# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1061

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

**Page:** 1062

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## [What's the most efficient way to compute the matrix product A'\*B\*A for general B?](https://discourse.julialang.org/t/whats-the-most-efficient-way-to-compute-the-matrix-product-a-b-a-for-general-b/79821)

<div class="topic-metadata">

**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 5\
**Last updated:** [April 23, 2022, 11:39am UTC](https://discourse.julialang.org/t/whats-the-most-efficient-way-to-compute-the-matrix-product-a-b-a-for-general-b/79821 "2022-04-23T11:39:13Z")

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The matrix A has orthonormal columns, but is rectangular (tall). Currently, I allocate caches C and D, and evaluate mul!(D, A', mul!(C, B, A) In my use case, A and B are somewhat large matrices, so I’d ideally like to …

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## [Sampler for arbitrary univariate distribution?](https://discourse.julialang.org/t/sampler-for-arbitrary-univariate-distribution/41538)

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**Author:** [@oschulz](https://discourse.julialang.org/u/oschulz)\
**Replies:** 8\
**Last updated:** [April 23, 2022, 9:48am UTC](https://discourse.julialang.org/t/sampler-for-arbitrary-univariate-distribution/41538 "2022-04-23T09:48:16Z")

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Do we have a sampler for arbitrary univariate distributions implemented somewhere (Ziggurat algorithm or so)?

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## [Adopt COM-Server Wrapper from Python to Julia](https://discourse.julialang.org/t/adopt-com-server-wrapper-from-python-to-julia/79853)

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**Author:** [@ellocco](https://discourse.julialang.org/u/ellocco)\
**Replies:** 3\
**Last updated:** [April 23, 2022, 7:00am UTC](https://discourse.julialang.org/t/adopt-com-server-wrapper-from-python-to-julia/79853 "2022-04-23T07:00:59Z")

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Hi, Under python the script „makepy.py“ exists, it generates a wrapper for a specified COM-server. I wonder, can this wrapper code be rewritten in Julia-Style? If there is someone who offers such a service on the basi…

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## [\[ANN\] jill.py -- a simple and stupid cross-platform Julia installer](https://discourse.julialang.org/t/ann-jill-py-a-simple-and-stupid-cross-platform-julia-installer/34845)

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**Author:** [@JohnnyChen94](https://discourse.julialang.org/u/JohnnyChen94)\
**Replies:** 10\
**Last updated:** [April 23, 2022, 3:35am UTC](https://discourse.julialang.org/t/ann-jill-py-a-simple-and-stupid-cross-platform-julia-installer/34845 "2022-04-23T03:35:49Z")

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The python fork jill.py is a cross-platform Julia installer that provides more functionalities than the original bash script made by @abelsiqueira : download the latest Julia release from the nearest mirror server keep…

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## [Literate and Artifacts](https://discourse.julialang.org/t/literate-and-artifacts/79808)

<div class="topic-metadata">

**Author:** [@cortner](https://discourse.julialang.org/u/cortner)\
**Replies:** 6\
**Last updated:** [April 23, 2022, 3:15am UTC](https://discourse.julialang.org/t/literate-and-artifacts/79808 "2022-04-23T03:15:53Z")

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I seem to be unable to use Literate when the script I’m trying to convert tries to load an artifact. The full setup - all files in the same folder - is printed at the bottom of this post. If I execute the script by act…

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## [How can I detect Apple M1 chip?](https://discourse.julialang.org/t/how-can-i-detect-apple-m1-chip/79870)

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**Author:** [@chkwon](https://discourse.julialang.org/u/chkwon)\
**Replies:** 2\
**Last updated:** [April 23, 2022, 2:59am UTC](https://discourse.julialang.org/t/how-can-i-detect-apple-m1-chip/79870 "2022-04-23T02:59:21Z")

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I need to provide different build scripts for Apple Intel and Apple M1. How can I detect M1? Can Sys.isapple() or any other method distinguish them?

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## [Unicode symbols as arrowheads in Makie](https://discourse.julialang.org/t/unicode-symbols-as-arrowheads-in-makie/79039)

<div class="topic-metadata">

**Author:** [@kfrb](https://discourse.julialang.org/u/kfrb)\
**Replies:** 3\
**Last updated:** [April 22, 2022, 9:34pm UTC](https://discourse.julialang.org/t/unicode-symbols-as-arrowheads-in-makie/79039 "2022-04-22T21:34:12Z")

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Is it possible to use other Symbols for the arrowheads in Makie? According to the docs, the arrowhead attribute is set by default to automatic, which is in 2D the symbol "▲". To use something like arrowhead="△" could be …

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## [Debugger for command line script (works without REPL)?](https://discourse.julialang.org/t/debugger-for-command-line-script-works-without-repl/60286)

<div class="topic-metadata">

**Author:** [@mkarikom](https://discourse.julialang.org/u/mkarikom)\
**Replies:** 0\
**Last updated:** [April 30, 2021, 2:29am UTC](https://discourse.julialang.org/t/debugger-for-command-line-script-works-without-repl/60286 "2021-04-30T02:29:49Z")

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Is there a debugger that will allow me to do something like this: JULIA\_PROJECT=/tmp/testenv julia /tmp/testenv/testdebugger.jl hithere # testdebugger.jl (does not work) println(string("julia environment is:\\n ",ENV\["J…

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## [Export/import color matrix](https://discourse.julialang.org/t/export-import-color-matrix/79861)

<div class="topic-metadata">

**Author:** [@ahmed](https://discourse.julialang.org/u/ahmed)\
**Replies:** 1\
**Last updated:** [April 22, 2022, 6:32pm UTC](https://discourse.julialang.org/t/export-import-color-matrix/79861 "2022-04-22T18:32:24Z")

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I have a matrix of colors of the type RGB{float 64}. I’d like to export this matrix from julia to a file and then import it back to julia to do further analysis. I tried using DelimitedFiles this way: writedlm(“colors.t…

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## [Julia 1.6 precompiling project, dependency skipped due to previous error - which one?](https://discourse.julialang.org/t/julia-1-6-precompiling-project-dependency-skipped-due-to-previous-error-which-one/53322)

<div class="topic-metadata">

**Author:** [@jdad](https://discourse.julialang.org/u/jdad)\
**Replies:** 4\
**Last updated:** [April 22, 2022, 6:17pm UTC](https://discourse.julialang.org/t/julia-1-6-precompiling-project-dependency-skipped-due-to-previous-error-which-one/53322 "2022-04-22T18:17:47Z")

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During update of julia 1.6.0, while precompiling the project, I get indication of (previous) failed module precompilation. (@v1.6) pkg\> up Updating registry at \`C:\\Users\\davidj\\.julia\\registries\\General\` Updatin…

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## [Compute simplex tableau from Gurobi.jl using JuMP](https://discourse.julialang.org/t/compute-simplex-tableau-from-gurobi-jl-using-jump/79395)

<div class="topic-metadata">

**Author:** [@jacob-roth](https://discourse.julialang.org/u/jacob-roth)\
**Replies:** 2\
**Last updated:** [April 22, 2022, 6:08pm UTC](https://discourse.julialang.org/t/compute-simplex-tableau-from-gurobi-jl-using-jump/79395 "2022-04-22T18:08:13Z")

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I am modeling an LP in JuMP using Gurobi. How can I obtain the optimal simplex tableau? For example, consider the below LP: A = \[1; 2; 3\]' c = \[4; 5; 6\] b = 7 M = Model(Gurobi.Optimizer) set\_optimizer\_attribute(M, "Pre…

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## [GMRES (krylovkit) info.residual](https://discourse.julialang.org/t/gmres-krylovkit-info-residual/79860)

<div class="topic-metadata">

**Author:** [@Srikumar](https://discourse.julialang.org/u/Srikumar)\
**Replies:** 0\
**Last updated:** [April 22, 2022, 6:12pm UTC](https://discourse.julialang.org/t/gmres-krylovkit-info-residual/79860 "2022-04-22T18:12:54Z")

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I find that the norm(info.residual) that GMRES prints at each step (inside a single iteration) is different from the actual residual norm ||(b-Ax)|| that one computes with the current approximate x manually. Are these 2 …

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## [Why Julia is very often related to a data science / economics language only?](https://discourse.julialang.org/t/why-julia-is-very-often-related-to-a-data-science-economics-language-only/79695)

<div class="topic-metadata">

**Author:** [@Ronis\_BR](https://discourse.julialang.org/u/Ronis_BR)\
**Replies:** 46\
**Last updated:** [April 22, 2022, 5:10pm UTC](https://discourse.julialang.org/t/why-julia-is-very-often-related-to-a-data-science-economics-language-only/79695 "2022-04-22T17:10:06Z")

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Hi! This post is just a Tuesday morning thinking… Why almost all the time I saw a comment about Julia on LinkedIn or some other forum, it is treated as a data science / big data / economics language?! Where did this co…

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## [Repl debugger how to set default editor?](https://discourse.julialang.org/t/repl-debugger-how-to-set-default-editor/79851)

<div class="topic-metadata">

**Author:** [@anon69491625](https://discourse.julialang.org/u/anon69491625)\
**Replies:** 2\
**Last updated:** [April 22, 2022, 5:02pm UTC](https://discourse.julialang.org/t/repl-debugger-how-to-set-default-editor/79851 "2022-04-22T17:02:55Z")

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hi there just starting with the julia repl debugger but when I want to open the current line in an editor I get About to run: (tuple)(2, 2) 1|debug\> fr \[1\] foo(n) at REPL\[1\]:1 | n::Int64 = 20 | x::Int64 = 21 1|debu…

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## [GLMakie - Connecting a Slider to update images in an axis](https://discourse.julialang.org/t/glmakie-connecting-a-slider-to-update-images-in-an-axis/79847)

<div class="topic-metadata">

**Author:** [@fmc5](https://discourse.julialang.org/u/fmc5)\
**Replies:** 2\
**Last updated:** [April 22, 2022, 4:58pm UTC](https://discourse.julialang.org/t/glmakie-connecting-a-slider-to-update-images-in-an-axis/79847 "2022-04-22T16:58:52Z")

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Hi everyone, I am new to Julia and I am trying to create an interface to show for images (as you can see in the figure). I was able to connect the Slider with the red lines and put the limits of the top left image. But…

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## [Frustrated using DataFrames](https://discourse.julialang.org/t/frustrated-using-dataframes/67833)

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**Author:** [@Nathan\_Boyer](https://discourse.julialang.org/u/Nathan_Boyer)\
**Replies:** 97\
**Last updated:** [April 22, 2022, 4:09pm UTC](https://discourse.julialang.org/t/frustrated-using-dataframes/67833 "2022-04-22T16:09:31Z")

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Overview DataFrames.jl seems to be the preferred way to work with tabular data in Julia, but it never does what I want the first time. The syntax I need to contrive to do things I think would be simple is mind-boggling, …

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## [Copy\_model() equivalent for BilevelJuMP.jl](https://discourse.julialang.org/t/copy-model-equivalent-for-bileveljump-jl/79709)

<div class="topic-metadata">

**Author:** [@math\_opt](https://discourse.julialang.org/u/math_opt)\
**Replies:** 10\
**Last updated:** [April 22, 2022, 3:46pm UTC](https://discourse.julialang.org/t/copy-model-equivalent-for-bileveljump-jl/79709 "2022-04-22T15:46:55Z")

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Is there a way to copy a JuMP model and use it as a building block for the lower level problem in BilevelJuMP.jl. For example: using JuMP, BilevelJuMP model = Model() @variable(model, ...) @constraint(model, ...) #Defi…

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## [MLJ compain TypeError: non-boolean (Nothing) used in boolean context](https://discourse.julialang.org/t/mlj-compain-typeerror-non-boolean-nothing-used-in-boolean-context/79844)

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**Author:** [@tiZ](https://discourse.julialang.org/u/tiZ)\
**Replies:** 0\
**Last updated:** [April 22, 2022, 2:17pm UTC](https://discourse.julialang.org/t/mlj-compain-typeerror-non-boolean-nothing-used-in-boolean-context/79844 "2022-04-22T14:17:27Z")

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Hi, I have trouble in understand the error while I do the model evaluate in MLJ package. I could run succussful with Accuracy or MulticlassFScore measures, but if I add the confusion\_matrix measure as below, it will …

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## [Complementarity constraints containing sum statements](https://discourse.julialang.org/t/complementarity-constraints-containing-sum-statements/79818)

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**Author:** [@rubenvanbeesten](https://discourse.julialang.org/u/rubenvanbeesten)\
**Replies:** 4\
**Last updated:** [April 22, 2022, 2:09pm UTC](https://discourse.julialang.org/t/complementarity-constraints-containing-sum-statements/79818 "2022-04-22T14:09:42Z")

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Hi, I’m trying to model an mathematical program with equilibrium constraints (MPEC) in Julia/JuMP. I am currently using the Complementarity.jl package. I am following this example (“bard1”) and try to adapt it to my nee…

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## [Is Julia integral calculation not as fast as MATLAB?](https://discourse.julialang.org/t/is-julia-integral-calculation-not-as-fast-as-matlab/79824)

<div class="topic-metadata">

**Author:** [@F-YF](https://discourse.julialang.org/u/F-YF)\
**Replies:** 20\
**Last updated:** [April 22, 2022, 2:08pm UTC](https://discourse.julialang.org/t/is-julia-integral-calculation-not-as-fast-as-matlab/79824 "2022-04-22T14:08:34Z")

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I found it was slow when I used QuadGK.jl to do integral calculation. Then I used MATLAB to make a comparison and found that Julia integral was slower than MATLAB. Here are my comparisons: julia\> using QuadGK julia\> f(…

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## [Avoid printout to REPL/console of running a command](https://discourse.julialang.org/t/avoid-printout-to-repl-console-of-running-a-command/79843)

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**Author:** [@bernhard](https://discourse.julialang.org/u/bernhard)\
**Replies:** 1\
**Last updated:** [April 22, 2022, 1:54pm UTC](https://discourse.julialang.org/t/avoid-printout-to-repl-console-of-running-a-command/79843 "2022-04-22T13:54:28Z")

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I am on Windows and vs code. The snippet below prints a ton of verbose mixtex code to the console. I thought read would circumvent this, but that is not the case. Any ideas how I can disable this? I am looking for a …

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## [Printing of unsigned numbers](https://discourse.julialang.org/t/printing-of-unsigned-numbers/79611)

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**Author:** [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Replies:** 29\
**Last updated:** [April 22, 2022, 1:53pm UTC](https://discourse.julialang.org/t/printing-of-unsigned-numbers/79611 "2022-04-22T13:53:11Z")

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One of the common uses of unsigned numbers is as bitmasks. I would be greatly annoyed if they did not print as hexadecimals, as that is exactly what I need them for. And that seems to be fairly common in other languages …

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## [Speed up for-loop with multithreading](https://discourse.julialang.org/t/speed-up-for-loop-with-multithreading/79823)

<div class="topic-metadata">

**Author:** [@Himbeersternchen](https://discourse.julialang.org/u/Himbeersternchen)\
**Replies:** 10\
**Last updated:** [April 22, 2022, 1:32pm UTC](https://discourse.julialang.org/t/speed-up-for-loop-with-multithreading/79823 "2022-04-22T13:32:50Z")

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Hi Guys, I’m trying to speed up my for-loop with multithreading like following (test3.jl code): time0 = @elapsed begin n = 250 a1 = Array{Array{Float64, 1}, 1}(undef, n) Threads.@threads for i in 1:n …

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## [Create a custom Random.Sampler or Matrix sampler via Distribution.Sampleable](https://discourse.julialang.org/t/create-a-custom-random-sampler-or-matrix-sampler-via-distribution-sampleable/79834)

<div class="topic-metadata">

**Author:** [@dmetivie](https://discourse.julialang.org/u/dmetivie)\
**Replies:** 0\
**Last updated:** [April 22, 2022, 12:30pm UTC](https://discourse.julialang.org/t/create-a-custom-random-sampler-or-matrix-sampler-via-distribution-sampleable/79834 "2022-04-22T12:30:14Z")

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I am trying to define rand methods to “randomize” points x represented in a matrix (n, s) (n is the number of point and s is the dimension). I could directly define function rand(RM::RandomizationMethod) x = RM.x …

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## [Registering the user-defined function "multivariate normal cdf" for nonlinear modeling in JuMP](https://discourse.julialang.org/t/registering-the-user-defined-function-multivariate-normal-cdf-for-nonlinear-modeling-in-jump/79825)

<div class="topic-metadata">

**Author:** [@naouess](https://discourse.julialang.org/u/naouess)\
**Replies:** 3\
**Last updated:** [April 22, 2022, 11:46am UTC](https://discourse.julialang.org/t/registering-the-user-defined-function-multivariate-normal-cdf-for-nonlinear-modeling-in-jump/79825 "2022-04-22T11:46:16Z")

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Hello Julia-community, I would like to use the multivariate normal cumulative distribution function within a constraint in JuMP. For the function, I’m using the mvnormcdf from this package MvNormalCDF.jl. Since this re…

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## [Why assuming floating-point rounding errors are random is bad](https://discourse.julialang.org/t/why-assuming-floating-point-rounding-errors-are-random-is-bad/70647)

<div class="topic-metadata">

**Author:** [@ettersi](https://discourse.julialang.org/u/ettersi)\
**Replies:** 14\
**Last updated:** [April 22, 2022, 11:46am UTC](https://discourse.julialang.org/t/why-assuming-floating-point-rounding-errors-are-random-is-bad/70647 "2022-04-22T11:46:05Z")

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This topic continues a discussion started in another topic here on discourse. The goal here is to assemble a list of potential issues which may arise if you assume floating-point rounding errors are random rather than d…

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## [Problems installing QML on M1 machine](https://discourse.julialang.org/t/problems-installing-qml-on-m1-machine/79742)

<div class="topic-metadata">

**Author:** [@f.ij](https://discourse.julialang.org/u/f.ij)\
**Replies:** 17\
**Last updated:** [April 22, 2022, 11:08am UTC](https://discourse.julialang.org/t/problems-installing-qml-on-m1-machine/79742 "2022-04-22T11:08:48Z")

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I’ve been trying to install QML on my M1 MacBook Pro. However, it always fails at the precompiling step. I get the following error: ERROR: LoadError: UndefVarError: libjlqml not defined Stacktrace: \[1\] top-level scope …

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## [Prevent canonical form for complex equations in Symbolics.jl](https://discourse.julialang.org/t/prevent-canonical-form-for-complex-equations-in-symbolics-jl/79800)

<div class="topic-metadata">

**Author:** [@Sciemon](https://discourse.julialang.org/u/Sciemon)\
**Replies:** 2\
**Last updated:** [April 22, 2022, 9:26am UTC](https://discourse.julialang.org/t/prevent-canonical-form-for-complex-equations-in-symbolics-jl/79800 "2022-04-22T09:26:37Z")

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Symbolics.jl brings expressions to a canonical form by default (see also this discussion). Recently a new type of variable (::LiteralReal) was implemented to prevent this so you can keep the expression as it is (see here)…

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## [How to change Makie contourf line color](https://discourse.julialang.org/t/how-to-change-makie-contourf-line-color/79794)

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**Author:** [@LaurentPlagne](https://discourse.julialang.org/u/LaurentPlagne)\
**Replies:** 2\
**Last updated:** [April 22, 2022, 9:08am UTC](https://discourse.julialang.org/t/how-to-change-makie-contourf-line-color/79794 "2022-04-22T09:08:16Z")

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Hi, Does anyone knows how to control the contourf line color and width (I do not find the default one visible enough). Note that I have tried to overlay call to contour with the same arguments but, for some reasons,…

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## [Package for sampling from a uniform distribution over a convex polytope?](https://discourse.julialang.org/t/package-for-sampling-from-a-uniform-distribution-over-a-convex-polytope/18598)

<div class="topic-metadata">

**Author:** [@ajkeith](https://discourse.julialang.org/u/ajkeith)\
**Replies:** 3\
**Last updated:** [April 22, 2022, 8:37am UTC](https://discourse.julialang.org/t/package-for-sampling-from-a-uniform-distribution-over-a-convex-polytope/18598 "2022-04-22T08:37:23Z")

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Is there a Julia package for sampling from a uniform distribution over a convex polytope? I’m trying to sample a categorical distribution from an ambiguity set of categorical distributions subject to linear constraints.…

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