UTC](https://discourse.julialang.org/t/how-to-tackle-a-stefan-problem-in-modelingtoolkit/59846 "2021-04-29T15:13:39Z")

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I have a problem similar to a Stefan problem and I wanted to ask if there is any tooling to make this kind of problem simpler/more efficient to solve. Especially the moving boundary seems difficult to achieve.

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## [EnsembleThreads slower than EnsembleSerial or EnsembleDistributed](https://discourse.julialang.org/t/ensemblethreads-slower-than-ensembleserial-or-ensembledistributed/59511)

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**Author:** [@ograsdijk](https://discourse.julialang.org/u/ograsdijk)\
**Replies:** 3\
**Last updated:** [April 29, 2021, 3:09pm UTC](https://discourse.julialang.org/t/ensemblethreads-slower-than-ensembleserial-or-ensembledistributed/59511 "2021-04-29T15:09:43Z")

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For my ode system EnsembleThreads (6 threads) is slower than either EnsembleSerial or EnsembleDistributed (6 processes). My specs are Windows 10 and a 6 core i8700k with 32Gb ram and running Julia V1.6. I’m running opti…

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## [Error in simple Turing model with ReverseDiff](https://discourse.julialang.org/t/error-in-simple-turing-model-with-reversediff/60128)

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**Author:** [@opera\_malenky](https://discourse.julialang.org/u/opera_malenky)\
**Replies:** 6\
**Last updated:** [April 29, 2021, 2:56pm UTC](https://discourse.julialang.org/t/error-in-simple-turing-model-with-reversediff/60128 "2021-04-29T14:56:40Z")

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I had a model that was running until about two weeks ago, but suddenly stopped. I thought I’d post here before filing an issue - it’s not clear to me if this is more of a reversediff issue or a Turing issue or something …

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## [Adaptive step-size algorithm for stiff SDE solvers in StochasticDiffEq.jl](https://discourse.julialang.org/t/adaptive-step-size-algorithm-for-stiff-sde-solvers-in-stochasticdiffeq-jl/59785)

<div class="topic-metadata">

**Author:** [@alvestad10](https://discourse.julialang.org/u/alvestad10)\
**Replies:** 2\
**Last updated:** [April 29, 2021, 1:57pm UTC](https://discourse.julialang.org/t/adaptive-step-size-algorithm-for-stiff-sde-solvers-in-stochasticdiffeq-jl/59785 "2021-04-29T13:57:56Z")

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Could someone point me in the direction of where to find info on how the time-stepping method for stiff SDE solvers is implemented? I am mainly interested in how the ImplicitEM solver does the adaptive stepsize control, …

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## [Normalized nrow in a GroupedDataFrame](https://discourse.julialang.org/t/normalized-nrow-in-a-groupeddataframe/60226)

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**Author:** [@Storopoli](https://discourse.julialang.org/u/Storopoli)\
**Replies:** 4\
**Last updated:** [April 29, 2021, 12:22pm UTC](https://discourse.julialang.org/t/normalized-nrow-in-a-groupeddataframe/60226 "2021-04-29T12:22:59Z")

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What is the best way to do a “normalized” nrow in a gdf? using DataFrames using Chain df = DataFrame(id=1:6, name=\["Aaron Aardvark", "Belen Barboza", "春 陈", "Даниил Ду…

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## [DiffEq: SavingCallback, save befor and after other callback](https://discourse.julialang.org/t/diffeq-savingcallback-save-befor-and-after-other-callback/59263)

<div class="topic-metadata">

**Author:** [@hexaeder](https://discourse.julialang.org/u/hexaeder)\
**Replies:** 7\
**Last updated:** [April 29, 2021, 11:21am UTC](https://discourse.julialang.org/t/diffeq-savingcallback-save-befor-and-after-other-callback/59263 "2021-04-29T11:21:03Z")

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I use a callback to alter the parameters p of my system. I also use a SavingCallback to save some function f(u,p) at every timestep. The parameter changing callback has the option save\_positions=(true,true) and saves th…

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## [How to plot with manually created legend entries?](https://discourse.julialang.org/t/how-to-plot-with-manually-created-legend-entries/60024)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 14\
**Last updated:** [April 29, 2021, 10:52am UTC](https://discourse.julialang.org/t/how-to-plot-with-manually-created-legend-entries/60024 "2021-04-29T10:52:04Z")

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I created my own legend entries following the docs, now I’d like to plot with them. MWE: using GLMakie legendentries = Dict("A" =\> LineElement(linestyle = nothing, linewidth = 0.3, color = :red), "…

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## [No method matching promote\_shape](https://discourse.julialang.org/t/no-method-matching-promote-shape/60021)

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**Author:** [@zlq178](https://discourse.julialang.org/u/zlq178)\
**Replies:** 7\
**Last updated:** [April 29, 2021, 6:07am UTC](https://discourse.julialang.org/t/no-method-matching-promote-shape/60021 "2021-04-29T06:07:48Z")

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Here is a small example. using JuMP,Mosek,MosekTools u=rand(3,1) M\_SDP = Model(Mosek.Optimizer) #set\_silent(model) #set\_optimizer\_attribute(M\_SDP, "MSK\_IPAR\_LOG", 0) @variable(M\_SDP,buro\[1:3,1\]) # Z \>= 0, PSD @variable…

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## [Access infeasible optimization results ( GLPK with semicontinuous variable )](https://discourse.julialang.org/t/access-infeasible-optimization-results-glpk-with-semicontinuous-variable/59972)

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**Author:** [@Runhong\_Huang](https://discourse.julialang.org/u/Runhong_Huang)\
**Replies:** 6\
**Last updated:** [April 28, 2021, 9:29pm UTC](https://discourse.julialang.org/t/access-infeasible-optimization-results-glpk-with-semicontinuous-variable/59972 "2021-04-28T21:29:03Z")

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Hi all, I have a question regarding accessing infeasible optimization results. For example, the following optimization does not have a feasible solution. However, despite the infeasibility, it is still able to give the…

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## [Ipopt Set Attribute](https://discourse.julialang.org/t/ipopt-set-attribute/59982)

<div class="topic-metadata">

**Author:** [@user1200](https://discourse.julialang.org/u/user1200)\
**Replies:** 4\
**Last updated:** [April 28, 2021, 9:28pm UTC](https://discourse.julialang.org/t/ipopt-set-attribute/59982 "2021-04-28T21:28:14Z")

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Hello I got little issue with model = Model(with\_optimizer(Ipopt.Optimizer, tol=1e-9)) #or set\_optimizer\_attribute(model, “constr\_viol\_tol”, 0) #throws this error when called optimize! It is a valid option, but …

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## [Dual{::ForwardDiff...} type error when JuMP tries autodiff User-defined Function](https://discourse.julialang.org/t/dual-forwarddiff-type-error-when-jump-tries-autodiff-user-defined-function/25639)

<div class="topic-metadata">

**Author:** [@KestutisMa](https://discourse.julialang.org/u/KestutisMa)\
**Replies:** 20\
**Last updated:** [April 28, 2021, 9:26pm UTC](https://discourse.julialang.org/t/dual-forwarddiff-type-error-when-jump-tries-autodiff-user-defined-function/25639 "2021-04-28T21:26:08Z")

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Hi, I am trying to optimize User-defined function with and I got this error: ERROR: LoadError: MethodError: no method matching Float64(::ForwardDiff.Dual{ForwardDiff.Tag{getfield(JuMP, Symbol("##84#86")){typeof(min\_f)},…

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## [Solvers using JuMP and Clp](https://discourse.julialang.org/t/solvers-using-jump-and-clp/60193)

<div class="topic-metadata">

**Author:** [@marouane](https://discourse.julialang.org/u/marouane)\
**Replies:** 0\
**Last updated:** [April 28, 2021, 6:44pm UTC](https://discourse.julialang.org/t/solvers-using-jump-and-clp/60193 "2021-04-28T18:44:51Z")

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I have this function, that is written using JuMP@0.18 and Clp and im struggling how can i update the syntax when using JuMP@0.21\` specially when it comes to the solver part: function scan(c::Channel) i = 1 …

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## [ModelingToolkit.jl ODESystems with a forcing function: how to autodiff?](https://discourse.julialang.org/t/modelingtoolkit-jl-odesystems-with-a-forcing-function-how-to-autodiff/58823)

<div class="topic-metadata">

**Author:** [@Dhruva2](https://discourse.julialang.org/u/Dhruva2)\
**Replies:** 2\
**Last updated:** [April 28, 2021, 3:54pm UTC](https://discourse.julialang.org/t/modelingtoolkit-jl-odesystems-with-a-forcing-function-how-to-autodiff/58823 "2021-04-28T15:54:08Z")

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Hi! Lots of differential equations models incorporate an external input function (e.g. a control system doing reference tracking). When I build models of this form in ModelingToolkit.jl, they don’t seem to be differenti…

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## [ForwardDiff and Floats](https://discourse.julialang.org/t/forwarddiff-and-floats/47596)

<div class="topic-metadata">

**Author:** [@danicaratelli](https://discourse.julialang.org/u/danicaratelli)\
**Replies:** 13\
**Last updated:** [April 28, 2021, 2:18pm UTC](https://discourse.julialang.org/t/forwarddiff-and-floats/47596 "2021-04-28T14:18:58Z")

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Hello, I am trying to use Ipopt in JuMP to solve a minimization problem with automatic differentiation. I am aware that I need to specify the types of the inputs as Real rather than Float64 but it’s not clear to me to …

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