# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=515

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**Page:** 516

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## [Differential equation solver example gives an error: MethodError: no method matching OrdinaryDiffEq.DEOptions](https://discourse.julialang.org/t/differential-equation-solver-example-gives-an-error-methoderror-no-method-matching-ordinarydiffeq-deoptions/18001)

<div class="topic-metadata">

**Author:** [@PeterXG](https://discourse.julialang.org/u/PeterXG)\
**Replies:** 6\
**Last updated:** [December 3, 2018, 12:32pm UTC](https://discourse.julialang.org/t/differential-equation-solver-example-gives-an-error-methoderror-no-method-matching-ordinarydiffeq-deoptions/18001 "2018-12-03T12:32:48Z")

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Dear All, I run the sample code to solve a differential equation from tutorial. const p0 = 0.2; const q0 = 0.3; const v0 = 1; const d0 = 5 const p1 = 0.2; const q1 = 0.3; const v1 = 1; const d1 = 1 const d2 = 1; const …

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## [Difficulties with DifferentialEquations package](https://discourse.julialang.org/t/difficulties-with-differentialequations-package/18204)

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**Author:** [@BLI](https://discourse.julialang.org/u/BLI)\
**Replies:** 13\
**Last updated:** [December 2, 2018, 9:14pm UTC](https://discourse.julialang.org/t/difficulties-with-differentialequations-package/18204 "2018-12-02T21:14:33Z")

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I’m testing the DifferentialEquations package on a model I developed ca. 1993 (just dug it of the archives…). I try to simulate 5 Argon molecules bouncing around in 2D, locked up between “Lennard-Jones” like potential wa…

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## [Difficulty to understand the JuMP problem setting](https://discourse.julialang.org/t/difficulty-to-understand-the-jump-problem-setting/18112)

<div class="topic-metadata">

**Author:** [@Tero\_Frondelius](https://discourse.julialang.org/u/Tero_Frondelius)\
**Replies:** 13\
**Last updated:** [December 2, 2018, 5:50pm UTC](https://discourse.julialang.org/t/difficulty-to-understand-the-jump-problem-setting/18112 "2018-12-02T17:50:51Z")

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Here is my MWE of the problem: using JuMP using Clp Random.seed!(2017) xlocs, ylocs = rand(5), rand(5) function demo\_problem(x,y) counter = 0 for (xx,yy) in zip(x,y) val = xx - yy if (…

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## [How to render multiple windows in Makie.jl?](https://discourse.julialang.org/t/how-to-render-multiple-windows-in-makie-jl/18221)

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**Author:** [@NanFangHong](https://discourse.julialang.org/u/NanFangHong)\
**Replies:** 0\
**Last updated:** [December 2, 2018, 3:29pm UTC](https://discourse.julialang.org/t/how-to-render-multiple-windows-in-makie-jl/18221 "2018-12-02T15:29:06Z")

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Hi, may I have your help? How to render multiple windows in Makie.jl?

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## [User defined objective function to run MICP](https://discourse.julialang.org/t/user-defined-objective-function-to-run-micp/16992)

<div class="topic-metadata">

**Author:** [@coiacy](https://discourse.julialang.org/u/coiacy)\
**Replies:** 18\
**Last updated:** [December 2, 2018, 11:01am UTC](https://discourse.julialang.org/t/user-defined-objective-function-to-run-micp/16992 "2018-12-02T11:01:21Z")

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I have the following objective function (w is the variable vector of size nx): function obj\_trace(w::Array{Float64,1}) dg = Diagonal(w) M = F' \* (gamma \\ dg) \* F + eye(nx) obj = trace(inv(M)) return obj …

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## [What fileformat to use to load data for high performance computing](https://discourse.julialang.org/t/what-fileformat-to-use-to-load-data-for-high-performance-computing/4786)

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**Author:** [@Tomas\_Pevny](https://discourse.julialang.org/u/Tomas_Pevny)\
**Replies:** 37\
**Last updated:** [December 1, 2018, 3:41pm UTC](https://discourse.julialang.org/t/what-fileformat-to-use-to-load-data-for-high-performance-computing/4786 "2018-12-01T15:41:02Z")

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Hi All, I am working on a project, where I want to do some machine learning over large data (about 50Gb) stored in AWS S3. I would like to ask people about their opinions and experiences with the dataformat they use and…

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## [How to create tracked \`cumsum\` using Flux.jl?](https://discourse.julialang.org/t/how-to-create-tracked-cumsum-using-flux-jl/17772)

<div class="topic-metadata">

**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 12\
**Last updated:** [December 1, 2018, 7:35am UTC](https://discourse.julialang.org/t/how-to-create-tracked-cumsum-using-flux-jl/17772 "2018-12-01T07:35:27Z")

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I wanted to create a cumsum of tracked values. How do I do that? I tried the below which failed W = param(rand(12,1)) cumsum(Tracker.data(W), dims = 1) # works cumsum(W, dims = 1) # this fails I got it to work using m…

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## [How to histogram Flux predictions?](https://discourse.julialang.org/t/how-to-histogram-flux-predictions/18194)

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**Author:** [@jstrube](https://discourse.julialang.org/u/jstrube)\
**Replies:** 3\
**Last updated:** [November 30, 2018, 11:29pm UTC](https://discourse.julialang.org/t/how-to-histogram-flux-predictions/18194 "2018-11-30T23:29:23Z")

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I’m training a simple regression network with Flux. I’m still learning about the optimizers, but it seems to work OK. However, when I try to make a histogram of predictions on a new data set, I’m getting m(x\[:,1:4\]) Tra…

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## [Active set and list of (NL) constraints in JuMP](https://discourse.julialang.org/t/active-set-and-list-of-nl-constraints-in-jump/18186)

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**Author:** [@jacob-roth](https://discourse.julialang.org/u/jacob-roth)\
**Replies:** 1\
**Last updated:** [November 30, 2018, 4:10pm UTC](https://discourse.julialang.org/t/active-set-and-list-of-nl-constraints-in-jump/18186 "2018-11-30T16:10:22Z")

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Is there a convenient way to access all of the constraints (including @NLconstraint) in a JuMP (v0.18.4) model? I’ve tried accessing model.linconstr etc, but it doesn’t give the nonlinear constraints. I’d also like to ge…

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## [Advice on numerical integration of a very "sparse" function](https://discourse.julialang.org/t/advice-on-numerical-integration-of-a-very-sparse-function/18176)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 25\
**Last updated:** [November 30, 2018, 2:59pm UTC](https://discourse.julialang.org/t/advice-on-numerical-integration-of-a-very-sparse-function/18176 "2018-11-30T14:59:46Z")

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I have a function that when sampled evenly across its two domains looks something like this: Almost everything is zero… I need to integrate it. I tried HCubature.jl and Cuba.jl but they either returned zero or faile…

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## [Parallel Good Practice](https://discourse.julialang.org/t/parallel-good-practice/17486)

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**Author:** [@Julien](https://discourse.julialang.org/u/Julien)\
**Replies:** 22\
**Last updated:** [November 30, 2018, 2:10pm UTC](https://discourse.julialang.org/t/parallel-good-practice/17486 "2018-11-30T14:10:24Z")

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Hi, I have quite a naive question regarding parallelism in Julia. Let’s say I have a machine with 4 CPUs. I want to fully use my machine and I can easily use 4 workers in parallel for my problem. The manual says: " Le…

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## [Registering jacobians of composite types in AutoGrad.jl](https://discourse.julialang.org/t/registering-jacobians-of-composite-types-in-autograd-jl/18149)

<div class="topic-metadata">

**Author:** [@crinders](https://discourse.julialang.org/u/crinders)\
**Replies:** 2\
**Last updated:** [November 30, 2018, 1:59pm UTC](https://discourse.julialang.org/t/registering-jacobians-of-composite-types-in-autograd-jl/18149 "2018-11-30T13:59:29Z")

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I am posting this question here, because AutoGrad.jl is associated with Knet. I have a derivative of the svd. svd returns an object of type SVD, with components U, Vt, and S. I want to register the derivative with Auto…

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## [Question regarding Query.jl @join implementation](https://discourse.julialang.org/t/question-regarding-query-jl-join-implementation/18145)

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**Author:** [@gbenatt92](https://discourse.julialang.org/u/gbenatt92)\
**Replies:** 1\
**Last updated:** [November 29, 2018, 5:12pm UTC](https://discourse.julialang.org/t/question-regarding-query-jl-join-implementation/18145 "2018-11-29T17:12:11Z")

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Hi! I’ve sent this question over a DM to professor @davidanthoff, but it’s better suited here. Regarding the Query.jl package, I’d like to know what are the implementations of @join and @groupjoin, how efficient they a…

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## [How to avoid re-computing the same matrix in optimisation/JuMP?](https://discourse.julialang.org/t/how-to-avoid-re-computing-the-same-matrix-in-optimisation-jump/17883)

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**Author:** [@Olegg](https://discourse.julialang.org/u/Olegg)\
**Replies:** 3\
**Last updated:** [November 29, 2018, 5:34pm UTC](https://discourse.julialang.org/t/how-to-avoid-re-computing-the-same-matrix-in-optimisation-jump/17883 "2018-11-29T17:34:55Z")

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I have a user-defined nonlinear constraint and its analytical gradient. A major effort is to compute the same matrix in both functions. In the problem below, it’s computed twice; in other problems, up to 2p times for a p…

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## [Elegant way to construct a set of multi-index](https://discourse.julialang.org/t/elegant-way-to-construct-a-set-of-multi-index/18081)

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**Author:** [@OlivierHnt](https://discourse.julialang.org/u/OlivierHnt)\
**Replies:** 19\
**Last updated:** [November 29, 2018, 2:25pm UTC](https://discourse.julialang.org/t/elegant-way-to-construct-a-set-of-multi-index/18081 "2018-11-29T14:25:14Z")

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Good evening, I wish to build an array containing specific multi-index. More precisely, in the 2-D case the multi-index are given by (i, j) where 0 \<= i , j \<= N+1 such that i+j \<= N+1. The way I do it is make a (N+1)x…

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## [No output in Atom plot pane or gui in both julia 0.7 and 1.0](https://discourse.julialang.org/t/no-output-in-atom-plot-pane-or-gui-in-both-julia-0-7-and-1-0/18100)

<div class="topic-metadata">

**Author:** [@martinzh](https://discourse.julialang.org/u/martinzh)\
**Replies:** 9\
**Last updated:** [November 29, 2018, 12:12pm UTC](https://discourse.julialang.org/t/no-output-in-atom-plot-pane-or-gui-in-both-julia-0-7-and-1-0/18100 "2018-11-29T12:12:39Z")

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Hi, with both julia 0.7 and 1.0 I can make graphs from the REPL but whenever I try to do it from Atom, there’s no output in the Plot pane nor I can open the gui windows, neither with GR or PyPlot. However, the graphs ar…

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## [Binary Variable](https://discourse.julialang.org/t/binary-variable/18093)

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**Author:** [@muriloasouza](https://discourse.julialang.org/u/muriloasouza)\
**Replies:** 4\
**Last updated:** [November 29, 2018, 4:52am UTC](https://discourse.julialang.org/t/binary-variable/18093 "2018-11-29T04:52:54Z")

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I got in my problem some binary variable, thats a decision to install or not an equipment in a house. Among a lot of other variables and constraints, my problem is something like this: N = 5; # number of houses @variabl…

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## [JuliaDB Getting Started...with save error](https://discourse.julialang.org/t/juliadb-getting-started-with-save-error/17891)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 6\
**Last updated:** [November 28, 2018, 7:59pm UTC](https://discourse.julialang.org/t/juliadb-getting-started-with-save-error/17891 "2018-11-28T19:59:57Z")

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I am taking my first little steps in JuliaDB. I am planning to follow https://juliadb.org/latest, including the tutorial. I do not only want to access the data, but reduce the loading time relative to .csv . (I have l…

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## [\`Complex{Dual}\` or \`Dual{Complex}\`](https://discourse.julialang.org/t/complex-dual-or-dual-complex/5455)

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**Author:** [@gasagna](https://discourse.julialang.org/u/gasagna)\
**Replies:** 12\
**Last updated:** [November 27, 2018, 5:57am UTC](https://discourse.julialang.org/t/complex-dual-or-dual-complex/5455 "2018-11-27T05:57:37Z")

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TLDR: I think Dual should be \<:Real and that Complex{Dual} leads to more generic code than Dual{Complex}. Hi all, I am toying with mixed complex and dual numbers. My use case is numerical integration of a nonlinear PD…

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## [Saving JUMPArray to JLD or JLD2 file](https://discourse.julialang.org/t/saving-jumparray-to-jld-or-jld2-file/18033)

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**Author:** [@YoungFaithful](https://discourse.julialang.org/u/YoungFaithful)\
**Replies:** 3\
**Last updated:** [November 28, 2018, 4:07am UTC](https://discourse.julialang.org/t/saving-jumparray-to-jld-or-jld2-file/18033 "2018-11-28T04:07:06Z")

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Hi, I’m facing the problem that trying to save a JUMPArray with JLD or JLD2 causes the error that it “cannot write pointers to JLD file”. Is there any way to save an entire JUMPArray to a file without decomposing it into…

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## [Multiprecision arithmetic in CUDA](https://discourse.julialang.org/t/multiprecision-arithmetic-in-cuda/18087)

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**Author:** [@elaine](https://discourse.julialang.org/u/elaine)\
**Replies:** 1\
**Last updated:** [November 28, 2018, 2:17am UTC](https://discourse.julialang.org/t/multiprecision-arithmetic-in-cuda/18087 "2018-11-28T02:17:50Z")

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RE: Compary or something similar Is this already implemented or can it be done in Julia and/or Python ? links to 2018 source code for multiprecision arithmetic in CUDA link to source Campary Purpose is to get multi…

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## [submit a Bug report when using SCS solver](https://discourse.julialang.org/t/submit-a-bug-report-when-using-scs-solver/18080)

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**Author:** [@Ryan](https://discourse.julialang.org/u/Ryan)\
**Replies:** 2\
**Last updated:** [November 28, 2018, 12:45am UTC](https://discourse.julialang.org/t/submit-a-bug-report-when-using-scs-solver/18080 "2018-11-28T00:45:48Z")

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bug report when using SCS solver Please submit a bug report with steps to reproduce this fault, and any error messages that follow (i n their entirety). Thanks. Exception: EXCEPTION\_ACCESS\_VIOLATION at 0x6669d61c – va…

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## [Fastest way to blit images to a window](https://discourse.julialang.org/t/fastest-way-to-blit-images-to-a-window/1406)

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**Author:** [@jtravs](https://discourse.julialang.org/u/jtravs)\
**Replies:** 16\
**Last updated:** [November 27, 2018, 2:32pm UTC](https://discourse.julialang.org/t/fastest-way-to-blit-images-to-a-window/1406 "2018-11-27T14:32:35Z")

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Hi, I’m in the process of writing a laser beam profiler software with Julia. Fo this I am grabbing greyscale images from a scientific camera, that can be up to 4000x3000 pixels, stored as wither UInt8 or UInt16. I now w…

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## [JuliaBox: Package releases and Plotting problem](https://discourse.julialang.org/t/juliabox-package-releases-and-plotting-problem/18046)

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**Author:** [@lwabeke](https://discourse.julialang.org/u/lwabeke)\
**Replies:** 0\
**Last updated:** [November 27, 2018, 7:20am UTC](https://discourse.julialang.org/t/juliabox-package-releases-and-plotting-problem/18046 "2018-11-27T07:20:59Z")

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Hi I’m not sure where to list this properly, because it started with a plotting problem: using Plots with plotlyjs backend doesn’t seem to work on IJulia anymore. I tried a few things on my side (getting master, trying…

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## [UndefVarError: @variable not defined](https://discourse.julialang.org/t/undefvarerror-variable-not-defined/17903)

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**Author:** [@marouane](https://discourse.julialang.org/u/marouane)\
**Replies:** 2\
**Last updated:** [November 27, 2018, 6:57am UTC](https://discourse.julialang.org/t/undefvarerror-variable-not-defined/17903 "2018-11-27T06:57:18Z")

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hi Guys, recently i have been trying to write a code but when i run it it shows me this: “UndefVarError: @variable not defined” this is the entire code: ’ ’ ’ Julia function scan\_maker(A) m = Model(solver=ClpSolver(…

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## [Hessian matrix for standard errors using Optim.jl example](https://discourse.julialang.org/t/hessian-matrix-for-standard-errors-using-optim-jl-example/17996)

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**Author:** [@oizin](https://discourse.julialang.org/u/oizin)\
**Replies:** 1\
**Last updated:** [November 27, 2018, 4:52am UTC](https://discourse.julialang.org/t/hessian-matrix-for-standard-errors-using-optim-jl-example/17996 "2018-11-27T04:52:28Z")

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I’m looking at the maximum likelihood example on the Optim.jl page and trying it on a different likelihood function (truncated normal). I’m running into an issue where the covariance matrix returned using the Optim examp…

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## [Object detection (with ROIs) in Mocha.jl?](https://discourse.julialang.org/t/object-detection-with-rois-in-mocha-jl/18023)

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**Author:** [@ianshmean](https://discourse.julialang.org/u/ianshmean)\
**Replies:** 0\
**Last updated:** [November 26, 2018, 6:27pm UTC](https://discourse.julialang.org/t/object-detection-with-rois-in-mocha-jl/18023 "2018-11-26T18:27:48Z")

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I’m trying to get bounding-box style object detection running through Mocha.jl and wondering if anyone is aware of any work on this front? Mocha has tidy image classification examples, but I haven’t found an object detec…

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## [Constraints in RigidBodyDynamics](https://discourse.julialang.org/t/constraints-in-rigidbodydynamics/18010)

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**Author:** [@RogerP](https://discourse.julialang.org/u/RogerP)\
**Replies:** 2\
**Last updated:** [November 26, 2018, 3:53pm UTC](https://discourse.julialang.org/t/constraints-in-rigidbodydynamics/18010 "2018-11-26T15:53:19Z")

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Is there a way of adding kinematic constraints using RBD? For instance, I have a double-prismatic joint, i.e a telescopic joint, where the inner always moves at twice the speed of the outer. (The two components are huge …

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## [solving convex MINLP problem](https://discourse.julialang.org/t/solving-convex-minlp-problem/18015)

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**Author:** [@Jay\_Dave](https://discourse.julialang.org/u/Jay_Dave)\
**Replies:** 0\
**Last updated:** [November 26, 2018, 2:36pm UTC](https://discourse.julialang.org/t/solving-convex-minlp-problem/18015 "2018-11-26T14:36:19Z")

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Hello, I am using second-order cone relaxation to convert my original non-linear problem. When I solve it using juniper (cplex as mip+ ipopt ), the solved objective is correct but takes longer than solving the non-linea…

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## [Multivariate normality tests](https://discourse.julialang.org/t/multivariate-normality-tests/8384)

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**Author:** [@anriseth](https://discourse.julialang.org/u/anriseth)\
**Replies:** 4\
**Last updated:** [November 26, 2018, 10:04am UTC](https://discourse.julialang.org/t/multivariate-normality-tests/8384 "2018-11-26T10:04:13Z")

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Are there any packages for running multivariate normality tests on data in the Juliaverse? I am looking for something along the lines of the R package MVN

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