# Latest

**URL:** https://discourse.julialang.org/latest.md?page=533

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

**Page:** 534

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## [Two arrows](https://discourse.julialang.org/t/two-arrows/107453)

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**Author:** [@vladdez](https://discourse.julialang.org/u/vladdez)\
**Replies:** 4\
**Last updated:** [December 11, 2023, 4:51pm UTC](https://discourse.julialang.org/t/two-arrows/107453 "2023-12-11T16:51:55Z")

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Can anyone please show how to create a simplest plot with two arrows using Makie.arrow? Documentation here arrows · Makie is written at really advance level.

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## [Help on reported JET issue when using StaticArrays](https://discourse.julialang.org/t/help-on-reported-jet-issue-when-using-staticarrays/107444)

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**Author:** [@mestinso](https://discourse.julialang.org/u/mestinso)\
**Replies:** 3\
**Last updated:** [December 11, 2023, 4:33pm UTC](https://discourse.julialang.org/t/help-on-reported-jet-issue-when-using-staticarrays/107444 "2023-12-11T16:33:18Z")

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I am doing some analysis of some of my code using JET.jl. When I use StaticArrays in the following way (below is a MWE), report\_call from JET is unhappy: a=MVector(1,2,3,4,5) b=MVector(6,7,8,9,10) @report\_call b\[a.==2\]…

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## [Regression in Precompile time with 1.10.0-rc2 compared to the rc1 version](https://discourse.julialang.org/t/regression-in-precompile-time-with-1-10-0-rc2-compared-to-the-rc1-version/107324)

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**Author:** [@svretina](https://discourse.julialang.org/u/svretina)\
**Replies:** 6\
**Last updated:** [December 11, 2023, 4:31pm UTC](https://discourse.julialang.org/t/regression-in-precompile-time-with-1-10-0-rc2-compared-to-the-rc1-version/107324 "2023-12-11T16:31:25Z")

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I recently upgraded to the 1.10.0-rc2 version and I see a regression in the precompilation time of my package. There is no option in juliaup to revert back to rc1. Do you also see this with the rc2 version?

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## [Double Pendulum Animation with Julia](https://discourse.julialang.org/t/double-pendulum-animation-with-julia/89142)

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**Author:** [@Freya\_the\_Goddess](https://discourse.julialang.org/u/Freya_the_Goddess)\
**Replies:** 10\
**Last updated:** [December 11, 2023, 4:02pm UTC](https://discourse.julialang.org/t/double-pendulum-animation-with-julia/89142 "2023-12-11T16:02:12Z")

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Hi all, I saw this webpages: https://math24.net/double-pendulum.html https://www.myphysicslab.com/pendulum/double-pendulum-en.html and wonder how to create the double pendulum animation with its track in Julia? If p…

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## [Broadcasting getproperty over an empty vector of structs does return Any\[\] instead of a concrete type](https://discourse.julialang.org/t/broadcasting-getproperty-over-an-empty-vector-of-structs-does-return-any-instead-of-a-concrete-type/107439)

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**Author:** [@florian](https://discourse.julialang.org/u/florian)\
**Replies:** 2\
**Last updated:** [December 11, 2023, 3:58pm UTC](https://discourse.julialang.org/t/broadcasting-getproperty-over-an-empty-vector-of-structs-does-return-any-instead-of-a-concrete-type/107439 "2023-12-11T15:58:48Z")

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I’m not sure if this is a bug, or if I am missing something: struct X a::String end struct Y a::String b::Vector{String} end x = X\[\] y = Y\[\] Broadcasting getproperty(..., :a) over x and y does return Stri…

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## [Workaround for CompatHelper Bug](https://discourse.julialang.org/t/workaround-for-compathelper-bug/107449)

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**Author:** [@Nathan\_Boyer](https://discourse.julialang.org/u/Nathan_Boyer)\
**Replies:** 2\
**Last updated:** [December 11, 2023, 3:56pm UTC](https://discourse.julialang.org/t/workaround-for-compathelper-bug/107449 "2023-12-11T15:56:09Z")

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I keep getting this pull request from CompatHelper: This pull request changes the compat entry for the XLSX package from 0.10.1 to 0.10.1, 0.10. The current compat is listed as XLSX = "0.10.1" which seems correct acc…

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## [REPL open editor mode](https://discourse.julialang.org/t/repl-open-editor-mode/107446)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 1\
**Last updated:** [December 11, 2023, 3:27pm UTC](https://discourse.julialang.org/t/repl-open-editor-mode/107446 "2023-12-11T15:27:37Z")

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In the JuliaCon 2023 State of Julia talk the mode where the REPL can open your favourite $EDITOR was mentioned. I thought this was done using CTRL-E Did I misunderstand this?

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## [Tutorials/books on C++ Object Oriented methodology to Julia Multiple Dispatch](https://discourse.julialang.org/t/tutorials-books-on-c-object-oriented-methodology-to-julia-multiple-dispatch/107289)

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**Author:** [@PatrickChampion.NCHS](https://discourse.julialang.org/u/PatrickChampion.NCHS)\
**Replies:** 13\
**Last updated:** [December 11, 2023, 3:23pm UTC](https://discourse.julialang.org/t/tutorials-books-on-c-object-oriented-methodology-to-julia-multiple-dispatch/107289 "2023-12-11T15:23:03Z")

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Can someone give like the 5 best Tutorials, whitepapers, or books that clearly describe how to map classic C++ (or Java) object orientation (inheritance, virtual constructor/destructors, polymorphism, and templates) into…

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## [Julia Systems Biology community calls](https://discourse.julialang.org/t/julia-systems-biology-community-calls/107447)

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**Author:** [@isaacsas](https://discourse.julialang.org/u/isaacsas)\
**Replies:** 0\
**Last updated:** [December 11, 2023, 2:29pm UTC](https://discourse.julialang.org/t/julia-systems-biology-community-calls/107447 "2023-12-11T14:29:34Z")

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@paulflang has kindly organized a (virtual) Julia Systems Biology community call that will begin this week on Wednesday 12/13 at 6pm UTC. Please see the info below. The link for the call has been posted on the sciml-sys…

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## [Problem with ForwardDiff not letting me update variable "d"](https://discourse.julialang.org/t/problem-with-forwarddiff-not-letting-me-update-variable-d/107417)

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**Author:** [@bdas123](https://discourse.julialang.org/u/bdas123)\
**Replies:** 7\
**Last updated:** [December 11, 2023, 2:27pm UTC](https://discourse.julialang.org/t/problem-with-forwarddiff-not-letting-me-update-variable-d/107417 "2023-12-11T14:27:10Z")

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Here is a watered down version of code I am using a = zeros(2393) a = findall(x -\> x == 0, a) b = zeros(293) e = rand(2979) l = zeros(137,293) g = ones(137,293) h = rand(137,170) function dummy(e::T...) where {T}…

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## [Resources to Understand Distributed.jl](https://discourse.julialang.org/t/resources-to-understand-distributed-jl/107395)

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**Author:** [@bdas123](https://discourse.julialang.org/u/bdas123)\
**Replies:** 5\
**Last updated:** [December 11, 2023, 1:50pm UTC](https://discourse.julialang.org/t/resources-to-understand-distributed-jl/107395 "2023-12-11T13:50:05Z")

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Besides the Distributed.jl documentation, are there any other good resources to understand the theory/application of the library? I’d figure to ask here before I do a deep dive on the topic.

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## [Numerical differences depending on loading order](https://discourse.julialang.org/t/numerical-differences-depending-on-loading-order/107362)

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**Author:** [@philbit](https://discourse.julialang.org/u/philbit)\
**Replies:** 16\
**Last updated:** [December 11, 2023, 1:11pm UTC](https://discourse.julialang.org/t/numerical-differences-depending-on-loading-order/107362 "2023-12-11T13:11:49Z")

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We are doing large-scale numerical simulations and discovered a reproducibility issue with our numerical code, where the output was different depending on whether we were producing plots on the fly or not. After an “exci…

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## [Trouble Enabling Multithreading within Jupyter Notebook](https://discourse.julialang.org/t/trouble-enabling-multithreading-within-jupyter-notebook/107411)

<div class="topic-metadata">

**Author:** [@bdas123](https://discourse.julialang.org/u/bdas123)\
**Replies:** 5\
**Last updated:** [December 11, 2023, 1:10pm UTC](https://discourse.julialang.org/t/trouble-enabling-multithreading-within-jupyter-notebook/107411 "2023-12-11T13:10:48Z")

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When I execute the following command: using IJulia installkernel("Julia (4 threads)", env=Dict("JULIA\_NUM\_THREADS"=\>"4")) Threads.nthreads() I only get 1 thread. Is there a way to increase the number of threads within …

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## [Is it expected that a zero-one variable may have a non-integer value after an optimal solution is found?](https://discourse.julialang.org/t/is-it-expected-that-a-zero-one-variable-may-have-a-non-integer-value-after-an-optimal-solution-is-found/107430)

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**Author:** [@nsajko](https://discourse.julialang.org/u/nsajko)\
**Replies:** 5\
**Last updated:** [December 11, 2023, 12:37pm UTC](https://discourse.julialang.org/t/is-it-expected-that-a-zero-one-variable-may-have-a-non-integer-value-after-an-optimal-solution-is-found/107430 "2023-12-11T12:37:37Z")

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I formulate a mathematical optimization (MIQCP) problem with MathOptInterface.jl and solve it with Gurobi.jl. Certain variables in my problem are constrained (with MOI.add\_constrained\_variables(optimizer, \[MOI.ZeroOne() …

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## [How i can host my julia api for free](https://discourse.julialang.org/t/how-i-can-host-my-julia-api-for-free/107158)

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**Author:** [@Night\_Xcros](https://discourse.julialang.org/u/Night_Xcros)\
**Replies:** 7\
**Last updated:** [December 11, 2023, 12:29pm UTC](https://discourse.julialang.org/t/how-i-can-host-my-julia-api-for-free/107158 "2023-12-11T12:29:16Z")

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how i can host my julia api for free,is there any unoficioal trick for host it for free

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## [Memoizing a function using only a subset of arguments as an identifier](https://discourse.julialang.org/t/memoizing-a-function-using-only-a-subset-of-arguments-as-an-identifier/107426)

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**Author:** [@Aleksandr\_Mikheev](https://discourse.julialang.org/u/Aleksandr_Mikheev)\
**Replies:** 3\
**Last updated:** [December 11, 2023, 12:16pm UTC](https://discourse.julialang.org/t/memoizing-a-function-using-only-a-subset-of-arguments-as-an-identifier/107426 "2023-12-11T12:16:20Z")

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Suppose I have a function of two arguments. For instance, function foo(a::Float64,b::Float64) return a^2 - b end Is it possible to memoize it based on the first argument only? I understand how I can partially achiev…

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## [Multi-threading + curve\_fit no acceleration but increase the memory consumption on my server](https://discourse.julialang.org/t/multi-threading-curve-fit-no-acceleration-but-increase-the-memory-consumption-on-my-server/107429)

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**Author:** [@aTrotier](https://discourse.julialang.org/u/aTrotier)\
**Replies:** 0\
**Last updated:** [December 11, 2023, 11:40am UTC](https://discourse.julialang.org/t/multi-threading-curve-fit-no-acceleration-but-increase-the-memory-consumption-on-my-server/107429 "2023-12-11T11:40:11Z")

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Hi, I am working with 3D + temporal dimension (12812896\*50) MRI datasets that I want to fit using curve\_fit with the following model. The memory consumption is particularly important using multi-threading and does not …

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## [Troubleshooting an Unhandled error in Parallel Computation on a Slurm Cluster](https://discourse.julialang.org/t/troubleshooting-an-unhandled-error-in-parallel-computation-on-a-slurm-cluster/107427)

<div class="topic-metadata">

**Author:** [@shahmari](https://discourse.julialang.org/u/shahmari)\
**Replies:** 0\
**Last updated:** [December 11, 2023, 10:43am UTC](https://discourse.julialang.org/t/troubleshooting-an-unhandled-error-in-parallel-computation-on-a-slurm-cluster/107427 "2023-12-11T10:43:26Z")

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Hello Julia community! I’m encountering an issue with distributing some computation across threads of multiple nodes in a Slurm cluster. I’m using Distributed.jl, SlurmClusterManager.jl, and SharedArrays.jl to paralleli…

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## [Should we distribute multiple official system images for Julia 1.11?](https://discourse.julialang.org/t/should-we-distribute-multiple-official-system-images-for-julia-1-11/107353)

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**Author:** [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Replies:** 50\
**Last updated:** [December 11, 2023, 9:45am UTC](https://discourse.julialang.org/t/should-we-distribute-multiple-official-system-images-for-julia-1-11/107353 "2023-12-11T09:45:02Z")

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In Julia 1.11, REPL.jl and Pkg.jl are now independent packages and not standard in the system image. This will help slim down the system image and make Julia’s packaging more modular. REPL.jl and Pkg.jl will be able to u…

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## [CondaPkg - acitvate environment](https://discourse.julialang.org/t/condapkg-acitvate-environment/107341)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 6\
**Last updated:** [December 11, 2023, 9:31am UTC](https://discourse.julialang.org/t/condapkg-acitvate-environment/107341 "2023-12-11T09:31:30Z")

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I am using CondaPkg and installed two Python packages. After installation I get the message: To activate this environment, use: micromamba activate /home/ufechner/repos/Tethers.jl/.CondaPkg/env But that does not w…

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## [How to know which ContinuedFractions package to use?](https://discourse.julialang.org/t/how-to-know-which-continuedfractions-package-to-use/107381)

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**Author:** [@chandra](https://discourse.julialang.org/u/chandra)\
**Replies:** 2\
**Last updated:** [December 11, 2023, 8:31am UTC](https://discourse.julialang.org/t/how-to-know-which-continuedfractions-package-to-use/107381 "2023-12-11T08:31:44Z")

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I am interested in the ContinuedFractions package in Julia. I found two repositories: ContinuedFractions.jl-One and ContinuedFractions.jl-Two How do I find out which to use? If necessary, how do I uninstall the wro…

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## [Problem escaping 2nd dollar sign in plot title](https://discourse.julialang.org/t/problem-escaping-2nd-dollar-sign-in-plot-title/107388)

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**Author:** [@adannenberg](https://discourse.julialang.org/u/adannenberg)\
**Replies:** 4\
**Last updated:** [December 11, 2023, 6:23am UTC](https://discourse.julialang.org/t/problem-escaping-2nd-dollar-sign-in-plot-title/107388 "2023-12-11T06:23:25Z")

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Suppose I want a plot with the title “if you give me $2 then i will give you $1” If i construct str = "if you give me \\$2 then i will give you \\$1" then println(str) returns if you give me $2 then i will give you $…

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## [Gurobi AddGenConstrPoly() in JuMP](https://discourse.julialang.org/t/gurobi-addgenconstrpoly-in-jump/107123)

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**Author:** [@manoj.centura](https://discourse.julialang.org/u/manoj.centura)\
**Replies:** 7\
**Last updated:** [December 11, 2023, 5:17am UTC](https://discourse.julialang.org/t/gurobi-addgenconstrpoly-in-jump/107123 "2023-12-11T05:17:23Z")

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Hi All, Can we code GRBModel.AddGenConstrPoly() constraint available in gurobi directly in JuMP. The MINLP is solved using Juniper. we want to try Gurobi for this.

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## [Error with setting TZ=UTC when running touch in Julia](https://discourse.julialang.org/t/error-with-setting-tz-utc-when-running-touch-in-julia/107315)

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**Author:** [@KeepLearning](https://discourse.julialang.org/u/KeepLearning)\
**Replies:** 2\
**Last updated:** [December 11, 2023, 2:32am UTC](https://discourse.julialang.org/t/error-with-setting-tz-utc-when-running-touch-in-julia/107315 "2023-12-11T02:32:47Z")

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Hi, I wanted to run the unix command in Julia as follows: run(\`TZ=UTC touch -t "YYMMDDhhmm" filename\`) but got an IOError, assuming that I am in a different time zone from UTC and wanted to set the timestamp of a file…

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## [All positive eigen values but false in isposdef?](https://discourse.julialang.org/t/all-positive-eigen-values-but-false-in-isposdef/107393)

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**Author:** [@Wooheon](https://discourse.julialang.org/u/Wooheon)\
**Replies:** 2\
**Last updated:** [December 11, 2023, 1:25am UTC](https://discourse.julialang.org/t/all-positive-eigen-values-but-false-in-isposdef/107393 "2023-12-11T01:25:28Z")

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Hello, I was curious about my Julia code spitting out negative variance for some variations in sandwich form vcov matrices (in Fixed Effects, clustering etc.). Let’s say my matrix of control variables, X. I found out t…

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## [Difference between JuliaGPU and Distributed.jl](https://discourse.julialang.org/t/difference-between-juliagpu-and-distributed-jl/107394)

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**Author:** [@bdas123](https://discourse.julialang.org/u/bdas123)\
**Replies:** 2\
**Last updated:** [December 11, 2023, 1:07am UTC](https://discourse.julialang.org/t/difference-between-juliagpu-and-distributed-jl/107394 "2023-12-11T01:07:01Z")

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Hello! This is more of a conceptual question. It seems like Distributed.jl and JuliaGPU.jl both take advantage of parallel operations. I guess what’s the difference? Why use JuilaGPU when Distributed gets the same job …

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## [Understanding the behaviour of Butterworth filter in DSP](https://discourse.julialang.org/t/understanding-the-behaviour-of-butterworth-filter-in-dsp/107396)

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**Author:** [@PeX](https://discourse.julialang.org/u/PeX)\
**Replies:** 3\
**Last updated:** [December 11, 2023, 12:57am UTC](https://discourse.julialang.org/t/understanding-the-behaviour-of-butterworth-filter-in-dsp/107396 "2023-12-11T00:57:52Z")

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Hi all, I’m using a highpass filter to isolate the oscillations from the trend in my signal. The filter I use for my time series signal is: response = Highpass((𝑓/1); fs) design = Butterworth(2) filtered = filt(digital…

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## [‘show’ function for user-defined struct](https://discourse.julialang.org/t/show-function-for-user-defined-struct/107391)

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**Author:** [@jiang\_ming\_zhang](https://discourse.julialang.org/u/jiang_ming_zhang)\
**Replies:** 1\
**Last updated:** [December 11, 2023, 12:14am UTC](https://discourse.julialang.org/t/show-function-for-user-defined-struct/107391 "2023-12-11T00:14:56Z")

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julia\> struct my age :: Int weight :: Float64 end julia\> function Base.show(io::IO, h::my) print(io,"my struct") end Here I defined a struct and a new method for the function ‘show’. …

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## [Minimisation with equality constraints](https://discourse.julialang.org/t/minimisation-with-equality-constraints/107358)

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**Author:** [@eveningsilverfox](https://discourse.julialang.org/u/eveningsilverfox)\
**Replies:** 5\
**Last updated:** [December 10, 2023, 9:13pm UTC](https://discourse.julialang.org/t/minimisation-with-equality-constraints/107358 "2023-12-10T21:13:06Z")

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I am trying a constrained minimisation with equality constraints. using LinearAlgebra using Optimization, OptimizationMOI, AmplNLWriter, Ipopt\_jll function objectivehelp(N) car = rand(N) .+ 1; sar = rand(N); r…

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## [Speed comparison on reading a gzip file](https://discourse.julialang.org/t/speed-comparison-on-reading-a-gzip-file/56471)

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**Author:** [@calvin](https://discourse.julialang.org/u/calvin)\
**Replies:** 8\
**Last updated:** [December 10, 2023, 8:45pm UTC](https://discourse.julialang.org/t/speed-comparison-on-reading-a-gzip-file/56471 "2023-12-10T20:45:35Z")

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Hi there, perl using shell piping took ~32 seconds. python using shell piping took ~ 36 seconds. julia using shell piping took ~ 70 seconds. julia using GzipDecompressorStream from CodecZlib, which has been recommend…

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