# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1523

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

**Page:** 1524

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## [Using Flux for a neural net solution to differential equations](https://discourse.julialang.org/t/using-flux-for-a-neural-net-solution-to-differential-equations/41996)

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**Author:** [@RuckerC](https://discourse.julialang.org/u/RuckerC)\
**Replies:** 4\
**Last updated:** [January 13, 2021, 4:16pm UTC](https://discourse.julialang.org/t/using-flux-for-a-neural-net-solution-to-differential-equations/41996 "2021-01-13T16:16:12Z")

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I have recently started using Flux to construct a physics informed neural network. To do this, I start with a model u = Chain(Dense(1, 10), Dense(10,15), Dense(15,1)) Then I construct a function to impose the different…

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## [Gradient error in Flux model inputs](https://discourse.julialang.org/t/gradient-error-in-flux-model-inputs/53259)

<div class="topic-metadata">

**Author:** [@Elmo](https://discourse.julialang.org/u/Elmo)\
**Replies:** 5\
**Last updated:** [January 13, 2021, 4:13pm UTC](https://discourse.julialang.org/t/gradient-error-in-flux-model-inputs/53259 "2021-01-13T16:13:54Z")

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Hi all, I am trying to construct a loss function in Flux that is composed of a typical mean squared error component, as well as a derivative component. For some reason I get a Can't differentiate foreigncall expression e…

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## [Error 'No such file or directory'](https://discourse.julialang.org/t/error-no-such-file-or-directory/37168)

<div class="topic-metadata">

**Author:** [@beep](https://discourse.julialang.org/u/beep)\
**Replies:** 11\
**Last updated:** [January 13, 2021, 3:16pm UTC](https://discourse.julialang.org/t/error-no-such-file-or-directory/37168 "2021-01-13T15:16:02Z")

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Hi, This is my very first time using Julia. I tried to add the IJulia package but got this error message: (v1.3) pkg\> add IJulia Cloning default registries into \`C:\\Users\\name\\.julia\` Cloning registry from "https…

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## [Unsatisfiable requirement (Nemo SIUnit Images TexExtensions)](https://discourse.julialang.org/t/unsatisfiable-requirement-nemo-siunit-images-texextensions/22246)

<div class="topic-metadata">

**Author:** [@harven](https://discourse.julialang.org/u/harven)\
**Replies:** 5\
**Last updated:** [January 13, 2021, 1:17pm UTC](https://discourse.julialang.org/t/unsatisfiable-requirement-nemo-siunit-images-texextensions/22246 "2021-01-13T13:17:36Z")

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I installed julia 1.1.0 (linux binary 64bits) together with a few packages (among which Images 0.17.2). I am now trying to install Nemo and I get the following error. julia\> using Pkg; Pkg.add("Nemo") Updating reg…

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## [Flux simple LSTM](https://discourse.julialang.org/t/flux-simple-lstm/51929)

<div class="topic-metadata">

**Author:** [@Tomas\_Berky](https://discourse.julialang.org/u/Tomas_Berky)\
**Replies:** 5\
**Last updated:** [January 13, 2021, 12:56pm UTC](https://discourse.julialang.org/t/flux-simple-lstm/51929 "2021-01-13T12:56:32Z")

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Hello guys, i want to create learn how to create simple LSTM. Do you guys have a guess where can i find some tutorial? Model\_zoo is not sadly not enough for me, i need more commentary on that…

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## [How to find the index of a Dense Axis Array?](https://discourse.julialang.org/t/how-to-find-the-index-of-a-dense-axis-array/53204)

<div class="topic-metadata">

**Author:** [@fredih](https://discourse.julialang.org/u/fredih)\
**Replies:** 3\
**Last updated:** [January 13, 2021, 12:35pm UTC](https://discourse.julialang.org/t/how-to-find-the-index-of-a-dense-axis-array/53204 "2021-01-13T12:35:46Z")

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Hello! I know I can use something like findall(x-\>x==1, myArray) to find the indices of elements of value 1 inside myArray. However, my variables in my optimization problem are DenseAxisArrays, as they are indexed with…

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## [Two Configuration Questions about Julia in VSCode](https://discourse.julialang.org/t/two-configuration-questions-about-julia-in-vscode/52913)

<div class="topic-metadata">

**Author:** [@TI36XPro](https://discourse.julialang.org/u/TI36XPro)\
**Replies:** 4\
**Last updated:** [January 13, 2021, 12:11pm UTC](https://discourse.julialang.org/t/two-configuration-questions-about-julia-in-vscode/52913 "2021-01-13T12:11:04Z")

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Hello, I have two questions regarding Julia and the Julia extension for VS Code. Coming from C++, I know I can use things like tasks.json, c\_cpp\_properties.json, and launch.json to configure my code compilation, its ex…

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## [Collect and type inference](https://discourse.julialang.org/t/collect-and-type-inference/53152)

<div class="topic-metadata">

**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 5\
**Last updated:** [January 13, 2021, 12:00pm UTC](https://discourse.julialang.org/t/collect-and-type-inference/53152 "2021-01-13T12:00:20Z")

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While the type-widening of collect for EltypeUnknown is extremely useful for generic code, my recent experience with a large codebase with time-consuming and occasionally failing inference suggests that these two alterna…

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## [Simple symbolic equation manipulation with ModelingToolkit.jl](https://discourse.julialang.org/t/simple-symbolic-equation-manipulation-with-modelingtoolkit-jl/53130)

<div class="topic-metadata">

**Author:** [@Sciemon](https://discourse.julialang.org/u/Sciemon)\
**Replies:** 2\
**Last updated:** [January 13, 2021, 11:57am UTC](https://discourse.julialang.org/t/simple-symbolic-equation-manipulation-with-modelingtoolkit-jl/53130 "2021-01-13T11:57:55Z")

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I simply would like to isloate a variable from an expression/equation, e.g.: using ModelingToolkit @variables a b c eqs = 0 ~ a + b + c I want to solve this for variable ‘a’ (isolate ‘a’ on the left hand side). As I u…

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## [Plot in even grid layout when the number of subplots is prime (using Plots.jl)](https://discourse.julialang.org/t/plot-in-even-grid-layout-when-the-number-of-subplots-is-prime-using-plots-jl/53206)

<div class="topic-metadata">

**Author:** [@Sh4pe](https://discourse.julialang.org/u/Sh4pe)\
**Replies:** 2\
**Last updated:** [January 13, 2021, 9:40am UTC](https://discourse.julialang.org/t/plot-in-even-grid-layout-when-the-number-of-subplots-is-prime-using-plots-jl/53206 "2021-01-13T09:40:36Z")

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Hi there! I’m using Plots.jl and I’m trying to customize a layout. I want to draw some plots in a grid layout, kind of like they are arranged when I don’t specify a layout at all. Say we have the following situation: l…

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## [Analysis of PkgEval results for upcoming 1.6](https://discourse.julialang.org/t/analysis-of-pkgeval-results-for-upcoming-1-6/53194)

<div class="topic-metadata">

**Author:** [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)\
**Replies:** 4\
**Last updated:** [January 13, 2021, 9:35am UTC](https://discourse.julialang.org/t/analysis-of-pkgeval-results-for-upcoming-1-6/53194 "2021-01-13T09:35:26Z")

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The reason for this post is to describe the way PkgEval is used for new Julia releases and some analysis of the failures for the upcoming 1.6 release. As always, when preparing for a new release, we run something called…

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## [Question on LaTeX in Axis Labels in Pluto with Plots.jl](https://discourse.julialang.org/t/question-on-latex-in-axis-labels-in-pluto-with-plots-jl/53268)

<div class="topic-metadata">

**Author:** [@TI36XPro](https://discourse.julialang.org/u/TI36XPro)\
**Replies:** 0\
**Last updated:** [January 13, 2021, 4:30am UTC](https://discourse.julialang.org/t/question-on-latex-in-axis-labels-in-pluto-with-plots-jl/53268 "2021-01-13T04:30:11Z")

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Hello, I’m watching this video here in which a plot has been created in a Pluto notebook and which appears to be the GR backend. I’ve tried to reproduce it but I can’t get my text to be superscripts and keep the origina…

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## [How to convert string column of dataframe to float with missing values?](https://discourse.julialang.org/t/how-to-convert-string-column-of-dataframe-to-float-with-missing-values/53261)

<div class="topic-metadata">

**Author:** [@mocalvao](https://discourse.julialang.org/u/mocalvao)\
**Replies:** 2\
**Last updated:** [January 12, 2021, 11:14pm UTC](https://discourse.julialang.org/t/how-to-convert-string-column-of-dataframe-to-float-with-missing-values/53261 "2021-01-12T23:14:13Z")

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I have a (very simplified below) xlsx file like: Start | End | Q1 | Q2 | Q3 10 Jan 2021 15:00 | 10 Jan 2021 17:00 | 5.50 | 2.70 | - 10 Jan 2021 15:03 | 10 Jan 2021 16:53 | 2.70 | 3.00 | 1.5…

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## [How to print name of parametric type without, uhm, parameters?](https://discourse.julialang.org/t/how-to-print-name-of-parametric-type-without-uhm-parameters/53248)

<div class="topic-metadata">

**Author:** [@DrChainsaw](https://discourse.julialang.org/u/DrChainsaw)\
**Replies:** 5\
**Last updated:** [January 12, 2021, 10:41pm UTC](https://discourse.julialang.org/t/how-to-print-name-of-parametric-type-without-uhm-parameters/53248 "2021-01-12T22:41:02Z")

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For example: julia\> struct A{T} a::T end julia\> simpletypename1(x::F) where F = string(F); julia\> @assert simpletypename1(A(3)) === "A" # Fails, as type is A{Int64} julia\> simpletypename2(x::F) where F…

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## [Move a plane with slider in Makie.jl](https://discourse.julialang.org/t/move-a-plane-with-slider-in-makie-jl/53258)

<div class="topic-metadata">

**Author:** [@Flausi](https://discourse.julialang.org/u/Flausi)\
**Replies:** 0\
**Last updated:** [January 12, 2021, 10:06pm UTC](https://discourse.julialang.org/t/move-a-plane-with-slider-in-makie-jl/53258 "2021-01-12T22:06:53Z")

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Hello, I tried to use Makie.jl to move a layer in a spatial plot via a slider and update the data depending on how the slider is set. This actually works quite well, but the layer is not moved with the ‘transformation -…

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## [Large ODE System Solving using @threads Crashes with Different Thread Counts](https://discourse.julialang.org/t/large-ode-system-solving-using-threads-crashes-with-different-thread-counts/50398)

<div class="topic-metadata">

**Author:** [@Jack\_hues](https://discourse.julialang.org/u/Jack_hues)\
**Replies:** 8\
**Last updated:** [January 12, 2021, 10:05pm UTC](https://discourse.julialang.org/t/large-ode-system-solving-using-threads-crashes-with-different-thread-counts/50398 "2021-01-12T22:05:37Z")

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Hi, I’m currently working on solving a discretized PDE-ODE coupled system, which has been discretized into a system of odes where we then a noise in the form of a stochastic process, converting the ODE system into a sys…

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## [Julia recompiling unchanged modules](https://discourse.julialang.org/t/julia-recompiling-unchanged-modules/53252)

<div class="topic-metadata">

**Author:** [@bluesmoon](https://discourse.julialang.org/u/bluesmoon)\
**Replies:** 5\
**Last updated:** [January 12, 2021, 9:59pm UTC](https://discourse.julialang.org/t/julia-recompiling-unchanged-modules/53252 "2021-01-12T21:59:05Z")

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Hi all, I’m using julia 1.5.3 on Ubuntu. I have a bunch of modules with dependencies, and a one line script that just has a using statement for these modules (no other code in the script). I first precompile all my mo…

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## [How to deal with recursive type dependencies in immutable structs?](https://discourse.julialang.org/t/how-to-deal-with-recursive-type-dependencies-in-immutable-structs/53173)

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**Author:** [@jeffreyesun](https://discourse.julialang.org/u/jeffreyesun)\
**Replies:** 5\
**Last updated:** [January 12, 2021, 9:52pm UTC](https://discourse.julialang.org/t/how-to-deal-with-recursive-type-dependencies-in-immutable-structs/53173 "2021-01-12T21:52:42Z")

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I want to define structs with a parent-child relationship: struct Parent children::Vector{Child} end struct Child parent::Parent end When I try to execute these definitions, I get: ERROR: UnDefVarError: Child…

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## [Performance differences of contiguous vs non-contiguous column indexing?](https://discourse.julialang.org/t/performance-differences-of-contiguous-vs-non-contiguous-column-indexing/53243)

<div class="topic-metadata">

**Author:** [@mkarikom](https://discourse.julialang.org/u/mkarikom)\
**Replies:** 2\
**Last updated:** [January 12, 2021, 9:23pm UTC](https://discourse.julialang.org/t/performance-differences-of-contiguous-vs-non-contiguous-column-indexing/53243 "2021-01-12T21:23:38Z")

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A quick test shows a 15% decrease in mean run time for the non-contiguous case, which seems huge. Why would this happen? using Random,BenchmarkTools,LinearAlgebra rng = MersenneTwister(1234); # data a = rand(rng,1000,…

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## [Explicit distribution of chunks in SharedArray?](https://discourse.julialang.org/t/explicit-distribution-of-chunks-in-sharedarray/53249)

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**Author:** [@mkarikom](https://discourse.julialang.org/u/mkarikom)\
**Replies:** 2\
**Last updated:** [January 12, 2021, 8:23pm UTC](https://discourse.julialang.org/t/explicit-distribution-of-chunks-in-sharedarray/53249 "2021-01-12T20:23:24Z")

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How can I construct a SharedArray with a specific chunk distribution across workers? For instance: julia -p 2 using SharedArrays,Distributed,Test @everywhere using SharedArrays a = SharedArray{Float64,2}((3,5),init = …

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## [Take gradient of parameters not working](https://discourse.julialang.org/t/take-gradient-of-parameters-not-working/53250)

<div class="topic-metadata">

**Author:** [@Elmo](https://discourse.julialang.org/u/Elmo)\
**Replies:** 0\
**Last updated:** [January 12, 2021, 8:20pm UTC](https://discourse.julialang.org/t/take-gradient-of-parameters-not-working/53250 "2021-01-12T20:20:58Z")

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Hi all! I am trying to construct a loss function in Flux (v0.11.2) that regularizes the parameters relative to some number (not 0). Below is a minimal working example, does anybody know why the gradients are nothing? us…

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## [ArchGDAL.jl compile error using Julia1.6](https://discourse.julialang.org/t/archgdal-jl-compile-error-using-julia1-6/53238)

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**Author:** [@zhangliye](https://discourse.julialang.org/u/zhangliye)\
**Replies:** 1\
**Last updated:** [January 12, 2021, 7:59pm UTC](https://discourse.julialang.org/t/archgdal-jl-compile-error-using-julia1-6/53238 "2021-01-12T19:59:20Z")

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I got the following error when run using ArchGDAL with Julia1.6. There is no problem with Julia1.5. The error is as following. Julia Version 1.6.0-beta1 Commit b84990e1ac (2021-01-08 12:42 UTC) Platform Info: OS: mac…

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## [Application Code Organization](https://discourse.julialang.org/t/application-code-organization/53224)

<div class="topic-metadata">

**Author:** [@Nathan\_Boyer](https://discourse.julialang.org/u/Nathan_Boyer)\
**Replies:** 17\
**Last updated:** [January 12, 2021, 7:25pm UTC](https://discourse.julialang.org/t/application-code-organization/53224 "2021-01-12T19:25:22Z")

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Goal I am developing what I think would be called an application. It is meant for a novice end user that can just change some inputs and then run. It will compute some quantities and then generate a report with text and…

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## [UndefVarError with list comprehensions, but not with for...end](https://discourse.julialang.org/t/undefvarerror-with-list-comprehensions-but-not-with-for-end/53237)

<div class="topic-metadata">

**Author:** [@hdavid16](https://discourse.julialang.org/u/hdavid16)\
**Replies:** 5\
**Last updated:** [January 12, 2021, 7:23pm UTC](https://discourse.julialang.org/t/undefvarerror-with-list-comprehensions-but-not-with-for-end/53237 "2021-01-12T19:23:13Z")

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It would be nice to be able to do the following without the UndefVarError: julia\> reduce(+, 1 for i in 1:2, j in i:3; init = 0) ERROR: UndefVarError: i not defined Stacktrace: \[1\] top-level scope at none:1 julia\> sum(…

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## [Multithreading](https://discourse.julialang.org/t/multithreading/53050)

<div class="topic-metadata">

**Author:** [@Laco\_Kovac](https://discourse.julialang.org/u/Laco_Kovac)\
**Replies:** 4\
**Last updated:** [January 12, 2021, 7:00pm UTC](https://discourse.julialang.org/t/multithreading/53050 "2021-01-12T19:00:27Z")

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I have 3/several functions taking some parameter(s) and returning Bool. Behind each of them is SQL Query. Currently I am running them sychronously, one after another, and if one of them returns false, I don’t need to c…

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## [Mapping all methods of a module into a Dictionary](https://discourse.julialang.org/t/mapping-all-methods-of-a-module-into-a-dictionary/53179)

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**Author:** [@djholiver](https://discourse.julialang.org/u/djholiver)\
**Replies:** 7\
**Last updated:** [January 12, 2021, 6:20pm UTC](https://discourse.julialang.org/t/mapping-all-methods-of-a-module-into-a-dictionary/53179 "2021-01-12T18:20:39Z")

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Hi, I’m trying to populate a Dictionary{String, Function} with the exported methods found in StatsBase so that I can expose them to a UI and I’m getting unexpected results: using StatsBase d = Dict{String,Function}() …

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## [Help with bottleneck in dynamic programming](https://discourse.julialang.org/t/help-with-bottleneck-in-dynamic-programming/53066)

<div class="topic-metadata">

**Author:** [@jmatheusgpa](https://discourse.julialang.org/u/jmatheusgpa)\
**Replies:** 4\
**Last updated:** [January 12, 2021, 6:14pm UTC](https://discourse.julialang.org/t/help-with-bottleneck-in-dynamic-programming/53066 "2021-01-12T18:14:14Z")

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My goal is to calculate all the possible outcomes in a finite dynamic programming problem. The grid size is 100, there are three state variables and T periods. A bottleneck is the following function, which I’ve started …

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## [SingularSpectrumAnalysis and CPU load](https://discourse.julialang.org/t/singularspectrumanalysis-and-cpu-load/53212)

<div class="topic-metadata">

**Author:** [@Colin\_Beckingham](https://discourse.julialang.org/u/Colin_Beckingham)\
**Replies:** 3\
**Last updated:** [January 12, 2021, 6:09pm UTC](https://discourse.julialang.org/t/singularspectrumanalysis-and-cpu-load/53212 "2021-01-12T18:09:21Z")

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SSA does a good job of extracting trend and seasonality from a time series. However widening the window on a large dataset puts quite a load on my CPU (GPU is too old to contribute to calculation in Julia) heats up my CP…

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## [Resolving package versions... when adding Makie](https://discourse.julialang.org/t/resolving-package-versions-when-adding-makie/53139)

<div class="topic-metadata">

**Author:** [@elkinjosuerc](https://discourse.julialang.org/u/elkinjosuerc)\
**Replies:** 1\
**Last updated:** [January 12, 2021, 6:04pm UTC](https://discourse.julialang.org/t/resolving-package-versions-when-adding-makie/53139 "2021-01-12T18:04:57Z")

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Hi everyone!!! when i try to import Pkg Pkg.add(“Makie”) It shows me this error, may anyone helpme with this? Resolving package versions… Unsatisfiable requirements detected for package PlotUtils \[995b91a9\]: PlotUt…

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## [How to make Date objects in "mm-dd-yyyy" format?](https://discourse.julialang.org/t/how-to-make-date-objects-in-mm-dd-yyyy-format/53175)

<div class="topic-metadata">

**Author:** [@Michael\_Barmann](https://discourse.julialang.org/u/Michael_Barmann)\
**Replies:** 2\
**Last updated:** [January 12, 2021, 5:27pm UTC](https://discourse.julialang.org/t/how-to-make-date-objects-in-mm-dd-yyyy-format/53175 "2021-01-12T17:27:00Z")

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I’m trying to create some Dates which I want to display in “mm-dd-yyyy” format. The documentation (https://docs.julialang.org/en/v1/stdlib/Dates/#Constructors) only seems to give examples where the dates are in “yyyy-mm-…

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