# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=499

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**Page:** 500

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## [Hessenberg factorization](https://discourse.julialang.org/t/hessenberg-factorization/20125)

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**Author:** [@olof3](https://discourse.julialang.org/u/olof3)\
**Replies:** 2\
**Last updated:** [April 27, 2019, 9:27pm UTC](https://discourse.julialang.org/t/hessenberg-factorization/20125 "2019-04-27T21:27:56Z")

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Hello, To compute the frequency response of a linear system \\dot{x} = Ax + Bu y = Cx where A is a square matrix, one should compute G(s) = C(sI - A)\\backslash B for several complex values s. This can be do…

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## [How to surface plot with Makie?](https://discourse.julialang.org/t/how-to-surface-plot-with-makie/23457)

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**Author:** [@cserteGT3](https://discourse.julialang.org/u/cserteGT3)\
**Replies:** 2\
**Last updated:** [April 27, 2019, 9:17pm UTC](https://discourse.julialang.org/t/how-to-surface-plot-with-makie/23457 "2019-04-27T21:17:26Z")

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I’m trying to create a surface plot of a torus. Starting from the examples, I’ve created this: # let's call this mwe.jl using Makie using StaticArrays: SVector function tori(R, r, lR, lr) @assert R \> r "Ring tori, …

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## [Reservoir computing or echo state networks in Flux.jl or Knet.jl](https://discourse.julialang.org/t/reservoir-computing-or-echo-state-networks-in-flux-jl-or-knet-jl/16466)

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**Author:** [@John\_Gibson](https://discourse.julialang.org/u/John_Gibson)\
**Replies:** 5\
**Last updated:** [April 27, 2019, 7:59pm UTC](https://discourse.julialang.org/t/reservoir-computing-or-echo-state-networks-in-flux-jl-or-knet-jl/16466 "2019-04-27T19:59:24Z")

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Can any of the Julia machine learning frameworks do reservoir computing or echo state computing? Are there examples how to configure Flux.jl or Knet.jl to do either of these on a simple problem? As far as I understand i…

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## [How can I draw a plot with Logarithmic scales in Juliabox?](https://discourse.julialang.org/t/how-can-i-draw-a-plot-with-logarithmic-scales-in-juliabox/23577)

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**Author:** [@PP\_PAN](https://discourse.julialang.org/u/PP_PAN)\
**Replies:** 1\
**Last updated:** [April 27, 2019, 7:03pm UTC](https://discourse.julialang.org/t/how-can-i-draw-a-plot-with-logarithmic-scales-in-juliabox/23577 "2019-04-27T19:03:42Z")

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## [Creating a COM connection](https://discourse.julialang.org/t/creating-a-com-connection/23570)

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**Author:** [@FrancisKing](https://discourse.julialang.org/u/FrancisKing)\
**Replies:** 1\
**Last updated:** [April 26, 2019, 9:44pm UTC](https://discourse.julialang.org/t/creating-a-com-connection/23570 "2019-04-26T21:44:07Z")

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Hello. Since Julia is able to do all kinds of things, I was wondering if it can also do this. In Python, VBA, and C# I can connect to COM enabled software such as Microsoft Office and transport planning tools such as S…

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## [Binding something to juliaGPU](https://discourse.julialang.org/t/binding-something-to-juliagpu/23508)

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**Author:** [@Dragon20180618](https://discourse.julialang.org/u/Dragon20180618)\
**Replies:** 2\
**Last updated:** [April 25, 2019, 2:55pm UTC](https://discourse.julialang.org/t/binding-something-to-juliagpu/23508 "2019-04-25T14:55:49Z")

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I want to binding MAGMA to juliaGPU. Create such binding by simply calling its C API via ccall. By binding this to the JuliaGPU ecosystem. But I don’t know how to write codes about that. I need some help.

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## [Makie GL minimum graphics requirements](https://discourse.julialang.org/t/makie-gl-minimum-graphics-requirements/23499)

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**Author:** [@timmm](https://discourse.julialang.org/u/timmm)\
**Replies:** 6\
**Last updated:** [April 25, 2019, 1:14pm UTC](https://discourse.julialang.org/t/makie-gl-minimum-graphics-requirements/23499 "2019-04-25T13:14:02Z")

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I have Makie running on my desktop PC (its great) but cant get it working on my laptop. What are the minimum graphics card requirements for OPENGL in Makie? When I check my card using Open GL Extensions Viewer I get the…

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## [Query.jl: how to filter on derived quantities of a group?](https://discourse.julialang.org/t/query-jl-how-to-filter-on-derived-quantities-of-a-group/23486)

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**Author:** [@gajomi](https://discourse.julialang.org/u/gajomi)\
**Replies:** 3\
**Last updated:** [April 24, 2019, 10:54pm UTC](https://discourse.julialang.org/t/query-jl-how-to-filter-on-derived-quantities-of-a-group/23486 "2019-04-24T22:54:33Z")

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I am having a hard time trying to figure out how to filter by a derived quantity of a group using either the standalone or linq syntax. For example, I might want to group by some column then select only rows in that grou…

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## [Query.@join with repeated names](https://discourse.julialang.org/t/query-join-with-repeated-names/23474)

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**Author:** [@heliosdrm](https://discourse.julialang.org/u/heliosdrm)\
**Replies:** 1\
**Last updated:** [April 24, 2019, 5:39pm UTC](https://discourse.julialang.org/t/query-join-with-repeated-names/23474 "2019-04-24T17:39:04Z")

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Say I have this: julia\> df1 = DataFrame(id=\[1,2,3,4\], a=\[1.,2.,3.,4.\]) 4×2 DataFrame │ Row │ id │ a │ │ │ Int64 │ Float64 │ ├─────┼───────┼─────────┤ │ 1 │ 1 │ 1.0 │ │ 2 │ 2 │ 2.0 │ │ 3 …

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## [Practice JuMP problem - scheduling LP questions](https://discourse.julialang.org/t/practice-jump-problem-scheduling-lp-questions/23390)

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**Author:** [@Crghilardi](https://discourse.julialang.org/u/Crghilardi)\
**Replies:** 8\
**Last updated:** [April 24, 2019, 1:53pm UTC](https://discourse.julialang.org/t/practice-jump-problem-scheduling-lp-questions/23390 "2019-04-24T13:53:23Z")

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I am practising by translating a python LP scheduling example using JuMP. I have been using a combination of the SteelT3 example and some older notebooks I found as guiding references, but have not been able to get ever…

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## [Annotate! on pyplot backend not working properly](https://discourse.julialang.org/t/annotate-on-pyplot-backend-not-working-properly/23471)

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**Author:** [@lazarusA](https://discourse.julialang.org/u/lazarusA)\
**Replies:** 0\
**Last updated:** [April 24, 2019, 1:17pm UTC](https://discourse.julialang.org/t/annotate-on-pyplot-backend-not-working-properly/23471 "2019-04-24T13:17:20Z")

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Something is not right with annotate and the pyplot backend. If I use gr() this shows properly my output on the other hand pyplot it’s not. I would use gr() but the file size output is to big, that’s why I need …

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## [Removing variable types from a Dataframe in weave report?](https://discourse.julialang.org/t/removing-variable-types-from-a-dataframe-in-weave-report/23273)

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**Author:** [@LasseKatten](https://discourse.julialang.org/u/LasseKatten)\
**Replies:** 0\
**Last updated:** [April 18, 2019, 11:36am UTC](https://discourse.julialang.org/t/removing-variable-types-from-a-dataframe-in-weave-report/23273 "2019-04-18T11:36:31Z")

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Hello Following the example provided at this page, I’ve managed to weave it into an html document using the following line using Weave; weave(“weave\_test.jmd”, out\_path = :pwd, doctype = “md2html”) The problem, howe…

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## [How fast is binary reading capabilities in Julia compared with other languages?](https://discourse.julialang.org/t/how-fast-is-binary-reading-capabilities-in-julia-compared-with-other-languages/23401)

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**Author:** [@Ahmed\_Salih](https://discourse.julialang.org/u/Ahmed_Salih)\
**Replies:** 11\
**Last updated:** [April 23, 2019, 6:18pm UTC](https://discourse.julialang.org/t/how-fast-is-binary-reading-capabilities-in-julia-compared-with-other-languages/23401 "2019-04-23T18:18:14Z")

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I am specifically talking about reading binary files, so nothing with CSV. Is Julia one of the fastest in this respect or would I still see much better performance by making it in c++? Currently I am for an example abl…

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## [Problem visualizing x-axis' ticks on a plot](https://discourse.julialang.org/t/problem-visualizing-x-axis-ticks-on-a-plot/23395)

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**Author:** [@ale](https://discourse.julialang.org/u/ale)\
**Replies:** 4\
**Last updated:** [April 23, 2019, 4:35pm UTC](https://discourse.julialang.org/t/problem-visualizing-x-axis-ticks-on-a-plot/23395 "2019-04-23T16:35:02Z")

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Hi everyone, I am plotting a graph by using: using Plots pyplot() ... And I obtain the following: Which is fine, apart from how the x-axis ticks are displayed. What can that be due to? Maybe too large values? The…

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## [Develop a package to look up timezone based on latitude/longitude data?](https://discourse.julialang.org/t/develop-a-package-to-look-up-timezone-based-on-latitude-longitude-data/23443)

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**Author:** [@xue35](https://discourse.julialang.org/u/xue35)\
**Replies:** 1\
**Last updated:** [April 23, 2019, 2:08pm UTC](https://discourse.julialang.org/t/develop-a-package-to-look-up-timezone-based-on-latitude-longitude-data/23443 "2019-04-23T14:08:09Z")

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Hello, I want to check if anyone is interested in developing a package to determin timezone based on geolocation (latitude/longitude)? Of course there are some more to consider like DST… Cheers,

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## [Robotics - SensorFeatureTracking](https://discourse.julialang.org/t/robotics-sensorfeaturetracking/23436)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 2\
**Last updated:** [April 23, 2019, 12:32pm UTC](https://discourse.julialang.org/t/robotics-sensorfeaturetracking/23436 "2019-04-23T12:32:30Z")

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The package in Julia Robotics for feature tracking seems to be a bit neglected. Is there anything equivalent which is more active?

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## [Plots: adding to plot doesn't preserve series style](https://discourse.julialang.org/t/plots-adding-to-plot-doesnt-preserve-series-style/23417)

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**Author:** [@PeteS](https://discourse.julialang.org/u/PeteS)\
**Replies:** 0\
**Last updated:** [April 22, 2019, 6:41pm UTC](https://discourse.julialang.org/t/plots-adding-to-plot-doesnt-preserve-series-style/23417 "2019-04-22T18:41:46Z")

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Hello, new to Julia so I may have missed something here. I’m creating a line plot, setting the style as step, then adding points in a loop … to mimic the output of a simulation. When the points are added the style reve…

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## [Stop optimization problem when the objective is negative?](https://discourse.julialang.org/t/stop-optimization-problem-when-the-objective-is-negative/23330)

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**Author:** [@longemen3000](https://discourse.julialang.org/u/longemen3000)\
**Replies:** 4\
**Last updated:** [April 21, 2019, 11:10pm UTC](https://discourse.julialang.org/t/stop-optimization-problem-when-the-objective-is-negative/23330 "2019-04-21T23:10:55Z")

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i have a Helmholtz function, that needs to be optimized, but i need to stop the optimization algorithm if the value of the objective function is negative, any ideas?, im using Optim.jl using Optim N = 10 c = rand(N) .- …

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## [Implementing multiple skip connections in Flux.ml?](https://discourse.julialang.org/t/implementing-multiple-skip-connections-in-flux-ml/23378)

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**Author:** [@dopamine](https://discourse.julialang.org/u/dopamine)\
**Replies:** 0\
**Last updated:** [April 21, 2019, 6:09pm UTC](https://discourse.julialang.org/t/implementing-multiple-skip-connections-in-flux-ml/23378 "2019-04-21T18:09:42Z")

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Hello, I’m trying to implement u-net (see here for architecture) like architecture using Flux.ml, which requires multiple skip connections. What is the most efficient way to implement multiple skip connections? I’ve see…

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## [Webscokets with Julia](https://discourse.julialang.org/t/webscokets-with-julia/23372)

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**Author:** [@KirillGerke](https://discourse.julialang.org/u/KirillGerke)\
**Replies:** 0\
**Last updated:** [April 21, 2019, 3:22pm UTC](https://discourse.julialang.org/t/webscokets-with-julia/23372 "2019-04-21T15:22:46Z")

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Hello All, I am trying to implement something like a chat server and/or fast computation progress exchange from Julia code (to login from anywhere with the browser). The first search gave me WebSockets.jl and HTTP.jl fo…

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## [Problems to close plots with StatsPlots library](https://discourse.julialang.org/t/problems-to-close-plots-with-statsplots-library/23350)

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**Author:** [@Alessandro\_Vivas](https://discourse.julialang.org/u/Alessandro_Vivas)\
**Replies:** 2\
**Last updated:** [April 21, 2019, 12:39pm UTC](https://discourse.julialang.org/t/problems-to-close-plots-with-statsplots-library/23350 "2019-04-21T12:39:57Z")

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I am using the StatsPlots library but the plots are getting overwritten. I tried to use clf() function but doen’t work. x=vcat(V\[:D1\], V\[:D2\], V\[:D3\] ,V\[:D4\], V\[:D5\] ,V\[:D6\]) p1=StatsPlots.ea\_histogram(x,title=“NumOcor…

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## [StatsBase, sampling without "putting back"](https://discourse.julialang.org/t/statsbase-sampling-without-putting-back/23367)

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**Author:** [@Gunter\_Faes](https://discourse.julialang.org/u/Gunter_Faes)\
**Replies:** 2\
**Last updated:** [April 21, 2019, 10:28am UTC](https://discourse.julialang.org/t/statsbase-sampling-without-putting-back/23367 "2019-04-21T10:28:39Z")

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Hello, Using the StatsBase package, it is possible to take samples using various procedures. Seems to me, but only with “put back”. This means that the same sample is taken several times. Is there a parameter or a proc…

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## [ForwardDiff errors when evaluating type: Array{Float64}](https://discourse.julialang.org/t/forwarddiff-errors-when-evaluating-type-array-float64/23361)

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**Author:** [@GregVernon](https://discourse.julialang.org/u/GregVernon)\
**Replies:** 2\
**Last updated:** [April 21, 2019, 5:31am UTC](https://discourse.julialang.org/t/forwarddiff-errors-when-evaluating-type-array-float64/23361 "2019-04-21T05:31:30Z")

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My questions are asked at the bottom of this post, but their background is developed through this post - which is perhaps a bit pedantic. I’m writing a p-method FEM code. Instead of explicitly coding high-order shape f…

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## [Time-dependent events in ODE](https://discourse.julialang.org/t/time-dependent-events-in-ode/14951)

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**Author:** [@hellopascal](https://discourse.julialang.org/u/hellopascal)\
**Replies:** 14\
**Last updated:** [April 20, 2019, 2:52am UTC](https://discourse.julialang.org/t/time-dependent-events-in-ode/14951 "2019-04-20T02:52:20Z")

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I recently started with Julia and wanted to implement one of my usual problems - implement time-depended events. For now I have: # Packages using Plots using DifferentialEquations # Parameters k21 = 0.14\*24 k12 = 0.06…

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## [Remote access arrays in a numerical grid](https://discourse.julialang.org/t/remote-access-arrays-in-a-numerical-grid/23281)

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**Author:** [@ArjunNarayanan](https://discourse.julialang.org/u/ArjunNarayanan)\
**Replies:** 6\
**Last updated:** [April 19, 2019, 11:05pm UTC](https://discourse.julialang.org/t/remote-access-arrays-in-a-numerical-grid/23281 "2019-04-19T23:05:36Z")

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I am learning the distributed computing capabilities of Julia as applied to numerical methods. I am currently interested in learning how to use the standard Distributed capabilities rather than solutions from MPI.jl and …

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## [Julia Implementation of Transformer Neural Network Model](https://discourse.julialang.org/t/julia-implementation-of-transformer-neural-network-model/23282)

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**Author:** [@mjb](https://discourse.julialang.org/u/mjb)\
**Replies:** 3\
**Last updated:** [April 19, 2019, 6:08pm UTC](https://discourse.julialang.org/t/julia-implementation-of-transformer-neural-network-model/23282 "2019-04-19T18:08:49Z")

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I developed an implementation of a Transformer model using Flux 0.8.2. The implementation is based on The Annotated Transformer If this is of interest, I am happy to contribute it (I don’t know how or where the best pla…

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## [Project PyCX in Julia](https://discourse.julialang.org/t/project-pycx-in-julia/23305)

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**Author:** [@sbacelar](https://discourse.julialang.org/u/sbacelar)\
**Replies:** 2\
**Last updated:** [April 19, 2019, 1:57pm UTC](https://discourse.julialang.org/t/project-pycx-in-julia/23305 "2019-04-19T13:57:45Z")

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Just a suggestion by a Complexity Science student and a Julia fan (not knowing enough): to build a Julia version of Project PyCX in Julia. Hiroki Sayama, Introduction to the Modeling and Analysis of Complex Systems uses…

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## [Nonlinear optimization using MathOptInterface - examples/learning](https://discourse.julialang.org/t/nonlinear-optimization-using-mathoptinterface-examples-learning/23261)

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**Author:** [@cosmia](https://discourse.julialang.org/u/cosmia)\
**Replies:** 8\
**Last updated:** [April 19, 2019, 5:22am UTC](https://discourse.julialang.org/t/nonlinear-optimization-using-mathoptinterface-examples-learning/23261 "2019-04-19T05:22:25Z")

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(sorry for the long post) Hi all, For the past 6 months or so, on and off, I’ve been trying to estimate a finite horizon dynamic discrete choice model. If you are not familiar with it, suffices to say that for every st…

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## [Julia motivation for machine learning](https://discourse.julialang.org/t/julia-motivation-for-machine-learning/23259)

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**Author:** [@tk3369](https://discourse.julialang.org/u/tk3369)\
**Replies:** 6\
**Last updated:** [April 18, 2019, 1:29pm UTC](https://discourse.julialang.org/t/julia-motivation-for-machine-learning/23259 "2019-04-18T13:29:30Z")

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Out of curiosity, in the domain of machine learning and NLP - what would be the reasons to choose julia over python? What would be the reasons to choose python over julia? What are some of the gaps in julia as c…

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## [Signal (11): Segmentation fault: 11 with DifferentialEquations.jl](https://discourse.julialang.org/t/signal-11-segmentation-fault-11-with-differentialequations-jl/23264)

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**Author:** [@boutor2](https://discourse.julialang.org/u/boutor2)\
**Replies:** 2\
**Last updated:** [April 18, 2019, 11:22am UTC](https://discourse.julialang.org/t/signal-11-segmentation-fault-11-with-differentialequations-jl/23264 "2019-04-18T11:22:48Z")

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Hello there, It seems there is a bug with DifferentialEquations.jl when solving for large systems of ODEs. I tried to make the simplest example to obtain the error: using DifferentialEquations function f(du,u,p,t) …

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