# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=88

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

**Page:** 89

---

## [Pluto and Bandits](https://discourse.julialang.org/t/pluto-and-bandits/125648)

<div class="topic-metadata">

**Author:** [@Jose\_Ghislain\_Quenum](https://discourse.julialang.org/u/Jose_Ghislain_Quenum)\
**Replies:** 2\
**Last updated:** [February 8, 2025, 9:25am UTC](https://discourse.julialang.org/t/pluto-and-bandits/125648 "2025-02-08T09:25:33Z")

</div>

Good day all, I have two quick questions. 1 - Is GitHub - rawls238/Bandits.jl: Implementation of multi-armed bandits in Julia the only implementation for the multi-armed bandits problem in Julia? 2- I am getting an error…

---

## [Using BoundaryValueDiffEqFIRK: what is the format for solution derivative in bc! function?](https://discourse.julialang.org/t/using-boundaryvaluediffeqfirk-what-is-the-format-for-solution-derivative-in-bc-function/125600)

<div class="topic-metadata">

**Author:** [@P0p5](https://discourse.julialang.org/u/P0p5)\
**Replies:** 5\
**Last updated:** [February 8, 2025, 8:09am UTC](https://discourse.julialang.org/t/using-boundaryvaluediffeqfirk-what-is-the-format-for-solution-derivative-in-bc-function/125600 "2025-02-08T08:09:33Z")

</div>

I’m trying to use BVProblem with solver RadauIIa5. In the boundary condition function called by the solver, I need to refer to the first derivative of the solution. I can’t find an acceptable form for this derivative …

---

## [Flux lines plot](https://discourse.julialang.org/t/flux-lines-plot/125619)

<div class="topic-metadata">

**Author:** [@lmiq](https://discourse.julialang.org/u/lmiq)\
**Replies:** 13\
**Last updated:** [February 8, 2025, 1:17am UTC](https://discourse.julialang.org/t/flux-lines-plot/125619 "2025-02-08T01:17:36Z")

</div>

We would like to produce an image similar to this one: except that what we have has nothing to do with climate. We have the density of a property on the surface of a sphere as a function of time. What are the tools …

---

## [How to make a locally defined function type-stable?](https://discourse.julialang.org/t/how-to-make-a-locally-defined-function-type-stable/125639)

<div class="topic-metadata">

**Author:** [@rkube](https://discourse.julialang.org/u/rkube)\
**Replies:** 7\
**Last updated:** [February 7, 2025, 7:26pm UTC](https://discourse.julialang.org/t/how-to-make-a-locally-defined-function-type-stable/125639 "2025-02-07T19:26:53Z")

</div>

Hi, I’m wondering how and where I can add type annotations to make some code type-stable. I’m working with a structure: struct sensor{T} location normal α parameters id end The fields and locati…

---

## [How to make splat, map and tuples be efficient](https://discourse.julialang.org/t/how-to-make-splat-map-and-tuples-be-efficient/125653)

<div class="topic-metadata">

**Author:** [@garazha-ilya](https://discourse.julialang.org/u/garazha-ilya)\
**Replies:** 3\
**Last updated:** [February 7, 2025, 7:08pm UTC](https://discourse.julialang.org/t/how-to-make-splat-map-and-tuples-be-efficient/125653 "2025-02-07T19:08:29Z")

</div>

Generally I want to make f(g("a"), g("c"), g("k")) with f(map(g, \["a","c","k"\])...) be efficient and don’t generate allocations. And I started experimenting, by creating 3 functions: function foo\_tuple(a,b,c) …

---

## [Forward all function calls on ::MyType to another wrapped field](https://discourse.julialang.org/t/forward-all-function-calls-on-mytype-to-another-wrapped-field/105750)

<div class="topic-metadata">

**Author:** [@pablosanjose](https://discourse.julialang.org/u/pablosanjose)\
**Replies:** 20\
**Last updated:** [February 7, 2025, 6:51pm UTC](https://discourse.julialang.org/t/forward-all-function-calls-on-mytype-to-another-wrapped-field/105750 "2025-02-07T18:51:50Z")

</div>

In Julia we cannot inherit from a concrete type. The advice often given to overcome this limitation is to use type composition, i.e. instead of making a type B a subtype of a concrete type A, wrap an instance of A in B,…

---

## [Documenter to github pages: build successful and pushed but page does not exist](https://discourse.julialang.org/t/documenter-to-github-pages-build-successful-and-pushed-but-page-does-not-exist/125183)

<div class="topic-metadata">

**Author:** [@amaresh-sahu](https://discourse.julialang.org/u/amaresh-sahu)\
**Replies:** 1\
**Last updated:** [February 7, 2025, 4:13pm UTC](https://discourse.julialang.org/t/documenter-to-github-pages-build-successful-and-pushed-but-page-does-not-exist/125183 "2025-02-07T16:13:24Z")

</div>

I am trying to push documentation for a package I wrote (currently not registered) to github pages. So far I: have the source code in a repo: GitHub - sahu-lab/MembraneAleFem.jl: source code for arbitrary Lagrangian--E…

---

## [Difference between Tuple and NTuple](https://discourse.julialang.org/t/difference-between-tuple-and-ntuple/107357)

<div class="topic-metadata">

**Author:** [@jiang\_ming\_zhang](https://discourse.julialang.org/u/jiang_ming_zhang)\
**Replies:** 2\
**Last updated:** [February 7, 2025, 2:14pm UTC](https://discourse.julialang.org/t/difference-between-tuple-and-ntuple/107357 "2025-02-07T14:14:21Z")

</div>

Is ‘NTuple’ a more specific ‘Tuple’? It seems that in a Tuple, the elements can have different types, but in an NTuple, the elements must have the same type?

---

## [Error "cannot enable executable stack" when starting Julia (solved)](https://discourse.julialang.org/t/error-cannot-enable-executable-stack-when-starting-julia-solved/125655)

<div class="topic-metadata">

**Author:** [@marllos](https://discourse.julialang.org/u/marllos)\
**Replies:** 1\
**Last updated:** [February 7, 2025, 12:32pm UTC](https://discourse.julialang.org/t/error-cannot-enable-executable-stack-when-starting-julia-solved/125655 "2025-02-07T12:32:17Z")

</div>

Recently, I encountered an unexpected issue when trying to run Julia on my Arch Linux. Everything had been working fine until suddenly Julia started failing with the following error: ERROR: Unable to load dependent libr…

---

## [Arc length for a spline](https://discourse.julialang.org/t/arc-length-for-a-spline/36161)

<div class="topic-metadata">

**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 27\
**Last updated:** [February 7, 2025, 8:04am UTC](https://discourse.julialang.org/t/arc-length-for-a-spline/36161 "2025-02-07T08:04:11Z")

</div>

Given some spline (e.g. Dierckx.jl, Interpolations.jl), is there a good way to get its arc length? Right now I’m using this: using LinearAlgebra, Dierckx t = range(0, stop = π, length = 100) x = cos.(t) y = sin.(t) spl…

---

## [Sparse matrix of vectors](https://discourse.julialang.org/t/sparse-matrix-of-vectors/125636)

<div class="topic-metadata">

**Author:** [@pulk\_jain](https://discourse.julialang.org/u/pulk_jain)\
**Replies:** 5\
**Last updated:** [February 6, 2025, 11:59pm UTC](https://discourse.julialang.org/t/sparse-matrix-of-vectors/125636 "2025-02-06T23:59:56Z")

</div>

Hi, I wanted to store some information as a sparse matrix of vectors (or a tuple) to save on memory requirements. I am simulating a system of N(~50) particles in a box. If two particles contact then there are interactio…

---

## [Symbolics.jl - failing to simplify N-over-1 rational literals within expression](https://discourse.julialang.org/t/symbolics-jl-failing-to-simplify-n-over-1-rational-literals-within-expression/125446)

<div class="topic-metadata">

**Author:** [@jl\_enthusiast](https://discourse.julialang.org/u/jl_enthusiast)\
**Replies:** 4\
**Last updated:** [February 6, 2025, 9:28pm UTC](https://discourse.julialang.org/t/symbolics-jl-failing-to-simplify-n-over-1-rational-literals-within-expression/125446 "2025-02-06T21:28:54Z")

</div>

Hi, I am currently trying to write some custom simplification rules throughout different stages of a symbolic manipulation process. One thing I noticed is that no matter how I try, I can’t come up with a rule that canc…

---

## [Pretty print matrix a la display](https://discourse.julialang.org/t/pretty-print-matrix-a-la-display/125590)

<div class="topic-metadata">

**Author:** [@Markos\_Kapes](https://discourse.julialang.org/u/Markos_Kapes)\
**Replies:** 6\
**Last updated:** [February 6, 2025, 7:01pm UTC](https://discourse.julialang.org/t/pretty-print-matrix-a-la-display/125590 "2025-02-06T19:01:20Z")

</div>

if I have a matrix a = \[1 2; 3 4\] is there a way to get the string that display() pretty prints like so? 2×2 Matrix{Int64}: 1 2 3 4 I’m wondering because I want to be able to embed a depiction of the matrix in Plut…

---

## [Using BoundaryValueDiffEqFIRK: How many boundary condition residual elements allowed?](https://discourse.julialang.org/t/using-boundaryvaluediffeqfirk-how-many-boundary-condition-residual-elements-allowed/125602)

<div class="topic-metadata">

**Author:** [@P0p5](https://discourse.julialang.org/u/P0p5)\
**Replies:** 5\
**Last updated:** [February 6, 2025, 6:51pm UTC](https://discourse.julialang.org/t/using-boundaryvaluediffeqfirk-how-many-boundary-condition-residual-elements-allowed/125602 "2025-02-06T18:51:37Z")

</div>

Again, I’m trying to use BVProblem with solver RadauIIa5. In the boundary condition function called by the solver, what is the maximum length of the residual vector, which is the first argument of this function? I am …

---

## [Markdown supported code-block languages](https://discourse.julialang.org/t/markdown-supported-code-block-languages/69293)

<div class="topic-metadata">

**Author:** [@disberd](https://discourse.julialang.org/u/disberd)\
**Replies:** 1\
**Last updated:** [February 6, 2025, 5:22pm UTC](https://discourse.julialang.org/t/markdown-supported-code-block-languages/69293 "2025-02-06T17:22:14Z")

</div>

What are the language supported for synthax highlighting in markdown? Like this in a Pluto notebook for example: I have seen javascript and julia being used but didn’t find any reference saying which languages are s…

---

## [Should one use Julia to create libraries?](https://discourse.julialang.org/t/should-one-use-julia-to-create-libraries/125622)

<div class="topic-metadata">

**Author:** [@cocoa1231](https://discourse.julialang.org/u/cocoa1231)\
**Replies:** 4\
**Last updated:** [February 6, 2025, 4:01pm UTC](https://discourse.julialang.org/t/should-one-use-julia-to-create-libraries/125622 "2025-02-06T16:01:53Z")

</div>

I was browsing the thread on why LoopVectorization.jl is deprecated, and I came across LoopModels, which is a successor to LoopVectorization.jl, and this made me wonder if one should be writing general purpose libraries …

---

## [Reducing RAM usage when solving large set of differential equations](https://discourse.julialang.org/t/reducing-ram-usage-when-solving-large-set-of-differential-equations/125610)

<div class="topic-metadata">

**Author:** [@diffeqslvr](https://discourse.julialang.org/u/diffeqslvr)\
**Replies:** 5\
**Last updated:** [February 6, 2025, 3:27pm UTC](https://discourse.julialang.org/t/reducing-ram-usage-when-solving-large-set-of-differential-equations/125610 "2025-02-06T15:27:57Z")

</div>

I am solving a large system of differential equations (O(500 000) equations). Unsurprisingly, I run into RAM issues. I already tried to only save a subset of O(13 000) variables using a SavingCallback saved\_values = Sav…

---

## [Circular dependencies in Julia 1.10.8](https://discourse.julialang.org/t/circular-dependencies-in-julia-1-10-8/125587)

<div class="topic-metadata">

**Author:** [@prittjam](https://discourse.julialang.org/u/prittjam)\
**Replies:** 3\
**Last updated:** [February 6, 2025, 2:33pm UTC](https://discourse.julialang.org/t/circular-dependencies-in-julia-1-10-8/125587 "2025-02-06T14:33:40Z")

</div>

With the following using BandedMatrices, Colors, Distributions, GLMakie, Infiltrator, Intervals, Images, JuMP, LinearAlgebra, Parameters, OSQP, Random, SparseArrays, StaticArrays, StatsBase, StructArrays…

---

## [Declaring (non-parametric) type with unspecified types inside](https://discourse.julialang.org/t/declaring-non-parametric-type-with-unspecified-types-inside/125620)

<div class="topic-metadata">

**Author:** [@azoviktor](https://discourse.julialang.org/u/azoviktor)\
**Replies:** 1\
**Last updated:** [February 6, 2025, 1:04pm UTC](https://discourse.julialang.org/t/declaring-non-parametric-type-with-unspecified-types-inside/125620 "2025-02-06T13:04:36Z")

</div>

If I declare a type as struct Test x::T where T end is it identical to declaring it as struct Test x::Any end ?

---

## [How to quantitatively analyze the impact of memory bandwidth on multithreading](https://discourse.julialang.org/t/how-to-quantitatively-analyze-the-impact-of-memory-bandwidth-on-multithreading/125059)

<div class="topic-metadata">

**Author:** [@quantumdreamer](https://discourse.julialang.org/u/quantumdreamer)\
**Replies:** 10\
**Last updated:** [February 6, 2025, 3:20am UTC](https://discourse.julialang.org/t/how-to-quantitatively-analyze-the-impact-of-memory-bandwidth-on-multithreading/125059 "2025-02-06T03:20:15Z")

</div>

When I increased the number of threads in my Julia project, I noticed that the performance of the project did not scale linearly with the number of threads. Currently, the multi-threaded performance is twice that of the …

---

## [How To Quickly Iterate over a Collection of Dictionaries?](https://discourse.julialang.org/t/how-to-quickly-iterate-over-a-collection-of-dictionaries/125588)

<div class="topic-metadata">

**Author:** [@TheCedarPrince](https://discourse.julialang.org/u/TheCedarPrince)\
**Replies:** 2\
**Last updated:** [February 5, 2025, 9:35pm UTC](https://discourse.julialang.org/t/how-to-quickly-iterate-over-a-collection-of-dictionaries/125588 "2025-02-05T21:35:51Z")

</div>

Hi folks! :wave: I have a rather large JSON file. The good news is that the JSON is not heavily nested (only 2 levels deep). What is the most efficient way to filter relevant parts of a JSON structure I need based on a …

---

## [Implementation of Octave functions in Julia](https://discourse.julialang.org/t/implementation-of-octave-functions-in-julia/39631)

<div class="topic-metadata">

**Author:** [@alejandrovpm](https://discourse.julialang.org/u/alejandrovpm)\
**Replies:** 16\
**Last updated:** [February 5, 2025, 5:27pm UTC](https://discourse.julialang.org/t/implementation-of-octave-functions-in-julia/39631 "2025-02-05T17:27:15Z")

</div>

Hello everyone, I wonder if there is a way to implement Matlab functions via Octave in Julia. I know there exists Matlab.jl but for using it you need to install a Matlab version in your computer. I ask this question be…

---

## [Cannot install Concorde.jl on Mac OS M3](https://discourse.julialang.org/t/cannot-install-concorde-jl-on-mac-os-m3/125505)

<div class="topic-metadata">

**Author:** [@mposs](https://discourse.julialang.org/u/mposs)\
**Replies:** 3\
**Last updated:** [February 5, 2025, 5:03pm UTC](https://discourse.julialang.org/t/cannot-install-concorde-jl-on-mac-os-m3/125505 "2025-02-05T17:03:40Z")

</div>

Hi Would someone happen to know how to solve the problem when installing Concorde.jl: (@v1.11) pkg\> add Concorde Resolving package versions... No Changes to \`~/.julia/environments/v1.11/Project.toml\` No Changes …

---

## [How can I check if step!() was successful?](https://discourse.julialang.org/t/how-can-i-check-if-step-was-successful/125581)

<div class="topic-metadata">

**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 7\
**Last updated:** [February 5, 2025, 3:36pm UTC](https://discourse.julialang.org/t/how-can-i-check-if-step-was-successful/125581 "2025-02-05T15:36:32Z")

</div>

In my code I have the line: OrdinaryDiffEqCore.step!(integrator, dt, true) Normally it works, but sometimes it doesn’t. How can I check if an error occurred, and if yes which one? The integrator was created using: s…

---

## [Keep array elements that are NOT in a list of indexes](https://discourse.julialang.org/t/keep-array-elements-that-are-not-in-a-list-of-indexes/125555)

<div class="topic-metadata">

**Author:** [@JM\_Beckers](https://discourse.julialang.org/u/JM_Beckers)\
**Replies:** 8\
**Last updated:** [February 5, 2025, 12:40pm UTC](https://discourse.julialang.org/t/keep-array-elements-that-are-not-in-a-list-of-indexes/125555 "2025-02-05T12:40:55Z")

</div>

Suppose I have a list of indexes mylist, is there an equivalent of setdiff(myarray, myarray\[mylist\]) but using directly the fact that I know which elements are to the eliminated (through mylist) in order to be more ef…

---

## [Distributed fails to create command on ssh connection to remote worker](https://discourse.julialang.org/t/distributed-fails-to-create-command-on-ssh-connection-to-remote-worker/114704)

<div class="topic-metadata">

**Author:** [@Teodor\_Tchalakov](https://discourse.julialang.org/u/Teodor_Tchalakov)\
**Replies:** 1\
**Last updated:** [February 5, 2025, 10:08am UTC](https://discourse.julialang.org/t/distributed-fails-to-create-command-on-ssh-connection-to-remote-worker/114704 "2025-02-05T10:08:40Z")

</div>

When adding remote workers through an ssh connection using Distributed.jl, the SSH Manager is able to connect but for some reason a command over ssh gets improperly formatted and setting up the remote workers fails. The …

---

## [Sublim-julia](https://discourse.julialang.org/t/sublim-julia/125564)

<div class="topic-metadata">

**Author:** [@Science\_Magus](https://discourse.julialang.org/u/Science_Magus)\
**Replies:** 2\
**Last updated:** [February 5, 2025, 8:49am UTC](https://discourse.julialang.org/t/sublim-julia/125564 "2025-02-05T08:49:45Z")

</div>

Hello every one I need the path way of julia languag ein ubuntu 24, for running the julia code. Thank you very much

---

## [Exception: EXCEPTION\_ACCESS\_VIOLATION](https://discourse.julialang.org/t/exception-exception-access-violation/125545)

<div class="topic-metadata">

**Author:** [@hssn15](https://discourse.julialang.org/u/hssn15)\
**Replies:** 3\
**Last updated:** [February 4, 2025, 11:43pm UTC](https://discourse.julialang.org/t/exception-exception-access-violation/125545 "2025-02-04T23:43:25Z")

</div>

Hi, I am really struggling with this problem. Sometimes it happens some times it doesn’t. Could anyone give some advice ? Please submit a bug report with steps to reproduce this fault, and any error messages that follow…

---

## [Elegant way of exclusive indexing](https://discourse.julialang.org/t/elegant-way-of-exclusive-indexing/76894)

<div class="topic-metadata">

**Author:** [@TheLateKronos](https://discourse.julialang.org/u/TheLateKronos)\
**Replies:** 41\
**Last updated:** [February 26, 2022, 4:34pm UTC](https://discourse.julialang.org/t/elegant-way-of-exclusive-indexing/76894 "2022-02-26T16:34:17Z")

</div>

In R, you can index all elements except for the second, by negative indexing: myvector\[-2\]. This is especially usefull if you want to make two complete subsets of a vector: set1 = myvector\[inds\] set2 = myvector\[-inds\] W…

---

## [Compare dataframes regardless of column order](https://discourse.julialang.org/t/compare-dataframes-regardless-of-column-order/125491)

<div class="topic-metadata">

**Author:** [@fran94](https://discourse.julialang.org/u/fran94)\
**Replies:** 8\
**Last updated:** [February 4, 2025, 2:42pm UTC](https://discourse.julialang.org/t/compare-dataframes-regardless-of-column-order/125491 "2025-02-04T14:42:17Z")

</div>

Hi! I’m probably doing something wrong but I cannot seem to find an easy solution to this. Imagine I have a dataframe (e.g. the Palmer penguins data) and I convert it from wide to tidy format: using PalmerPenguins, Dat…

[Previous page](https://discourse.julialang.org/c/usage/6.md?page=87)

[Next page](https://discourse.julialang.org/c/usage/6.md?page=89)