# Latest

**URL:** https://discourse.julialang.org/latest.md?page=871

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

**Page:** 872

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## [Data stitching](https://discourse.julialang.org/t/data-stitching/89662)

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**Author:** [@gustaphe](https://discourse.julialang.org/u/gustaphe)\
**Replies:** 30\
**Last updated:** [November 7, 2022, 10:10pm UTC](https://discourse.julialang.org/t/data-stitching/89662 "2022-11-07T22:10:48Z")

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I’m looking for a package or an algorithm, alternatively an explanation of why what I want is impossible or bad: I have a set of data x1, y1 ≈ f.(x1) and one x2, y2 ≈ a\*f.(x2) .+ b for some natural black box function f …

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## [How to set multiple arrays from a single array?](https://discourse.julialang.org/t/how-to-set-multiple-arrays-from-a-single-array/89851)

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**Author:** [@zxm403089989](https://discourse.julialang.org/u/zxm403089989)\
**Replies:** 6\
**Last updated:** [November 7, 2022, 10:16pm UTC](https://discourse.julialang.org/t/how-to-set-multiple-arrays-from-a-single-array/89851 "2022-11-07T22:16:00Z")

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Is there any way to directly define new array from a known larger array? For example: a1,a2=\[1 2;3 4\] 2×2 Matrix{Int64}: 1 2 3 4 a1 1 a2 2 This doesn’t give results I need. However, if I set array from a vector of …

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## [Packages for Fluid Simulations and Modelling?](https://discourse.julialang.org/t/packages-for-fluid-simulations-and-modelling/89882)

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**Author:** [@wali\_waqar](https://discourse.julialang.org/u/wali_waqar)\
**Replies:** 1\
**Last updated:** [November 7, 2022, 9:34pm UTC](https://discourse.julialang.org/t/packages-for-fluid-simulations-and-modelling/89882 "2022-11-07T21:34:36Z")

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Hi, I have to simulate Faraday Waves and Faraday Instability in floating droplets for a project that I’m doing, and I really wanted to use Julia for the task. Are there any packages that I could be of use to me?

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## [Set\_optimizer\_attribute does not work in newer versions of JuMP, Julia, etc.?](https://discourse.julialang.org/t/set-optimizer-attribute-does-not-work-in-newer-versions-of-jump-julia-etc/89727)

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**Author:** [@fksayaci](https://discourse.julialang.org/u/fksayaci)\
**Replies:** 8\
**Last updated:** [November 7, 2022, 9:14pm UTC](https://discourse.julialang.org/t/set-optimizer-attribute-does-not-work-in-newer-versions-of-jump-julia-etc/89727 "2022-11-07T21:14:10Z")

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Hello all, I have an optimization model. I run it on my computer without any problem. I have the following for loop to assign values to Gurobi parameters: for paramrow in eachrow(solver\_params) if paramrow.Type == …

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## [My mental load using Julia is much higher than, e.g., in Python. How to reduce it?](https://discourse.julialang.org/t/my-mental-load-using-julia-is-much-higher-than-e-g-in-python-how-to-reduce-it/18902)

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**Author:** [@jules](https://discourse.julialang.org/u/jules)\
**Replies:** 50\
**Last updated:** [November 7, 2022, 9:03pm UTC](https://discourse.julialang.org/t/my-mental-load-using-julia-is-much-higher-than-e-g-in-python-how-to-reduce-it/18902 "2022-11-07T21:03:11Z")

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Hi, I’m new to the language, and although I like so many aspects of Julia, I am struggling to start using it. I come from Python mostly, but have been looking for an alternative in which low-level function speed can be …

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## [DataFrame colon : vs bang ! indexing](https://discourse.julialang.org/t/dataframe-colon-vs-bang-indexing/89901)

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**Author:** [@chadagreene](https://discourse.julialang.org/u/chadagreene)\
**Replies:** 4\
**Last updated:** [November 7, 2022, 8:56pm UTC](https://discourse.julialang.org/t/dataframe-colon-vs-bang-indexing/89901 "2022-11-07T20:56:21Z")

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I’m learning about DataFrames right now, and I’ve seen some cases where columns are accessed with a bang ! where I’d expect a colon. Here’s an example: julia\> df = DataFrame(name=\["Sally", "Bob", "Alice", "Frank"\], age=…

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## [How to use Logging.jl?](https://discourse.julialang.org/t/how-to-use-logging-jl/89908)

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**Author:** [@fksayaci](https://discourse.julialang.org/u/fksayaci)\
**Replies:** 0\
**Last updated:** [November 7, 2022, 8:42pm UTC](https://discourse.julialang.org/t/how-to-use-logging-jl/89908 "2022-11-07T20:42:51Z")

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Hi all, We have an optimization model, which I can run successfully in my local computer and my HPC cluster account. My colleague in our research group recently installed Gurobi, Julia, and JuMP in his HPC cluster accou…

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## [Plots.jl @layout specify width dynamically](https://discourse.julialang.org/t/plots-jl-layout-specify-width-dynamically/21017)

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**Author:** [@nathancunn](https://discourse.julialang.org/u/nathancunn)\
**Replies:** 1\
**Last updated:** [November 7, 2022, 8:25pm UTC](https://discourse.julialang.org/t/plots-jl-layout-specify-width-dynamically/21017 "2022-11-07T20:25:15Z")

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I assume this has a very simple solution, but I’m struggling. I’m trying to set up a grid of plots with a non-standard layout using Plots.jl which I can do as follows: x = rand(100, 4) l = @layout \[a{0.8w} grid(3, 1)\] …

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## [Plots: subplot size changes when nesting plots with subplots & layout](https://discourse.julialang.org/t/plots-subplot-size-changes-when-nesting-plots-with-subplots-layout/61287)

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**Author:** [@vandenman](https://discourse.julialang.org/u/vandenman)\
**Replies:** 0\
**Last updated:** [May 17, 2021, 9:14am UTC](https://discourse.julialang.org/t/plots-subplot-size-changes-when-nesting-plots-with-subplots-layout/61287 "2021-05-17T09:14:32Z")

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So I’m having an issue when I put a plot with a layout into another plot. Consider the following example, my actual code is different (e.g., more pretty plotting and meaningful content), but this shows the problem alrea…

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## [Optimizer in Evolutionary.jl returns initial conditions as minimizer with default setting](https://discourse.julialang.org/t/optimizer-in-evolutionary-jl-returns-initial-conditions-as-minimizer-with-default-setting/89902)

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**Author:** [@mylo19](https://discourse.julialang.org/u/mylo19)\
**Replies:** 1\
**Last updated:** [November 7, 2022, 7:33pm UTC](https://discourse.julialang.org/t/optimizer-in-evolutionary-jl-returns-initial-conditions-as-minimizer-with-default-setting/89902 "2022-11-07T19:33:57Z")

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I want to use a genetic algorithm to minimize a function. After searching, I read that the best available option is Evolutionary.jl. Hence, I started reading the documentation. I tried running the examples found in the t…

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## [Layout with several grids](https://discourse.julialang.org/t/layout-with-several-grids/87474)

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**Author:** [@Gregstrq](https://discourse.julialang.org/u/Gregstrq)\
**Replies:** 2\
**Last updated:** [November 7, 2022, 7:23pm UTC](https://discourse.julialang.org/t/layout-with-several-grids/87474 "2022-11-07T19:23:12Z")

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I am using Plots with GR backend and trying to create a 2x2 grid of plots with a common legend in the bottom. As it happens, there is no support for horizontal legends with gr, so I am trying to add plots without a fram…

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## [MethodError: no method matching Float64 when using ForwardDiff.jl despite me pre-allocating arrays to take floating point](https://discourse.julialang.org/t/methoderror-no-method-matching-float64-when-using-forwarddiff-jl-despite-me-pre-allocating-arrays-to-take-floating-point/89859)

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**Author:** [@sumant28](https://discourse.julialang.org/u/sumant28)\
**Replies:** 4\
**Last updated:** [November 7, 2022, 7:07pm UTC](https://discourse.julialang.org/t/methoderror-no-method-matching-float64-when-using-forwarddiff-jl-despite-me-pre-allocating-arrays-to-take-floating-point/89859 "2022-11-07T19:07:31Z")

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using Optimization, OptimizationOptimJL, OptimizationBBO, OptimizationMOI, ForwardDiff, ModelingToolkit, Random, OptimizationOptimisers, Statistics, Plots function MSEg(u, p) X = p.X y = p.y h = u\[1\] beta = u\[2:…

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## [Julia at CSCS Switzerland](https://discourse.julialang.org/t/julia-at-cscs-switzerland/89898)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 2\
**Last updated:** [November 7, 2022, 6:15pm UTC](https://discourse.julialang.org/t/julia-at-cscs-switzerland/89898 "2022-11-07T18:15:58Z")

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Really interesting article. Is Sebin John on here?

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## [Take a derivative with respect to an expression in Symbolics](https://discourse.julialang.org/t/take-a-derivative-with-respect-to-an-expression-in-symbolics/89900)

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**Author:** [@brianguenter](https://discourse.julialang.org/u/brianguenter)\
**Replies:** 0\
**Last updated:** [November 7, 2022, 6:05pm UTC](https://discourse.julialang.org/t/take-a-derivative-with-respect-to-an-expression-in-symbolics/89900 "2022-11-07T18:05:27Z")

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The Symbolics documentation says (bold italic emphasis added) struct Differential \<: Symbolics.Operator Represents a differential operator. Fields x : The variable or expression to differentiate with respect to. T…

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## [What are Julia's coordinates in the λ-cube?](https://discourse.julialang.org/t/what-are-julias-coordinates-in-the-cube/89883)

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**Author:** [@cdawg](https://discourse.julialang.org/u/cdawg)\
**Replies:** 6\
**Last updated:** [November 7, 2022, 4:51pm UTC](https://discourse.julialang.org/t/what-are-julias-coordinates-in-the-cube/89883 "2022-11-07T16:51:51Z")

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I was sidetracked procrastinating reading a thread about using “{}”. here and popping out a new thread. My vote was to make where statements more expressive by doing type calculations inside blocks deliminated by {} so …

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## [ArpackBuilder gone, Arpack v0.3.1 build fails for Julia 1.0.\*](https://discourse.julialang.org/t/arpackbuilder-gone-arpack-v0-3-1-build-fails-for-julia-1-0/89869)

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**Author:** [@HanD](https://discourse.julialang.org/u/HanD)\
**Replies:** 9\
**Last updated:** [November 7, 2022, 4:10pm UTC](https://discourse.julialang.org/t/arpackbuilder-gone-arpack-v0-3-1-build-fails-for-julia-1-0/89869 "2022-11-07T16:10:13Z")

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We have been using Julia 1.0.\* for a legacy project for quite some time. The program relies on the MultivariateStats package, which in turn uses Arpack v0.3.1. This version of Arpack relies on ArpackBuilder, or rather, r…

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## [Multiplication of vector of matrices and vector of vectors](https://discourse.julialang.org/t/multiplication-of-vector-of-matrices-and-vector-of-vectors/89874)

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**Author:** [@dalbandea](https://discourse.julialang.org/u/dalbandea)\
**Replies:** 3\
**Last updated:** [November 7, 2022, 3:59pm UTC](https://discourse.julialang.org/t/multiplication-of-vector-of-matrices-and-vector-of-vectors/89874 "2022-11-07T15:59:50Z")

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I’m trying to optimize a multiplication of a vector of Matrices A of size (L, L, L) and a vector of vectors x of size (L,L), which will result in a vector of vectors c of size (L, L). That is, each c\[i,:\] is the result …

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## [T Distribution - Automatic Differentiation on quantile and cdf function](https://discourse.julialang.org/t/t-distribution-automatic-differentiation-on-quantile-and-cdf-function/89434)

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**Author:** [@mrVeng](https://discourse.julialang.org/u/mrVeng)\
**Replies:** 9\
**Last updated:** [November 7, 2022, 3:42pm UTC](https://discourse.julialang.org/t/t-distribution-automatic-differentiation-on-quantile-and-cdf-function/89434 "2022-11-07T15:42:02Z")

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Hi there, I need to use the cdf (and quantile) function of the T distribution inside a function that I want to use Automatic Differentiation on. This works fine with almost any univariate distribution from the Distribut…

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## [\[ANN\] Package Triad: Dynamics of Value Evolution](https://discourse.julialang.org/t/ann-package-triad-dynamics-of-value-evolution/89885)

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**Author:** [@thevolatilebit](https://discourse.julialang.org/u/thevolatilebit)\
**Replies:** 0\
**Last updated:** [November 7, 2022, 3:03pm UTC](https://discourse.julialang.org/t/ann-package-triad-dynamics-of-value-evolution/89885 "2022-11-07T15:03:36Z")

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We are excited to announce the release of DyVE, a Julia framework for computational value dynamics. The acronym stands for Dynamics of Value Evolution. DyVE is aimed at designing, fitting, and integrating dynamical mod…

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## [Julia plots are very slow in every run](https://discourse.julialang.org/t/julia-plots-are-very-slow-in-every-run/89863)

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**Author:** [@Fuad\_Hasibul\_Hasan](https://discourse.julialang.org/u/Fuad_Hasibul_Hasan)\
**Replies:** 5\
**Last updated:** [November 7, 2022, 2:24pm UTC](https://discourse.julialang.org/t/julia-plots-are-very-slow-in-every-run/89863 "2022-11-07T14:24:54Z")

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I am relatively new to Julia. I find plotting very slow; though I found some questions and responses about slow plotting for the first time due to compilation, in my case it is slow every time. Here is what I am doing: @…

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## [Silhouette coefficient calculation](https://discourse.julialang.org/t/silhouette-coefficient-calculation/89861)

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**Author:** [@Shayan](https://discourse.julialang.org/u/Shayan)\
**Replies:** 5\
**Last updated:** [November 7, 2022, 1:49pm UTC](https://discourse.julialang.org/t/silhouette-coefficient-calculation/89861 "2022-11-07T13:49:47Z")

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I’ve written a Julia script to calculate the silhouette coefficient of the ClusterAnalysis.jl Kmeans’ result, but it’s highly inefficient and slow. I’ve written the procedure for both common and simplified versions of th…

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## [Importing Plots increasing garbage collection](https://discourse.julialang.org/t/importing-plots-increasing-garbage-collection/89878)

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**Author:** [@jewh](https://discourse.julialang.org/u/jewh)\
**Replies:** 3\
**Last updated:** [November 7, 2022, 1:57pm UTC](https://discourse.julialang.org/t/importing-plots-increasing-garbage-collection/89878 "2022-11-07T13:57:01Z")

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It seems that importing Plots is significantly increasing the mean % garbage collection time when executing this function motif2. Does anyone know why, and how to prevent it? julia\> using BenchmarkTools julia\> function…

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## [Recordings of Julia Computing webinars available?](https://discourse.julialang.org/t/recordings-of-julia-computing-webinars-available/89817)

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**Author:** [@pxshen](https://discourse.julialang.org/u/pxshen)\
**Replies:** 7\
**Last updated:** [November 7, 2022, 1:35pm UTC](https://discourse.julialang.org/t/recordings-of-julia-computing-webinars-available/89817 "2022-11-07T13:35:20Z")

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Specifically I registered but missed “Trimming, Linearization, and Model Predictive Control (MPC) Design with JuliaSim” on 11/2. Is there a recording?

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## [Initiate a struct without its name but only by its type in local scope](https://discourse.julialang.org/t/initiate-a-struct-without-its-name-but-only-by-its-type-in-local-scope/89875)

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**Author:** [@elakelaiset](https://discourse.julialang.org/u/elakelaiset)\
**Replies:** 4\
**Last updated:** [November 7, 2022, 1:17pm UTC](https://discourse.julialang.org/t/initiate-a-struct-without-its-name-but-only-by-its-type-in-local-scope/89875 "2022-11-07T13:17:55Z")

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Hi together, i try to define a function which creates a new composite based on a copy of a given composite, but with a single field changed, and without using mutable structs. I’ve attached a code snipped which tries t…

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## [Where does Julia in VS Code specify startup shell commands if not within startup.jl?](https://discourse.julialang.org/t/where-does-julia-in-vs-code-specify-startup-shell-commands-if-not-within-startup-jl/89791)

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**Author:** [@alex-s-gardner](https://discourse.julialang.org/u/alex-s-gardner)\
**Replies:** 2\
**Last updated:** [November 7, 2022, 12:10pm UTC](https://discourse.julialang.org/t/where-does-julia-in-vs-code-specify-startup-shell-commands-if-not-within-startup-jl/89791 "2022-11-07T12:10:58Z")

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For some reason when the Julia REPL starts within VSCode when I hit shift-enter on my first line of Julia code a = 1 contained within a .jl file I get: source /Users/gardnera/tools/miniconda3/bin/activate julia\> urce /U…

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## [Usage of lazy vector instead of function](https://discourse.julialang.org/t/usage-of-lazy-vector-instead-of-function/89766)

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**Author:** [@Salmon](https://discourse.julialang.org/u/Salmon)\
**Replies:** 22\
**Last updated:** [November 7, 2022, 10:37am UTC](https://discourse.julialang.org/t/usage-of-lazy-vector-instead-of-function/89766 "2022-11-07T10:37:22Z")

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Hi everyone, recently I stumbled across a nice benchmark between different languages and was having a look at the Julia implementation: Now in general, I understand why there is a use case for lazy arrays, but is this…

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## [How to save two overlapped plots together in one single file?](https://discourse.julialang.org/t/how-to-save-two-overlapped-plots-together-in-one-single-file/89852)

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**Author:** [@mzd1893](https://discourse.julialang.org/u/mzd1893)\
**Replies:** 3\
**Last updated:** [November 7, 2022, 8:42am UTC](https://discourse.julialang.org/t/how-to-save-two-overlapped-plots-together-in-one-single-file/89852 "2022-11-07T08:42:51Z")

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using Plots plot(0:10,sin); plot!(0:10,sin,seriestype = :scatter) In this example, the output are actually two plots. How can I save them in one file?

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## [Symbolics not simplifying fully](https://discourse.julialang.org/t/symbolics-not-simplifying-fully/89842)

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**Author:** [@AwesomeQuest](https://discourse.julialang.org/u/AwesomeQuest)\
**Replies:** 3\
**Last updated:** [November 7, 2022, 6:27am UTC](https://discourse.julialang.org/t/symbolics-not-simplifying-fully/89842 "2022-11-07T06:27:51Z")

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When multiplying expr \* expr^-1 . Symbolics.simplify / Symbolics.simplify\_fractions don’t return 1 julia\> using Symbolics julia\> @variables m mol 2-element Vector{Num}: m mol julia\> simplify(eval(Meta.parse("m^3\*…

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## [Create lower dimensional manifolds in a larger dimension](https://discourse.julialang.org/t/create-lower-dimensional-manifolds-in-a-larger-dimension/89848)

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**Author:** [@JosieG](https://discourse.julialang.org/u/JosieG)\
**Replies:** 0\
**Last updated:** [November 6, 2022, 6:40pm UTC](https://discourse.julialang.org/t/create-lower-dimensional-manifolds-in-a-larger-dimension/89848 "2022-11-06T18:40:52Z")

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I’m very new to Topology. Suppose I want to create a 1-dim/2-dim/3-dim manifold, which is in a 20-dim space, and I will apply some dimension reduction, like PCA to their original dim. Is there anyway to do that? I went t…

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## [Using the same parameter n times in a function call](https://discourse.julialang.org/t/using-the-same-parameter-n-times-in-a-function-call/89833)

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**Author:** [@Zackyzz](https://discourse.julialang.org/u/Zackyzz)\
**Replies:** 7\
**Last updated:** [November 6, 2022, 7:53pm UTC](https://discourse.julialang.org/t/using-the-same-parameter-n-times-in-a-function-call/89833 "2022-11-06T19:53:55Z")

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Hello! I am struggling to find a way to “automate” this type of function call: using LinearAlgebra x = \[rand() rand(); rand() rand()\] kron(x, x) #n=2 kron(x, x, x) #n=3 kron(x, x, x, x) #n=4 Basically, having a 2x2 ma…

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