# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=332

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**Page:** 333

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## [Unable to install IJulia package](https://discourse.julialang.org/t/unable-to-install-ijulia-package/94163)

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**Author:** [@snowzone5](https://discourse.julialang.org/u/snowzone5)\
**Replies:** 14\
**Last updated:** [February 6, 2023, 10:01pm UTC](https://discourse.julialang.org/t/unable-to-install-ijulia-package/94163 "2023-02-06T22:01:25Z")

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Apologies if this is the wrong area. I was directed here from the IJulia Github page (I got it wrong there also) I am unable install IJulia on Windows 10. Please let me know if I should continue or this topic should m…

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## [Symbolics substitute and simplify in a polynomial](https://discourse.julialang.org/t/symbolics-substitute-and-simplify-in-a-polynomial/94160)

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**Author:** [@Jake](https://discourse.julialang.org/u/Jake)\
**Replies:** 4\
**Last updated:** [February 6, 2023, 8:59pm UTC](https://discourse.julialang.org/t/symbolics-substitute-and-simplify-in-a-polynomial/94160 "2023-02-06T20:59:39Z")

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This is my first time using Symbolics. I have a polynomial that I want to substitute a variable and then simplify the result as shown. julia\> dcs\_P1 = 229.50752 - 321.64369 \* r - 121.01008 \* r^2 + 53.15226 \* r^3 229.50…

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## [Default project activation via Pkg.jl or DrWatson.jl](https://discourse.julialang.org/t/default-project-activation-via-pkg-jl-or-drwatson-jl/94157)

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**Author:** [@mocalvao](https://discourse.julialang.org/u/mocalvao)\
**Replies:** 8\
**Last updated:** [February 6, 2023, 8:43pm UTC](https://discourse.julialang.org/t/default-project-activation-via-pkg-jl-or-drwatson-jl/94157 "2023-02-06T20:43:02Z")

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Right now my, I have several directories, which have Project.toml files because of 2 situations: (1) I have cloned them from Github repos, or (2) I have created them myself as DrWatson.jl “scientific” projects. In ord…

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## [CartesianIndices performance: 3D faster than 2D?](https://discourse.julialang.org/t/cartesianindices-performance-3d-faster-than-2d/94110)

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**Author:** [@lntricate](https://discourse.julialang.org/u/lntricate)\
**Replies:** 2\
**Last updated:** [February 6, 2023, 8:16pm UTC](https://discourse.julialang.org/t/cartesianindices-performance-3d-faster-than-2d/94110 "2023-02-06T20:16:52Z")

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I have encountered a strange occurence when testing the performance of CartesianIndices: using BenchmarkTools function test(t::Tuple) for \_ ∈ CartesianIndices(t) end end @btime test((100,)) # 3.094 ns @btime test(…

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## [Does anybody anywhere care about NaN payloads?](https://discourse.julialang.org/t/does-anybody-anywhere-care-about-nan-payloads/94152)

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**Author:** [@Lilith](https://discourse.julialang.org/u/Lilith)\
**Replies:** 2\
**Last updated:** [February 6, 2023, 7:21pm UTC](https://discourse.julialang.org/t/does-anybody-anywhere-care-about-nan-payloads/94152 "2023-02-06T19:21:05Z")

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There are a bunch of different NaN values. NaN and anotherNaN = reinterpret(Float64, reinterpret(UInt64, NaN) + 1) and NaN are two examples. There is a proposal to explicitly disclaim any garuntees about which NaN you re…

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## [Google Colab compatibility broken](https://discourse.julialang.org/t/google-colab-compatibility-broken/93004)

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**Author:** [@MilesCranmer](https://discourse.julialang.org/u/MilesCranmer)\
**Replies:** 18\
**Last updated:** [February 6, 2023, 7:04pm UTC](https://discourse.julialang.org/t/google-colab-compatibility-broken/93004 "2023-02-06T19:04:45Z")

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Edit \[Jan 30, 2023\] Looks like all versions of Julia now break :frowning\_face: Main GitHub Issues: Broken inside Google Colab · Issue #48461 · JuliaLang/julia · GitHub Colab update breaks compatibility with JuliaLang …

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## [Confusing dispatch problem](https://discourse.julialang.org/t/confusing-dispatch-problem/93760)

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**Author:** [@Euhan](https://discourse.julialang.org/u/Euhan)\
**Replies:** 9\
**Last updated:** [February 6, 2023, 6:01pm UTC](https://discourse.julialang.org/t/confusing-dispatch-problem/93760 "2023-02-06T18:01:37Z")

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I get an unexpected MethodError when running a piece of code. The relevant bit of the error output is: ERROR: LoadError: MethodError: no method matching make\_my\_model(::Int64, ::Int64, ::Int64; no\_inchannels=3) Closest …

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## [Using SymPy.jl with two variables](https://discourse.julialang.org/t/using-sympy-jl-with-two-variables/94148)

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**Author:** [@Firstname\_Lastname](https://discourse.julialang.org/u/Firstname_Lastname)\
**Replies:** 1\
**Last updated:** [February 6, 2023, 4:45pm UTC](https://discourse.julialang.org/t/using-sympy-jl-with-two-variables/94148 "2023-02-06T16:45:09Z")

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I ran the following code using SymPy @syms x y f(x,y) = cos(x - y) df(x,y) = sympy.diff(f(x,y),x) df(0,pi/2) # it is supposed to be 1, but an error occurs Please help me to resolve this problem. Thank you.

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## [Converting \`\`\`ComplexF64\`\`\` array to \`\`\`Float64\`\`\` array in-place?](https://discourse.julialang.org/t/converting-complexf64-array-to-float64-array-in-place/94007)

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**Author:** [@bremez](https://discourse.julialang.org/u/bremez)\
**Replies:** 5\
**Last updated:** [February 6, 2023, 4:17pm UTC](https://discourse.julialang.org/t/converting-complexf64-array-to-float64-array-in-place/94007 "2023-02-06T16:17:04Z")

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I have a calculation that manipulates and produces a ComplexF64 array (whose dimension varies by usage in different places in my codebase). I know the final result must be an array of real numbers, or suppose I only care…

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## [Sum of an empty array](https://discourse.julialang.org/t/sum-of-an-empty-array/94130)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 5\
**Last updated:** [February 6, 2023, 1:27pm UTC](https://discourse.julialang.org/t/sum-of-an-empty-array/94130 "2023-02-06T13:27:54Z")

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Hello, I need to calculate the sum of the values in the column of a DataFrame. But it can also be empty. How can I do that? sum(\[\]) gives an long stack trace…

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## [Killing long-running thread starting in a web server](https://discourse.julialang.org/t/killing-long-running-thread-starting-in-a-web-server/94128)

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**Author:** [@cjproud](https://discourse.julialang.org/u/cjproud)\
**Replies:** 1\
**Last updated:** [February 6, 2023, 9:54am UTC](https://discourse.julialang.org/t/killing-long-running-thread-starting-in-a-web-server/94128 "2023-02-06T09:54:27Z")

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I’m trying to use Oxygen.jl as an API for a long running ccall. I’m trying to create a toy example where, after 30 seconds, the solver task called by call\_solver() on a new thread is passed InterruptException and stops. …

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## [Specifying size of vector in a struct](https://discourse.julialang.org/t/specifying-size-of-vector-in-a-struct/94125)

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**Author:** [@udax](https://discourse.julialang.org/u/udax)\
**Replies:** 2\
**Last updated:** [February 6, 2023, 9:06am UTC](https://discourse.julialang.org/t/specifying-size-of-vector-in-a-struct/94125 "2023-02-06T09:06:50Z")

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I have a struct like so: struct rpoint pn::Int64 #patch number xyz::Vector{Float64} #coordinates end Note: the xyz field will always be populated with a vector of size 3. I have two questions: Is it true th…

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## [Calling max() atomically on a compound type](https://discourse.julialang.org/t/calling-max-atomically-on-a-compound-type/94028)

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**Author:** [@torrance](https://discourse.julialang.org/u/torrance)\
**Replies:** 8\
**Last updated:** [February 6, 2023, 3:57am UTC](https://discourse.julialang.org/t/calling-max-atomically-on-a-compound-type/94028 "2023-02-06T03:57:06Z")

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I’ve attempted to understand the Julia docs on the newish @atomic stuff multiple times and yet I’m still struggling to fully understand. The docs are actually quite sparse on the topic, and what’s worse is that they poin…

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## [Add .exe in PATH - Julia](https://discourse.julialang.org/t/add-exe-in-path-julia/93954)

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**Author:** [@Students](https://discourse.julialang.org/u/Students)\
**Replies:** 4\
**Last updated:** [February 6, 2023, 3:28am UTC](https://discourse.julialang.org/t/add-exe-in-path-julia/93954 "2023-02-06T03:28:36Z")

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Hi everyone, I am trying to run the “UnderwaterAcoustics” package in Julia. In the installation manual they have provided the following statement: Bellhop will only be available if you have a working copy of bellhop.ex…

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## [Type Stability Help](https://discourse.julialang.org/t/type-stability-help/94114)

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**Author:** [@fft](https://discourse.julialang.org/u/fft)\
**Replies:** 5\
**Last updated:** [February 6, 2023, 3:18am UTC](https://discourse.julialang.org/t/type-stability-help/94114 "2023-02-06T03:18:44Z")

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I am following along with Make Your Own Neural Network by Tariq Rashid. In this work you implement a small neural network by hand. This is for my own benefit and I know if I was doing something for real I should just Flu…

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## [Does delete! or Observable @view work with Axis3?](https://discourse.julialang.org/t/does-delete-or-observable-view-work-with-axis3/94061)

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**Author:** [@g2g](https://discourse.julialang.org/u/g2g)\
**Replies:** 2\
**Last updated:** [February 5, 2023, 8:59pm UTC](https://discourse.julialang.org/t/does-delete-or-observable-view-work-with-axis3/94061 "2023-02-05T20:59:10Z")

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As part of an essay (including a listing of the 3D PGA reference implementation ripga3d.jl in the appendix) proposing that Julia + Makie + projective geometric algebra (PGA) are an excellent combination for implementing …

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## [Solving DDE system using derivative at a previous time](https://discourse.julialang.org/t/solving-dde-system-using-derivative-at-a-previous-time/94015)

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**Author:** [@rogue26](https://discourse.julialang.org/u/rogue26)\
**Replies:** 7\
**Last updated:** [February 5, 2023, 8:03pm UTC](https://discourse.julialang.org/t/solving-dde-system-using-derivative-at-a-previous-time/94015 "2023-02-05T20:03:57Z")

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Hi. I’m trying to figure out to use DifferentialEquations.jl to solve a system of DDEs that depend not only on the values at previous times, but on the time derivatives of those values at previous times. For example, sup…

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## [Is it possible to avoid eval in this code?](https://discourse.julialang.org/t/is-it-possible-to-avoid-eval-in-this-code/93975)

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**Author:** [@Alexander-Barth](https://discourse.julialang.org/u/Alexander-Barth)\
**Replies:** 13\
**Last updated:** [February 5, 2023, 8:03pm UTC](https://discourse.julialang.org/t/is-it-possible-to-avoid-eval-in-this-code/93975 "2023-02-05T20:03:50Z")

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I would like to write a macro which subsets a collection of variables (with shared dimensions). My use case can be simplified to a dictionary of vectors where each vector has the same length, for example: ds = Dict(:a =\>…

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## [Error using @sync/@async within macro, help is highly appreciated](https://discourse.julialang.org/t/error-using-sync-async-within-macro-help-is-highly-appreciated/94080)

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**Author:** [@schlichtanders](https://discourse.julialang.org/u/schlichtanders)\
**Replies:** 2\
**Last updated:** [February 5, 2023, 3:05pm UTC](https://discourse.julialang.org/t/error-using-sync-async-within-macro-help-is-highly-appreciated/94080 "2023-02-05T15:05:09Z")

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Hi there, I would like to write a macro which just waits until a next time, if I run it on my own in a repl, it works, but if I put it into a macro, it fails with ERROR: syntax: invalid let syntax around task.jl:453 h…

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## [A Gentle Guide to Your First JuliaCon Review](https://discourse.julialang.org/t/a-gentle-guide-to-your-first-juliacon-review/93537)

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**Author:** [@TheCedarPrince](https://discourse.julialang.org/u/TheCedarPrince)\
**Replies:** 3\
**Last updated:** [February 5, 2023, 1:20pm UTC](https://discourse.julialang.org/t/a-gentle-guide-to-your-first-juliacon-review/93537 "2023-02-05T13:20:29Z")

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Hi folks! JuliaCon is just around the corner and I wanted to more publicly share this resource I put together for new reviewers of the (fantastic) annual JuliaCon. Hope it helps! As there have been some questions abou…

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## [Makie: get 3D axis limits](https://discourse.julialang.org/t/makie-get-3d-axis-limits/94024)

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**Author:** [@Jollywatt](https://discourse.julialang.org/u/Jollywatt)\
**Replies:** 4\
**Last updated:** [February 5, 2023, 11:18am UTC](https://discourse.julialang.org/t/makie-get-3d-axis-limits/94024 "2023-02-05T11:18:32Z")

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Hi, I can’t for the life of me find I way to retrieve the current axis limits for 3D Makie plots. I can’t even find I nice way to do this for 2D plots, though you can get there with a lot of effort: julia\> scatter(ran…

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## [Makie vlines ymin/ymax](https://discourse.julialang.org/t/makie-vlines-ymin-ymax/94079)

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**Author:** [@jar1](https://discourse.julialang.org/u/jar1)\
**Replies:** 1\
**Last updated:** [February 5, 2023, 9:56am UTC](https://discourse.julialang.org/t/makie-vlines-ymin-ymax/94079 "2023-02-05T09:56:59Z")

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vlines(\[1,2,3,4,5\]; ymin=0, ymax=1) Why does it go from 0 to 10 instead of 0 to 1?

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## [Build Process Question for OpenBLAS](https://discourse.julialang.org/t/build-process-question-for-openblas/94074)

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**Author:** [@bmgroth](https://discourse.julialang.org/u/bmgroth)\
**Replies:** 1\
**Last updated:** [February 5, 2023, 7:35am UTC](https://discourse.julialang.org/t/build-process-question-for-openblas/94074 "2023-02-05T07:35:17Z")

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How does the build process work for OpenBLAS? There are three main files that I know that impact the build: julia/Make.inc + julia/deps/openblas.mk BinaryBuilder + Yggdrasil/O/OpenBLAS/common.jl It seems that all the…

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## [Problem for a system of stochastic differential equations (SDE) with multiple Wiener processes](https://discourse.julialang.org/t/problem-for-a-system-of-stochastic-differential-equations-sde-with-multiple-wiener-processes/93828)

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**Author:** [@canturk](https://discourse.julialang.org/u/canturk)\
**Replies:** 5\
**Last updated:** [February 4, 2023, 10:51pm UTC](https://discourse.julialang.org/t/problem-for-a-system-of-stochastic-differential-equations-sde-with-multiple-wiener-processes/93828 "2023-02-04T22:51:47Z")

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I attempted to solve a system of SDE as in the form below. But I am struggeling with a persisting error message as shown below. A replicated SDE is as follows: Here A, B, C, and D are sparse matrices with size NxN; u…

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## [Random Float64 over whole range of Float64](https://discourse.julialang.org/t/random-float64-over-whole-range-of-float64/94053)

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**Author:** [@natemcintosh](https://discourse.julialang.org/u/natemcintosh)\
**Replies:** 8\
**Last updated:** [February 4, 2023, 7:52pm UTC](https://discourse.julialang.org/t/random-float64-over-whole-range-of-float64/94053 "2023-02-04T19:52:44Z")

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Calling rand(Float64) will generate a random number in the range \[0, 1). However, I want to draw random numbers from all possible Float64 values. Does anyone know of a good way to do this? I feel like I’m just overlookin…

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## [Terminal control characters to xterm/mintty blocked on windows](https://discourse.julialang.org/t/terminal-control-characters-to-xterm-mintty-blocked-on-windows/94006)

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**Author:** [@devel-chm](https://discourse.julialang.org/u/devel-chm)\
**Replies:** 1\
**Last updated:** [February 3, 2023, 11:47pm UTC](https://discourse.julialang.org/t/terminal-control-characters-to-xterm-mintty-blocked-on-windows/94006 "2023-02-03T23:47:41Z")

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For remote computing, I’ve been testing the use of Sixel Graphics to conveniently see graphics in-line with a terminal session of some sort (e.g., xterm or vt340). This worked well on unix systems but when I tried thi…

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## [Paste strings in \`Cmd\`](https://discourse.julialang.org/t/paste-strings-in-cmd/94050)

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**Author:** [@Rex\_Wang](https://discourse.julialang.org/u/Rex_Wang)\
**Replies:** 1\
**Last updated:** [February 4, 2023, 3:50pm UTC](https://discourse.julialang.org/t/paste-strings-in-cmd/94050 "2023-02-04T15:50:57Z")

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To avoid XY problem, I’ll describe the problem that needs to be solved first. After building a JLL package, one can use run(\`$(product\_name()) $args\`) to wrap an executable. (Then use execute to collect the results as…

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## [How to plot a 3D plot of 3 inequalities?](https://discourse.julialang.org/t/how-to-plot-a-3d-plot-of-3-inequalities/93910)

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**Author:** [@Kanishk](https://discourse.julialang.org/u/Kanishk)\
**Replies:** 10\
**Last updated:** [February 4, 2023, 12:32pm UTC](https://discourse.julialang.org/t/how-to-plot-a-3d-plot-of-3-inequalities/93910 "2023-02-04T12:32:25Z")

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Hello I have 3 inequalities and each have 3 variables. Could you please explain how can I draw a combined one 3D plot with shaded area satisfying all the 3 inequalities? I have inequalities of the form as f1(x,y,z) = a…

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## [Combine \`HTTP.Response\` to \`HTTP.Stream\` handlers within one server in HTTP.jl](https://discourse.julialang.org/t/combine-http-response-to-http-stream-handlers-within-one-server-in-http-jl/93985)

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**Author:** [@sairus7](https://discourse.julialang.org/u/sairus7)\
**Replies:** 1\
**Last updated:** [February 4, 2023, 3:58am UTC](https://discourse.julialang.org/t/combine-http-response-to-http-stream-handlers-within-one-server-in-http-jl/93985 "2023-02-04T03:58:00Z")

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What is the replacement for HTTP.Handlers.StreamHandlerFunction in post 1.0 HTTP.jl package? I have a server that handles requests, but with a single endpoint with streaming HTTP connection, in 0.9 I could just write th…

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## [Custom Julia system image](https://discourse.julialang.org/t/custom-julia-system-image/94026)

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**Author:** [@A\_M](https://discourse.julialang.org/u/A_M)\
**Replies:** 0\
**Last updated:** [February 4, 2023, 12:06am UTC](https://discourse.julialang.org/t/custom-julia-system-image/94026 "2023-02-04T00:06:18Z")

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I am trying to create a system image for a specific project (Project.toml) using python -m julia.sysimage sys.so How can I enforce those packages to be part of the system image? If the system image has only PyCall and …

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