# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1658

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

**Page:** 1659

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## [Why are tuples covariant?](https://discourse.julialang.org/t/why-are-tuples-covariant/45005)

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**Author:** [@OliverEvans96](https://discourse.julialang.org/u/OliverEvans96)\
**Replies:** 2\
**Last updated:** [August 15, 2020, 6:17pm UTC](https://discourse.julialang.org/t/why-are-tuples-covariant/45005 "2020-08-15T18:17:14Z")

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The manual section on Parametric Types says that Julia’s type parameters are invariant but the section on Tuple Types says Tuple types are covariant in their parameters I’m just curious about the reason behind…

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## [Why is BLAS dot product so much faster than Julia loop?](https://discourse.julialang.org/t/why-is-blas-dot-product-so-much-faster-than-julia-loop/44994)

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**Author:** [@JeffFessler](https://discourse.julialang.org/u/JeffFessler)\
**Replies:** 18\
**Last updated:** [August 15, 2020, 4:48pm UTC](https://discourse.julialang.org/t/why-is-blas-dot-product-so-much-faster-than-julia-loop/44994 "2020-08-15T16:48:19Z")

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I wanted to illustrate the beauty of Julia for my class by showing the speed of a simple vector dot product, but to my surprise the Julia loop version was about 5x slower than the built-in dot() that (I think) calls BLAS…

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## [Problems to build PyCall](https://discourse.julialang.org/t/problems-to-build-pycall/44995)

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**Author:** [@angeloaliano1](https://discourse.julialang.org/u/angeloaliano1)\
**Replies:** 1\
**Last updated:** [August 15, 2020, 4:37pm UTC](https://discourse.julialang.org/t/problems-to-build-pycall/44995 "2020-08-15T16:37:50Z")

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Dear all, I am with serious problem. I cannot to build the package PyCall to use the Package SymPy. I am with Julia 1.5, recently installed. I have run: Pkg.add(“PyCall”) import Pkg; Pkg.add(“Conda”) Pkg.build(“PyC…

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## [Is it possible to run a cleanup code after a jldoctest block has been evaluated?](https://discourse.julialang.org/t/is-it-possible-to-run-a-cleanup-code-after-a-jldoctest-block-has-been-evaluated/44999)

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**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 0\
**Last updated:** [August 15, 2020, 4:31pm UTC](https://discourse.julialang.org/t/is-it-possible-to-run-a-cleanup-code-after-a-jldoctest-block-has-been-evaluated/44999 "2020-08-15T16:31:33Z")

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Documenter allows the inclusion of setup codes for a jldoctest section. Is there something analogous that may be run once a block has finished running, sort of a clean-up code? For example, I’m looking for something lik…

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## [BenchmarkTools Puzzles](https://discourse.julialang.org/t/benchmarktools-puzzles/44993)

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**Author:** [@Hawk](https://discourse.julialang.org/u/Hawk)\
**Replies:** 0\
**Last updated:** [August 15, 2020, 1:52pm UTC](https://discourse.julialang.org/t/benchmarktools-puzzles/44993 "2020-08-15T13:52:56Z")

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I am following Chris’s tutorial of mit18337 course, in his lecture note(Optimizing Serial Code), there is an example about evaluating cost of heap allocation. using LinearAlgebra, BenchmarkTools function alloc\_timer(n) …

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## [Is it possible for Julia to print numeric output in the REPL with underscores as digit separators?](https://discourse.julialang.org/t/is-it-possible-for-julia-to-print-numeric-output-in-the-repl-with-underscores-as-digit-separators/44962)

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**Author:** [@philip](https://discourse.julialang.org/u/philip)\
**Replies:** 15\
**Last updated:** [August 15, 2020, 12:38pm UTC](https://discourse.julialang.org/t/is-it-possible-for-julia-to-print-numeric-output-in-the-repl-with-underscores-as-digit-separators/44962 "2020-08-15T12:38:59Z")

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Say I need to compute the size of a cross join before attempting it. My eyes aren’t great. julia\> 1\_000\*144\*30\*20\*15\*18 23328000000 Wait, how many 0s are there? julia\> ans==2\_332\_800\_000 false Urgh. Can I just see …

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## [How to fiil gaps in the multiple Satellite Images?](https://discourse.julialang.org/t/how-to-fiil-gaps-in-the-multiple-satellite-images/44408)

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**Author:** [@hafez\_ahmad](https://discourse.julialang.org/u/hafez_ahmad)\
**Replies:** 2\
**Last updated:** [August 15, 2020, 9:40am UTC](https://discourse.julialang.org/t/how-to-fiil-gaps-in-the-multiple-satellite-images/44408 "2020-08-15T09:40:53Z")

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I have download 200 Landsat7 satellite images. all images have data gaps. I can solve this problem by using ArcGIS commercial software. however, this process is so time consuming and boring. is there any fast way using …

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## [How to concatenate multiple \`.gz\` files within Julia?](https://discourse.julialang.org/t/how-to-concatenate-multiple-gz-files-within-julia/44975)

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**Author:** [@biona001](https://discourse.julialang.org/u/biona001)\
**Replies:** 2\
**Last updated:** [August 15, 2020, 8:18am UTC](https://discourse.julialang.org/t/how-to-concatenate-multiple-gz-files-within-julia/44975 "2020-08-15T08:18:26Z")

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I want to combine multiple .gz files into 1 within Julia. The command to do so in the command line is: cat file1.gz file2.gz file3.gz \> allfiles.gz But the following does not work: files = \["file1.gz", "file2.gz", "fi…

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## [Model Many to Many relationships](https://discourse.julialang.org/t/model-many-to-many-relationships/44967)

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**Author:** [@Alec\_Loudenback](https://discourse.julialang.org/u/Alec_Loudenback)\
**Replies:** 3\
**Last updated:** [August 15, 2020, 3:12am UTC](https://discourse.julialang.org/t/model-many-to-many-relationships/44967 "2020-08-15T03:12:48Z")

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If I have a many-to-many set of relationships that I want to model, what are performant and pleasant ways to do this? E.g. As can have many Bs, and different As have a relationship with the same B: struct A conten…

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## [Adding a trendline or line of best fit](https://discourse.julialang.org/t/adding-a-trendline-or-line-of-best-fit/44939)

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**Author:** [@HelgavonLichtenstein](https://discourse.julialang.org/u/HelgavonLichtenstein)\
**Replies:** 7\
**Last updated:** [August 15, 2020, 1:12am UTC](https://discourse.julialang.org/t/adding-a-trendline-or-line-of-best-fit/44939 "2020-08-15T01:12:57Z")

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I’m quite surprised there are no posts about trendlines or lines of best fit on these forums. Maybe they are called something else? The only thing I’ve been able to find online is this: using LinearAlgebra dates = 1:150…

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## [Bin behaviour in fit( Histogram, (x,y) ) |\> Plots.heatmap](https://discourse.julialang.org/t/bin-behaviour-in-fit-histogram-x-y-plots-heatmap/44963)

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**Author:** [@VMHidalgo](https://discourse.julialang.org/u/VMHidalgo)\
**Replies:** 2\
**Last updated:** [August 15, 2020, 1:10am UTC](https://discourse.julialang.org/t/bin-behaviour-in-fit-histogram-x-y-plots-heatmap/44963 "2020-08-15T01:10:55Z")

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Hi, I would to ask for your support with this one. I am fitting an 2d-histrogram to a tuple of vectors. Then, I try to heatmap it but I cannot make it work. Interestingly, for random data it works as it should. I canno…

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## [Display values from Distributions](https://discourse.julialang.org/t/display-values-from-distributions/44971)

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**Author:** [@sriharitn](https://discourse.julialang.org/u/sriharitn)\
**Replies:** 5\
**Last updated:** [August 15, 2020, 1:00am UTC](https://discourse.julialang.org/t/display-values-from-distributions/44971 "2020-08-15T01:00:01Z")

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I’m trying to assign values of Beta(a,b) function in Distributions package to x but the value is not printing in console. using Distributions x = Beta(1,2) Gives me julia\> x Beta{Float64}(α=1.0, β=2.0) How can I assi…

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## [Installation Issues for IAI](https://discourse.julialang.org/t/installation-issues-for-iai/34764)

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**Author:** [@adewald](https://discourse.julialang.org/u/adewald)\
**Replies:** 1\
**Last updated:** [August 14, 2020, 10:17pm UTC](https://discourse.julialang.org/t/installation-issues-for-iai/34764 "2020-08-14T22:17:41Z")

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Hi I am new to Julia and I keep getting an error when I try to run the code below to import julia and iai from interpretableai: from julia import Julia Julia(compiled\_modules=False,runtime=“/Applications/Julia-1.3.app/…

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## [Passing a function to an eval in my module](https://discourse.julialang.org/t/passing-a-function-to-an-eval-in-my-module/44955)

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**Author:** [@koosp](https://discourse.julialang.org/u/koosp)\
**Replies:** 4\
**Last updated:** [August 14, 2020, 10:11pm UTC](https://discourse.julialang.org/t/passing-a-function-to-an-eval-in-my-module/44955 "2020-08-14T22:11:08Z")

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I made a module which had a function, that calls another function inside of it to compute partial derivatives. I tested it with Base functions like exp, sin and so on and it worked, it still works. I also tested it with …

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## [The Julia Language on Twitch](https://discourse.julialang.org/t/the-julia-language-on-twitch/44958)

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**Author:** [@logankilpatrick](https://discourse.julialang.org/u/logankilpatrick)\
**Replies:** 2\
**Last updated:** [August 14, 2020, 9:56pm UTC](https://discourse.julialang.org/t/the-julia-language-on-twitch/44958 "2020-08-14T21:56:33Z")

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Hey all, if you use Twitch or have an account, please consider following us there: Twitch We are trying to help build the #JuliaLang streamer community. Also check out https://JuliaLang.live for the official streaming …

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## [Grassmann.jl A\\b 3x faster than Julia's StaticArrays.jl](https://discourse.julialang.org/t/grassmann-jl-a-b-3x-faster-than-julias-staticarrays-jl/41451)

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**Author:** [@chakravala](https://discourse.julialang.org/u/chakravala)\
**Replies:** 34\
**Last updated:** [August 14, 2020, 8:13pm UTC](https://discourse.julialang.org/t/grassmann-jl-a-b-3x-faster-than-julias-staticarrays-jl/41451 "2020-08-14T20:13:03Z")

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In this algebra, it’s possible to compute on a mesh of arbitrary 5 dimensional conformal geometric algebra simplices, which can be represented by a bundle of nested dyadic tensors. julia\> using Grassmann, StaticArrays;…

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## [Inverse and backslash \\ division](https://discourse.julialang.org/t/inverse-and-backslash-division/44680)

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**Author:** [@luboshanus](https://discourse.julialang.org/u/luboshanus)\
**Replies:** 5\
**Last updated:** [August 14, 2020, 8:18pm UTC](https://discourse.julialang.org/t/inverse-and-backslash-division/44680 "2020-08-14T20:18:06Z")

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Hi, could anyone please explain to me how to use inv() and \\ properly to have valid results. Alse when checking with GLM package basic OLS gives different results and sometimes it is way too far. It might be caused by t…

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## [Multithreading not giving noticeable advantage when running parallel functions](https://discourse.julialang.org/t/multithreading-not-giving-noticeable-advantage-when-running-parallel-functions/44830)

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**Author:** [@Torkel](https://discourse.julialang.org/u/Torkel)\
**Replies:** 19\
**Last updated:** [August 14, 2020, 8:11pm UTC](https://discourse.julialang.org/t/multithreading-not-giving-noticeable-advantage-when-running-parallel-functions/44830 "2020-08-14T20:11:55Z")

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Hello, I have a research problem where I try to determine how a system’s behaviour depends on parameter values. Essentially I have a function determine\_behaviour(p) which takes a set of parameter values and determines h…

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## [User-defined vector input function in JuMP 0.18.6](https://discourse.julialang.org/t/user-defined-vector-input-function-in-jump-0-18-6/44956)

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**Author:** [@Ken\_Lin](https://discourse.julialang.org/u/Ken_Lin)\
**Replies:** 0\
**Last updated:** [August 14, 2020, 7:56pm UTC](https://discourse.julialang.org/t/user-defined-vector-input-function-in-jump-0-18-6/44956 "2020-08-14T19:56:51Z")

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Is it possible to have user-defined functions with vector input in JuMP 0.18.6? Or is there a way to do similar things? I would like to use the NLopt solver (GitHub - JuliaOpt/NLopt.jl: Package to call the NLopt nonlinea…

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## [Accessing an element of a structure based off of a string](https://discourse.julialang.org/t/accessing-an-element-of-a-structure-based-off-of-a-string/44952)

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**Author:** [@smickus](https://discourse.julialang.org/u/smickus)\
**Replies:** 6\
**Last updated:** [August 14, 2020, 7:57pm UTC](https://discourse.julialang.org/t/accessing-an-element-of-a-structure-based-off-of-a-string/44952 "2020-08-14T19:57:07Z")

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I want to be able to access and change an element of a structure based off a string that has been read in from a text file and then change the value of that element. The element that is being changed could of several d…

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## [Error when using dynamic parallelism with six or more arguments](https://discourse.julialang.org/t/error-when-using-dynamic-parallelism-with-six-or-more-arguments/44931)

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**Author:** [@emiwar](https://discourse.julialang.org/u/emiwar)\
**Replies:** 1\
**Last updated:** [August 14, 2020, 7:50pm UTC](https://discourse.julialang.org/t/error-when-using-dynamic-parallelism-with-six-or-more-arguments/44931 "2020-08-14T19:50:34Z")

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Hi, I’m getting an error (unsupported dynamic function invocation) when I run manyArgs(a, b, c, d, e, f) = nothing caller() = (@CUDA.cuda dynamic=true manyArgs(1,2,3,4,5,6); nothing) @CUDA.cuda caller() while manyArg…

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## [Suggestions for very quiet keyboard](https://discourse.julialang.org/t/suggestions-for-very-quiet-keyboard/44609)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 34\
**Last updated:** [August 14, 2020, 7:35pm UTC](https://discourse.julialang.org/t/suggestions-for-very-quiet-keyboard/44609 "2020-08-14T19:35:28Z")

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Now that working from home is becoming the new normal, I would like to minimize the noise impact of late night coding on others. I am currently using a Dell KB216 which is am satisfied with when it comes to typing and f…

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## [Update one, and only one package](https://discourse.julialang.org/t/update-one-and-only-one-package/33755)

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**Author:** [@cstjean](https://discourse.julialang.org/u/cstjean)\
**Replies:** 3\
**Last updated:** [August 14, 2020, 6:58pm UTC](https://discourse.julialang.org/t/update-one-and-only-one-package/33755 "2020-08-14T18:58:53Z")

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I’ve got some Julia application that was released, neatly instantiable from its MANIFEST file. Say it has versions v1.0.0, v1.1.0 and v2.0.0. There was a bug in 1.1.0, that was released 5 months ago. It was some issue wi…

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## [Use of getindex.(L,1) in a for loop](https://discourse.julialang.org/t/use-of-getindex-l-1-in-a-for-loop/44940)

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**Author:** [@juliamatt](https://discourse.julialang.org/u/juliamatt)\
**Replies:** 2\
**Last updated:** [August 14, 2020, 4:18pm UTC](https://discourse.julialang.org/t/use-of-getindex-l-1-in-a-for-loop/44940 "2020-08-14T16:18:31Z")

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I am converting some old Julia 0.5 code into Matlab. I know broadcasting uses the dot notation but I don’t understand why you would want to use: L = getindex.(L,1) inside a for or while loop in Julia code. At the com…

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## [How can I run hooks before and after the execution of a command in the REPL?](https://discourse.julialang.org/t/how-can-i-run-hooks-before-and-after-the-execution-of-a-command-in-the-repl/44815)

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**Author:** [@NightMachinary](https://discourse.julialang.org/u/NightMachinary)\
**Replies:** 11\
**Last updated:** [August 14, 2020, 3:54pm UTC](https://discourse.julialang.org/t/how-can-i-run-hooks-before-and-after-the-execution-of-a-command-in-the-repl/44815 "2020-08-14T15:54:13Z")

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I first opened an issue on VSCode’s Julia extension to make a bell sound after a long-running command. After more thought, I reached the conclusion that having hooks that run arbitrary Julia code before and after command…

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## [Maintaining custom package forks](https://discourse.julialang.org/t/maintaining-custom-package-forks/44885)

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**Author:** [@tbeason](https://discourse.julialang.org/u/tbeason)\
**Replies:** 4\
**Last updated:** [August 14, 2020, 3:30pm UTC](https://discourse.julialang.org/t/maintaining-custom-package-forks/44885 "2020-08-14T15:30:32Z")

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There have been multiple times now where I have considered maintaining my own fork of a registered package. But, I’m wondering if there are any tools that might make it easier to do so, and if anybody else is doing anyth…

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## [Please support updated Julia version on repl.it](https://discourse.julialang.org/t/please-support-updated-julia-version-on-repl-it/44890)

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**Author:** [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)\
**Replies:** 6\
**Last updated:** [August 14, 2020, 2:48pm UTC](https://discourse.julialang.org/t/please-support-updated-julia-version-on-repl-it/44890 "2020-08-14T14:48:06Z")

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https://repl.it/language-requests/p/please-install-up-to-date-julia

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## [Add line style to legend](https://discourse.julialang.org/t/add-line-style-to-legend/44667)

<div class="topic-metadata">

**Author:** [@HelgavonLichtenstein](https://discourse.julialang.org/u/HelgavonLichtenstein)\
**Replies:** 3\
**Last updated:** [August 14, 2020, 1:45pm UTC](https://discourse.julialang.org/t/add-line-style-to-legend/44667 "2020-08-14T13:45:48Z")

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Is there a way to add something (in this case a line style) to a legend without plotting it? I am using Plot.jl MWE aa = 1:10 bb = 10 .\* rand(10) cc = 10 .\* rand(10) dd = 10 .\* rand(10) ee = 10 .\* rand(10) ff = 10 .\* r…

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## [The logarithm of a tensor](https://discourse.julialang.org/t/the-logarithm-of-a-tensor/44849)

<div class="topic-metadata">

**Author:** [@F-YF](https://discourse.julialang.org/u/F-YF)\
**Replies:** 10\
**Last updated:** [August 14, 2020, 1:25pm UTC](https://discourse.julialang.org/t/the-logarithm-of-a-tensor/44849 "2020-08-14T13:25:49Z")

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I want to take the logarithm of a tensor, what do I do

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## [How to define a formula with a vector of string names for GLM.jl?](https://discourse.julialang.org/t/how-to-define-a-formula-with-a-vector-of-string-names-for-glm-jl/44930)

<div class="topic-metadata">

**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 3\
**Last updated:** [August 14, 2020, 1:20pm UTC](https://discourse.julialang.org/t/how-to-define-a-formula-with-a-vector-of-string-names-for-glm-jl/44930 "2020-08-14T13:20:11Z")

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I got a DataFrame that I wanted to fit a GLM model with but I would like to be able to build a formula (with hundreds of variables) programmatically without having to write it out by hand. So the best I can think of is v…

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