# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1096

[Latest](https://discourse.julialang.org/latest.md) · [Categories](https://discourse.julialang.org/categories.md) · [Tags](https://discourse.julialang.org/tags.md)

**Page:** 1097

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## [NLopt :FORCED\_STOP](https://discourse.julialang.org/t/nlopt-forced-stop/47747)

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**Author:** [@danicaratelli](https://discourse.julialang.org/u/danicaratelli)\
**Replies:** 2\
**Last updated:** [March 15, 2022, 8:57am UTC](https://discourse.julialang.org/t/nlopt-forced-stop/47747 "2022-03-15T08:57:19Z")

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Hello, I am trying to get NLopt to work but it just stops immediately and gives :FORCED\_STOP. I tried the following but it looks like the algorithm isn’t even going into \_ff. Any thoughts? Thank you! function ff(x) …

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## [What exactly Flux.destructure does?](https://discourse.julialang.org/t/what-exactly-flux-destructure-does/77402)

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**Author:** [@Avec](https://discourse.julialang.org/u/Avec)\
**Replies:** 6\
**Last updated:** [March 15, 2022, 8:52am UTC](https://discourse.julialang.org/t/what-exactly-flux-destructure-does/77402 "2022-03-15T08:52:19Z")

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Hi all, I built a custom nn model UnetSkipGenerator, trained it and needed to save the results, therefore I used Flux.destructure and saved the parameters it returned. Now I am trying to do some computations with them, …

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## [ODE.jl: PolyCompat not defined](https://discourse.julialang.org/t/ode-jl-polycompat-not-defined/54332)

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**Author:** [@Caio\_Machado](https://discourse.julialang.org/u/Caio_Machado)\
**Replies:** 4\
**Last updated:** [March 15, 2022, 8:31am UTC](https://discourse.julialang.org/t/ode-jl-polycompat-not-defined/54332 "2022-03-15T08:31:01Z")

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Hi all, I am trying to run ODE.jl in Julia 1.5, but I get the following error when loading the package. I have installed Polynomials using Pkg.add(). I know there are better solvers available in DifferentialEquations.jl…

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## [Can NODE be compatible well with Boundary Value Problems?](https://discourse.julialang.org/t/can-node-be-compatible-well-with-boundary-value-problems/77902)

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**Author:** [@YukunYan](https://discourse.julialang.org/u/YukunYan)\
**Replies:** 0\
**Last updated:** [March 15, 2022, 6:58am UTC](https://discourse.julialang.org/t/can-node-be-compatible-well-with-boundary-value-problems/77902 "2022-03-15T06:58:22Z")

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Recently, I have tried to use NODE in BVP to learn the parameter(the code is below). I have found that “DiffEqFlux.sciml\_train” is ok to train while there will be a warning that AD methods failed, using numerical differe…

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## [Startup Speed](https://discourse.julialang.org/t/startup-speed/77893)

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**Author:** [@benj](https://discourse.julialang.org/u/benj)\
**Replies:** 6\
**Last updated:** [March 15, 2022, 6:41am UTC](https://discourse.julialang.org/t/startup-speed/77893 "2022-03-15T06:41:38Z")

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Hello everybody! I’ve been learning Julia and I’ve been loving it!! I’m curious about startup times… I have this super simple code, but I’m baffled at how it take about 13 seconds to start! Also tested it on an i9 sinc…

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## [Agents.jl Question: collecting data in abm\_video](https://discourse.julialang.org/t/agents-jl-question-collecting-data-in-abm-video/77826)

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**Author:** [@codekomali](https://discourse.julialang.org/u/codekomali)\
**Replies:** 4\
**Last updated:** [March 14, 2022, 11:26pm UTC](https://discourse.julialang.org/t/agents-jl-question-collecting-data-in-abm-video/77826 "2022-03-14T23:26:02Z")

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I am new to Julia. I am interested in Agent Based Modeling and planning to use Agents.jl as an alternative to NetLogo. I just finished the first tutorial: Schelling’s segregation. I need some help with the visualisation…

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## [Using Plots not working in Jupiter notebook on apple M1](https://discourse.julialang.org/t/using-plots-not-working-in-jupiter-notebook-on-apple-m1/77896)

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**Author:** [@barfi](https://discourse.julialang.org/u/barfi)\
**Replies:** 0\
**Last updated:** [March 14, 2022, 10:13pm UTC](https://discourse.julialang.org/t/using-plots-not-working-in-jupiter-notebook-on-apple-m1/77896 "2022-03-14T22:13:42Z")

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Plots works fine in terminal mode but gets stuck at using Plots in Jupiter notebook on apple M1. Updated everything . using Julia 1.72

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## [Performance of array of arrays vs. dictionaries when accessing and manipulating data structures](https://discourse.julialang.org/t/performance-of-array-of-arrays-vs-dictionaries-when-accessing-and-manipulating-data-structures/77860)

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**Author:** [@Christian\_Brunbjerg](https://discourse.julialang.org/u/Christian_Brunbjerg)\
**Replies:** 5\
**Last updated:** [March 14, 2022, 9:36pm UTC](https://discourse.julialang.org/t/performance-of-array-of-arrays-vs-dictionaries-when-accessing-and-manipulating-data-structures/77860 "2022-03-14T21:36:12Z")

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I here have two different structs that represent the same data. The main objective is to achieve as fast as possible performance. #Using array of arrays representation struct Route\_array Station::Vector{Int64} T…

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## [How to best handle these exceptions in FOC of maximization?](https://discourse.julialang.org/t/how-to-best-handle-these-exceptions-in-foc-of-maximization/77575)

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**Author:** [@amrods](https://discourse.julialang.org/u/amrods)\
**Replies:** 1\
**Last updated:** [March 14, 2022, 10:03pm UTC](https://discourse.julialang.org/t/how-to-best-handle-these-exceptions-in-foc-of-maximization/77575 "2022-03-14T22:03:19Z")

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I’m trying to maximize a function f(t\_1, t\_2) for which the first order conditions yield 2 equations depending on some conditions. The FOCs divide the plane into 3 regions, where t\_1 \> t\_2, where t\_1 \< t\_2, and where t\_1…

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## [Indexing \`OrderedDict\`s by index instead of key](https://discourse.julialang.org/t/indexing-ordereddict-s-by-index-instead-of-key/77846)

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**Author:** [@Jollywatt](https://discourse.julialang.org/u/Jollywatt)\
**Replies:** 3\
**Last updated:** [March 14, 2022, 9:11pm UTC](https://discourse.julialang.org/t/indexing-ordereddict-s-by-index-instead-of-key/77846 "2022-03-14T21:11:53Z")

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One can access values of OrderedDicts by their index by exposing the internal vals field, like so: julia\> od = sort(Dict('a'=\>'A', 'b'=\>'B')) OrderedCollections.OrderedDict{Char, Char} with 2 entries: 'a' =\> 'A' 'b'…

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## [Hypothesis testing in Julia](https://discourse.julialang.org/t/hypothesis-testing-in-julia/77784)

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**Author:** [@mihrits](https://discourse.julialang.org/u/mihrits)\
**Replies:** 4\
**Last updated:** [March 14, 2022, 8:29pm UTC](https://discourse.julialang.org/t/hypothesis-testing-in-julia/77784 "2022-03-14T20:29:18Z")

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I am taking a statistical data science course that is taught using R, and I am trying to replicate all the practical things in Julia. As we are doing quite basic stuff, mostly everything has been quite straightforward an…

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## [How to build a Poincaré section for a 6th order system?](https://discourse.julialang.org/t/how-to-build-a-poincare-section-for-a-6th-order-system/77694)

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**Author:** [@egor](https://discourse.julialang.org/u/egor)\
**Replies:** 6\
**Last updated:** [March 14, 2022, 7:42pm UTC](https://discourse.julialang.org/t/how-to-build-a-poincare-section-for-a-6th-order-system/77694 "2022-03-14T19:42:20Z")

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Hello everyone, I want to plot the Poincaré section for the system: Following the example of this tutorial, I wrote the following code: plane = (3, 0.0) fig = Figure(resolution = (600,300)) axx = Axis(fig\[1,1\]; xla…

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## [How to store functions in a structure in a proper way?](https://discourse.julialang.org/t/how-to-store-functions-in-a-structure-in-a-proper-way/77887)

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**Author:** [@denshd](https://discourse.julialang.org/u/denshd)\
**Replies:** 3\
**Last updated:** [March 14, 2022, 7:32pm UTC](https://discourse.julialang.org/t/how-to-store-functions-in-a-structure-in-a-proper-way/77887 "2022-03-14T19:32:51Z")

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Hello! I want to create a structure that stores (besides other data) some functions. It is convinient to store them together in a one structure. But consider the following code (MWE): using BenchmarkTools struct Foo …

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## [Help in sum columns](https://discourse.julialang.org/t/help-in-sum-columns/77883)

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**Author:** [@folleyz](https://discourse.julialang.org/u/folleyz)\
**Replies:** 11\
**Last updated:** [March 14, 2022, 7:16pm UTC](https://discourse.julialang.org/t/help-in-sum-columns/77883 "2022-03-14T19:16:13Z")

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Hi everybody! I’m new in Julia and need a simple help. I want to sum some columns of my dataframe and input that sum in a new column, but i’m trying with this and are not working. colunasSum = \[:CancIncorreto,:DifColet…

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## [How to take the derivative of a function?](https://discourse.julialang.org/t/how-to-take-the-derivative-of-a-function/77885)

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**Author:** [@CentraCep](https://discourse.julialang.org/u/CentraCep)\
**Replies:** 3\
**Last updated:** [March 14, 2022, 6:32pm UTC](https://discourse.julialang.org/t/how-to-take-the-derivative-of-a-function/77885 "2022-03-14T18:32:13Z")

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Let’s say I have a function like this: T = 10^6 η = 10^9\*T^(-3/2) x = range(-10, 10, step=1) t = \[0, 1, 2, 4\] B\_z(x, t) = @. erf(x/sqrt(4\*η\*t)) I wanto differentiate B\_z with respect to x and assign it to a new funct…

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## [How to check whether profiling is supported](https://discourse.julialang.org/t/how-to-check-whether-profiling-is-supported/77882)

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**Author:** [@Uroc327](https://discourse.julialang.org/u/Uroc327)\
**Replies:** 0\
**Last updated:** [March 14, 2022, 5:33pm UTC](https://discourse.julialang.org/t/how-to-check-whether-profiling-is-supported/77882 "2022-03-14T17:33:10Z")

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How can I check whether a julia binary was built with USE\_PERF\_JITEVENTS=1? It seems to be default on linux platforms, but is there any way to query this? I wonder if I have to build julia from source for profiling or i…

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## [Plot lines not appearing](https://discourse.julialang.org/t/plot-lines-not-appearing/77839)

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**Author:** [@CentraCep](https://discourse.julialang.org/u/CentraCep)\
**Replies:** 3\
**Last updated:** [March 14, 2022, 5:25pm UTC](https://discourse.julialang.org/t/plot-lines-not-appearing/77839 "2022-03-14T17:25:11Z")

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My goal is to replicate a plot similar to this one: Although this is a physics problem. I am basically plotting and erf() function. Here is how my code is currently set up right now. using SpecialFunctions, Plots T…

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## [How to implement custom weight initialization in Flux?](https://discourse.julialang.org/t/how-to-implement-custom-weight-initialization-in-flux/77876)

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**Author:** [@DeepQ](https://discourse.julialang.org/u/DeepQ)\
**Replies:** 1\
**Last updated:** [March 14, 2022, 5:15pm UTC](https://discourse.julialang.org/t/how-to-implement-custom-weight-initialization-in-flux/77876 "2022-03-14T17:15:21Z")

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How could I define custom weight initialization in Flux? The solution should be clean. Documentation is confusing. Should I define the Dense layer from scratch?

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## [Function call on STDOUT](https://discourse.julialang.org/t/function-call-on-stdout/77858)

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**Author:** [@FedeClaudi](https://discourse.julialang.org/u/FedeClaudi)\
**Replies:** 12\
**Last updated:** [March 14, 2022, 5:05pm UTC](https://discourse.julialang.org/t/function-call-on-stdout/77858 "2022-03-14T17:05:08Z")

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Hello everyone. Let me describe my situation. In Term I’m working on a progress bar feature. It looks like this: The way the bar display is updated is by using ANSI codes to erase the last line printed out in the …

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## [A parametric-type related crash on Julia 1.7+](https://discourse.julialang.org/t/a-parametric-type-related-crash-on-julia-1-7/77844)

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**Author:** [@frankwswang](https://discourse.julialang.org/u/frankwswang)\
**Replies:** 3\
**Last updated:** [March 14, 2022, 4:49pm UTC](https://discourse.julialang.org/t/a-parametric-type-related-crash-on-julia-1-7/77844 "2022-03-14T16:49:37Z")

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I discovered a very strange crash scenario while developing my package. It seems to only happen on Julia 1.7+. For example, 1.6 runs perfectly well. It took me some time to create this “MWE” from my code base and I hope …

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## [How to record loss during training with Flux.jl?](https://discourse.julialang.org/t/how-to-record-loss-during-training-with-flux-jl/77877)

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**Author:** [@TheLateKronos](https://discourse.julialang.org/u/TheLateKronos)\
**Replies:** 1\
**Last updated:** [March 14, 2022, 4:35pm UTC](https://discourse.julialang.org/t/how-to-record-loss-during-training-with-flux-jl/77877 "2022-03-14T16:35:05Z")

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I want to record the training-loss, along with the test-loss, during a training process. I have to compute the test-loss seperatly from the training process, but I am thinking that I should be able to hook into the train…

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## [Dealing with non-positive definite matrices in Cholesky decomposition: R vs. Julia](https://discourse.julialang.org/t/dealing-with-non-positive-definite-matrices-in-cholesky-decomposition-r-vs-julia/77869)

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**Author:** [@Christopher\_Fisher](https://discourse.julialang.org/u/Christopher_Fisher)\
**Replies:** 4\
**Last updated:** [March 14, 2022, 4:10pm UTC](https://discourse.julialang.org/t/dealing-with-non-positive-definite-matrices-in-cholesky-decomposition-r-vs-julia/77869 "2022-03-14T16:10:56Z")

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Hi all, While porting some R code into Julia, I have encountered many cases where cholesky in Julia returns an error because the matrix is not positive definite. However, in R, I do not run into these cases. I was wonde…

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## [Juniper behaviour: No incumbent when MIP feasible?](https://discourse.julialang.org/t/juniper-behaviour-no-incumbent-when-mip-feasible/77785)

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**Author:** [@ecyrb](https://discourse.julialang.org/u/ecyrb)\
**Replies:** 3\
**Last updated:** [March 14, 2022, 3:41pm UTC](https://discourse.julialang.org/t/juniper-behaviour-no-incumbent-when-mip-feasible/77785 "2022-03-14T15:41:33Z")

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I’m getting some unintuitive behaviour with Juniper (HiGHS & Ipopt). HiGHS is finding a solution that satisfies the constraints, but beyond that an incumbent solution won’t be reported and Juniper will time-out at an inf…

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## [Does locally compiled Julia emit faster code?](https://discourse.julialang.org/t/does-locally-compiled-julia-emit-faster-code/77838)

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**Author:** [@Lewis\_Hein](https://discourse.julialang.org/u/Lewis_Hein)\
**Replies:** 1\
**Last updated:** [March 14, 2022, 3:06pm UTC](https://discourse.julialang.org/t/does-locally-compiled-julia-emit-faster-code/77838 "2022-03-14T15:06:27Z")

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I’m working on a reasonably high-end platform (Intel Xeon E5). Will a generic binary of julia be able to leverage all the various optimizations of this CPU when compiling Julia code? Or do I need to compile from source l…

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## [Can we change the Julia help from bottom-up to top-down?](https://discourse.julialang.org/t/can-we-change-the-julia-help-from-bottom-up-to-top-down/77866)

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**Author:** [@ZdM87](https://discourse.julialang.org/u/ZdM87)\
**Replies:** 7\
**Last updated:** [March 14, 2022, 2:47pm UTC](https://discourse.julialang.org/t/can-we-change-the-julia-help-from-bottom-up-to-top-down/77866 "2022-03-14T14:47:56Z")

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When you type ? in Julia and then type \<something\>, you get all the help information about \<something\> but if this information does not fit in the screen, you will get the tail of the information (like in a bottom-up vie…

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## [Random access to rows of a table](https://discourse.julialang.org/t/random-access-to-rows-of-a-table/77386)

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**Author:** [@ablaom](https://discourse.julialang.org/u/ablaom)\
**Replies:** 27\
**Last updated:** [March 14, 2022, 2:06pm UTC](https://discourse.julialang.org/t/random-access-to-rows-of-a-table/77386 "2022-03-14T14:06:59Z")

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I’d like to see certain enhancements to the tabular data ecosystem, and this post is an appeal to maintainers of table-providing packages (eg, DataFrames) to articulate the form they should like these to take, or give ot…

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## [Generate an array of matrices](https://discourse.julialang.org/t/generate-an-array-of-matrices/77798)

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**Author:** [@jisutich](https://discourse.julialang.org/u/jisutich)\
**Replies:** 12\
**Last updated:** [March 14, 2022, 1:45pm UTC](https://discourse.julialang.org/t/generate-an-array-of-matrices/77798 "2022-03-14T13:45:03Z")

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Hi I want to generate an array A in which each element is a 2\\times 2 matrix. And I want to initialize this array such that each element is \[1/2 0; 0 1/2\]. Later I want to replace some element by different matrices like A…

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## [How to get the state of a dynamic system from lyapunovspectrum?](https://discourse.julialang.org/t/how-to-get-the-state-of-a-dynamic-system-from-lyapunovspectrum/77863)

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**Author:** [@egor](https://discourse.julialang.org/u/egor)\
**Replies:** 0\
**Last updated:** [March 14, 2022, 12:26pm UTC](https://discourse.julialang.org/t/how-to-get-the-state-of-a-dynamic-system-from-lyapunovspectrum/77863 "2022-03-14T12:26:54Z")

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Hello everyone, I am writing a code for calculating the Lyapunov indicators of the system: ks = 0.0:0.0001:1.0; λs = zeros(length(ks), 6) for (i, k) in enumerate(ks) set\_parameter!(ds, 14, k) λs\[i, :\] .= lyapuno…

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## [Error GC failed post updating environment](https://discourse.julialang.org/t/error-gc-failed-post-updating-environment/77817)

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**Author:** [@yewalenikhil65](https://discourse.julialang.org/u/yewalenikhil65)\
**Replies:** 3\
**Last updated:** [March 14, 2022, 10:42am UTC](https://discourse.julialang.org/t/error-gc-failed-post-updating-environment/77817 "2022-03-14T10:42:36Z")

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error GC failed post updating environment(local environment as well as main julia environments) how do i fix this ? Precompiling project... 46 dependencies successfully precompiled in 650 seconds (332 already precomp…

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## [Research Software Engineer at Netherlands eScience Center](https://discourse.julialang.org/t/research-software-engineer-at-netherlands-escience-center/77857)

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**Author:** [@abelsiqueira](https://discourse.julialang.org/u/abelsiqueira)\
**Replies:** 0\
**Last updated:** [March 14, 2022, 10:33am UTC](https://discourse.julialang.org/t/research-software-engineer-at-netherlands-escience-center/77857 "2022-03-14T10:33:10Z")

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TL;DR: https://www.esciencecenter.nl/careers/research-software-engineer-software-impact-team/ We have opened a position (maybe more) at the Netherlands eScience Center for an RSE (https://society-rse.org) working with t…

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