# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=514

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**Page:** 515

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## [Inequality operator](https://discourse.julialang.org/t/inequality-operator/72232)

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**Author:** [@pjgorski](https://discourse.julialang.org/u/pjgorski)\
**Replies:** 4\
**Last updated:** [November 29, 2021, 2:57pm UTC](https://discourse.julialang.org/t/inequality-operator/72232 "2021-11-29T14:57:15Z")

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Why is there the difference between != and !== operators? Examples: julia\> a = Any\["D", "A", "s", "t"\] julia\> filter(e-\>e!="s",a) 3-element Array{Any,1}: "D" "A" "t" julia\> filter(e-\>e !== "s",a) 4-element Array{Any…

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## [What is the most efficient way of obtaining the orthogonal column space of a matrix?](https://discourse.julialang.org/t/what-is-the-most-efficient-way-of-obtaining-the-orthogonal-column-space-of-a-matrix/72212)

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**Author:** [@Joris\_Pinkse](https://discourse.julialang.org/u/Joris_Pinkse)\
**Replies:** 14\
**Last updated:** [November 29, 2021, 12:36pm UTC](https://discourse.julialang.org/t/what-is-the-most-efficient-way-of-obtaining-the-orthogonal-column-space-of-a-matrix/72212 "2021-11-29T12:36:44Z")

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What is the most efficient way of obtaining the orthogonal column space of a matrix? (many more rows than columns) Q, = svd( X; alg = LinearAlgebra.QRIteration() ) gives me what I want, but is there something more eff…

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## [How to create a parallel task?](https://discourse.julialang.org/t/how-to-create-a-parallel-task/72194)

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**Author:** [@tomhaber](https://discourse.julialang.org/u/tomhaber)\
**Replies:** 8\
**Last updated:** [November 29, 2021, 1:44pm UTC](https://discourse.julialang.org/t/how-to-create-a-parallel-task/72194 "2021-11-29T13:44:08Z")

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I wanted to create a task that runs in parallel with the rest of the code. Seems pretty straightforward, but I’m running into issues I don’t understand. For some reason the sleep in the following code gives an exception,…

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## [Ccall works on global scope but not within function](https://discourse.julialang.org/t/ccall-works-on-global-scope-but-not-within-function/72119)

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**Author:** [@xor0110](https://discourse.julialang.org/u/xor0110)\
**Replies:** 13\
**Last updated:** [November 29, 2021, 12:56pm UTC](https://discourse.julialang.org/t/ccall-works-on-global-scope-but-not-within-function/72119 "2021-11-29T12:56:37Z")

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I’m trying to create bindings to a C library. I generated some Julia code using Clang.jl, and I was able to successfully make some function calls reproducing some C-code program. It’s not very reliable, though. Right now…

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## [Pluto: how to insert a table from LaTeX code into markdown](https://discourse.julialang.org/t/pluto-how-to-insert-a-table-from-latex-code-into-markdown/60481)

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**Author:** [@VivMendes](https://discourse.julialang.org/u/VivMendes)\
**Replies:** 10\
**Last updated:** [November 29, 2021, 9:28am UTC](https://discourse.julialang.org/t/pluto-how-to-insert-a-table-from-latex-code-into-markdown/60481 "2021-11-29T09:28:52Z")

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Pluto is wonderful and I am trying to pass all my slides into Pluto notebooks. A large part of my slides are written in LaTeX and I am struggling with this part in Pluto. For example, I have this table in LaTeX: $$ \\be…

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## [Functions accepting functions and keeping their types](https://discourse.julialang.org/t/functions-accepting-functions-and-keeping-their-types/72044)

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**Author:** [@grjzwaan](https://discourse.julialang.org/u/grjzwaan)\
**Replies:** 11\
**Last updated:** [November 29, 2021, 9:14am UTC](https://discourse.julialang.org/t/functions-accepting-functions-and-keeping-their-types/72044 "2021-11-29T09:14:53Z")

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I’m new to Julia and looking for a good way / advice on passing functions as arguments and keeping the types. My searches did not yield anything that seemed applicable, or at least I understood to be applicable. As a sa…

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## [ForwardDiff error "Cannot determine ordering of Dual tags" when differentiating distributed function with closure](https://discourse.julialang.org/t/forwarddiff-error-cannot-determine-ordering-of-dual-tags-when-differentiating-distributed-function-with-closure/72211)

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**Author:** [@mattwigway](https://discourse.julialang.org/u/mattwigway)\
**Replies:** 1\
**Last updated:** [November 29, 2021, 2:05am UTC](https://discourse.julialang.org/t/forwarddiff-error-cannot-determine-ordering-of-dual-tags-when-differentiating-distributed-function-with-closure/72211 "2021-11-29T02:05:34Z")

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I’m using ForwardDiff to differentiate a function that will be computed across a cluster. When I run the code using a single process everything works fine. However, when I use multiple processes, I get the error Cannot d…

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## [Ping an IP address](https://discourse.julialang.org/t/ping-an-ip-address/72191)

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**Author:** [@\_RBMK](https://discourse.julialang.org/u/_RBMK)\
**Replies:** 5\
**Last updated:** [November 28, 2021, 10:16pm UTC](https://discourse.julialang.org/t/ping-an-ip-address/72191 "2021-11-28T22:16:37Z")

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How about, I’m working on a P2P module for Julia, and I need to do native ping to a host, there is already a post about this in the forum, but I’m trying to do it internally, from Julia. Is it possible to access the Raw …

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## [Why use Julia to build an Earth System Model?](https://discourse.julialang.org/t/why-use-julia-to-build-an-earth-system-model/53180)

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**Author:** [@AlexisRenchon](https://discourse.julialang.org/u/AlexisRenchon)\
**Replies:** 3\
**Last updated:** [November 28, 2021, 8:54pm UTC](https://discourse.julialang.org/t/why-use-julia-to-build-an-earth-system-model/53180 "2021-11-28T20:54:36Z")

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Hi all, Most Earth System Models are written in Fortran, but may be re-written in another language because Fortran has some issues running on GPU based supercomputer. Some consider using C instead, but there are many a…

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## [Strange error when enabling multiple threads](https://discourse.julialang.org/t/strange-error-when-enabling-multiple-threads/72208)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 5\
**Last updated:** [November 28, 2021, 8:22pm UTC](https://discourse.julialang.org/t/strange-error-when-enabling-multiple-threads/72208 "2021-11-28T20:22:40Z")

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I have some code that fails with " ERROR: UndefVarError: T not defined" when I run julia with multiple threads and works fine otherwise. The complete details can be found in https://github.com/invenia/Impute.jl/issues/1…

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## [Inner repeat without allocations](https://discourse.julialang.org/t/inner-repeat-without-allocations/72204)

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**Author:** [@tictaccat](https://discourse.julialang.org/u/tictaccat)\
**Replies:** 3\
**Last updated:** [November 28, 2021, 5:40pm UTC](https://discourse.julialang.org/t/inner-repeat-without-allocations/72204 "2021-11-28T17:40:46Z")

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I want to achieve the effect of the following code: X = randn(1000, 1000) Y = zeros(2000, 2000) Y .= repeat(X, inner=(2,2)) The first two lines are just initialization. I would like the third line to run without alloc…

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## [Failed Process Running a Binary File (solidity compiler)](https://discourse.julialang.org/t/failed-process-running-a-binary-file-solidity-compiler/72170)

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**Author:** [@tlorans](https://discourse.julialang.org/u/tlorans)\
**Replies:** 2\
**Last updated:** [November 28, 2021, 1:16pm UTC](https://discourse.julialang.org/t/failed-process-running-a-binary-file-solidity-compiler/72170 "2021-11-28T13:16:26Z")

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Hello, I’m trying to build a version management tool for the solidity compiler solc in Julia, and, while the process seems to work properly, I’ve got a curious warning message at then end of the process. Here a MWE: u…

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## [\`something\` function is not that much useful with eager args eval, what about a macro one?](https://discourse.julialang.org/t/something-function-is-not-that-much-useful-with-eager-args-eval-what-about-a-macro-one/72188)

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**Author:** [@o314](https://discourse.julialang.org/u/o314)\
**Replies:** 3\
**Last updated:** [November 28, 2021, 6:53am UTC](https://discourse.julialang.org/t/something-function-is-not-that-much-useful-with-eager-args-eval-what-about-a-macro-one/72188 "2021-11-28T06:53:20Z")

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It’s more of an ifelse, since all its args are eagerly evaluated (think & vs &&, and why there is not an and function equivalent to &&). Use on real code™ can lead to significant penalty, if “else clause” args are comput…

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## [NLopt:FORCED\_STOP for vector-valued constraint](https://discourse.julialang.org/t/nlopt-forced-stop-for-vector-valued-constraint/72117)

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**Author:** [@DanielVandH](https://discourse.julialang.org/u/DanielVandH)\
**Replies:** 1\
**Last updated:** [November 27, 2021, 11:00pm UTC](https://discourse.julialang.org/t/nlopt-forced-stop-for-vector-valued-constraint/72117 "2021-11-27T23:00:22Z")

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The following code tries to solve Ax = b subject to x \>= 0 using the NLopt package. using NLopt A = \[0.0372 0.2869; 0.6861 0.7071; 0.6233 0.6245; 0.6344 0.6170\] b = \[0.8587; 0.1781; 0.0747; 0.8405\] function myfunc(x::Ve…

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## [Summing a vector of vectors in a non-allocating way](https://discourse.julialang.org/t/summing-a-vector-of-vectors-in-a-non-allocating-way/72161)

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**Author:** [@jacobusmmsmit](https://discourse.julialang.org/u/jacobusmmsmit)\
**Replies:** 10\
**Last updated:** [November 27, 2021, 7:57pm UTC](https://discourse.julialang.org/t/summing-a-vector-of-vectors-in-a-non-allocating-way/72161 "2021-11-27T19:57:57Z")

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What’s going wrong here, I get a DimensionMismatch error when I run this: input = repeat(\[ones(2)\], 4) output = zeros(2) sum(input) # Gives a 2-element Vector{Float64} sum!(output, input) # Gives a DimensionMismatch err…

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## [How to read gif image files in Julia?](https://discourse.julialang.org/t/how-to-read-gif-image-files-in-julia/72177)

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**Author:** [@sairus7](https://discourse.julialang.org/u/sairus7)\
**Replies:** 1\
**Last updated:** [November 27, 2021, 6:49pm UTC](https://discourse.julialang.org/t/how-to-read-gif-image-files-in-julia/72177 "2021-11-27T18:49:58Z")

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How to read gif image files in Julia?

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## [\[support\] Pytorch for Julia](https://discourse.julialang.org/t/support-pytorch-for-julia/46211)

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**Author:** [@newtojulia](https://discourse.julialang.org/u/newtojulia)\
**Replies:** 10\
**Last updated:** [November 27, 2021, 11:18am UTC](https://discourse.julialang.org/t/support-pytorch-for-julia/46211 "2021-11-27T11:18:27Z")

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Is there any Pytorch framework in Julia.

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## [Sciml\_train with BFGS() (post-training with ADAM)causes following error](https://discourse.julialang.org/t/sciml-train-with-bfgs-post-training-with-adam-causes-following-error/71635)

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**Author:** [@yewalenikhil65](https://discourse.julialang.org/u/yewalenikhil65)\
**Replies:** 6\
**Last updated:** [November 27, 2021, 10:59am UTC](https://discourse.julialang.org/t/sciml-train-with-bfgs-post-training-with-adam-causes-following-error/71635 "2021-11-27T10:59:01Z")

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I am able to minimize the loss using ADAM to some extent… but here is the error i get after I try to reduce it using BFGS(). Any ideas on how to resolve this ? Warning: AD methods failed, using numerical differentiat…

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## [Solving complex differential equation gives MethodError](https://discourse.julialang.org/t/solving-complex-differential-equation-gives-methoderror/72145)

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**Author:** [@DanielVandH](https://discourse.julialang.org/u/DanielVandH)\
**Replies:** 1\
**Last updated:** [November 27, 2021, 10:47am UTC](https://discourse.julialang.org/t/solving-complex-differential-equation-gives-methoderror/72145 "2021-11-27T10:47:56Z")

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The following code tries to solve the complex ODE y’ = (0.3 + it)sin(y)/v with y(-5) = 0.53 + 0.3i. using DifferentialEquations function sysDEUD!(dΦdξ, Φ, p, ξ) ν, x₀ = p η = x₀ + im\*ξ dΦdξ\[1\] = η\*sin(Φ)/ν e…

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## [Simple benchmark for CVS.jl v0.9.11 in Julia 1.6.4](https://discourse.julialang.org/t/simple-benchmark-for-cvs-jl-v0-9-11-in-julia-1-6-4/72140)

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**Author:** [@KZiemian](https://discourse.julialang.org/u/KZiemian)\
**Replies:** 1\
**Last updated:** [November 26, 2021, 11:24pm UTC](https://discourse.julialang.org/t/simple-benchmark-for-cvs-jl-v0-9-11-in-julia-1-6-4/72140 "2021-11-26T23:24:47Z")

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I try to learn some data science in Julia from Julia Academy’s Julia for Data Science and simple benchmark from it is quite surprising for me. I made its code below compact and probably use more packages that it need, ju…

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## [Why is the update of the registries so slow?](https://discourse.julialang.org/t/why-is-the-update-of-the-registries-so-slow/28659)

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**Author:** [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)\
**Replies:** 47\
**Last updated:** [November 26, 2021, 11:12pm UTC](https://discourse.julialang.org/t/why-is-the-update-of-the-registries-so-slow/28659 "2021-11-26T23:12:07Z")

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$ julia \_ \_ \_ \_(\_)\_ | Documentation: https://docs.julialang.org (\_) | (\_) (\_) | \_ \_ \_| |\_ \_\_ \_ | Type "?" for help, "\]?" for Pkg help. | | | | | | |/ \_\` | | | | |\_| | |…

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## [Suppressing text output of display() of Makie](https://discourse.julialang.org/t/suppressing-text-output-of-display-of-makie/72022)

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**Author:** [@wsshin](https://discourse.julialang.org/u/wsshin)\
**Replies:** 5\
**Last updated:** [November 26, 2021, 9:48pm UTC](https://discourse.julialang.org/t/suppressing-text-output-of-display-of-makie/72022 "2021-11-26T21:48:35Z")

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When I create a figure and display it with Makie like the following code: using CairoMakie fig = Figure() ... display(fig) I get a long list of text outputs like this: Scene (800px, 600px): 108 Plots: ├ Combined…

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## [Turing equivalent of Stan/R model from StatisticalRethinking](https://discourse.julialang.org/t/turing-equivalent-of-stan-r-model-from-statisticalrethinking/72092)

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**Author:** [@amit1](https://discourse.julialang.org/u/amit1)\
**Replies:** 5\
**Last updated:** [November 26, 2021, 7:56pm UTC](https://discourse.julialang.org/t/turing-equivalent-of-stan-r-model-from-statisticalrethinking/72092 "2021-11-26T19:56:18Z")

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Consider the following STAN model from Chapter 12 of book Statistical Rethinking library(rethinking) data(UCBadmit) d \<- UCBadmit d$gid \<- ifelse( d$applicant.gender=="male" , 1L , 2L ) dat \<- list( A=d$admit , N=d$appl…

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## [How to use CartesianIndices to replace two nested loops](https://discourse.julialang.org/t/how-to-use-cartesianindices-to-replace-two-nested-loops/72034)

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**Author:** [@Gus\_Hart](https://discourse.julialang.org/u/Gus_Hart)\
**Replies:** 5\
**Last updated:** [November 26, 2021, 6:14pm UTC](https://discourse.julialang.org/t/how-to-use-cartesianindices-to-replace-two-nested-loops/72034 "2021-11-26T18:14:44Z")

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I’m trying to make a scatter plot where the x,y pairs form a (not necessarily rectangular) grid. The color of each point depends in a rather complicated way on the index of the point. Given two vectors, a1 and a2, my poi…

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## [Is there a simple Julia upgrade command?](https://discourse.julialang.org/t/is-there-a-simple-julia-upgrade-command/45691)

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**Author:** [@phymann](https://discourse.julialang.org/u/phymann)\
**Replies:** 47\
**Last updated:** [November 26, 2021, 5:38pm UTC](https://discourse.julialang.org/t/is-there-a-simple-julia-upgrade-command/45691 "2021-11-26T17:38:29Z")

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Hi, can we update Julia just inside Julia by running a command like update, rather than download a new version from website? :smiley:

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## [Generate custom hyperlinks](https://discourse.julialang.org/t/generate-custom-hyperlinks/72127)

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**Author:** [@tencnivel](https://discourse.julialang.org/u/tencnivel)\
**Replies:** 0\
**Last updated:** [November 26, 2021, 4:56pm UTC](https://discourse.julialang.org/t/generate-custom-hyperlinks/72127 "2021-11-26T16:56:34Z")

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Parts of our documentation is generated by calls to julia functions of our home brewed MyDocumentationUtil.jl. This package can for example create a vector of dependencies to other packages, etc… @eval using MyDocument…

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## [Minimum and maximum by column in a datafram](https://discourse.julialang.org/t/minimum-and-maximum-by-column-in-a-datafram/72111)

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**Author:** [@corny85](https://discourse.julialang.org/u/corny85)\
**Replies:** 6\
**Last updated:** [November 26, 2021, 4:03pm UTC](https://discourse.julialang.org/t/minimum-and-maximum-by-column-in-a-datafram/72111 "2021-11-26T16:03:53Z")

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Hello, I’m a beginner with Julia. I’ve got a dataframe called data that i converted in an array of floats. data\_temp = deepcopy(data) array=Matrix(data\_temp\[:,2:size(data\_temp,2)\]) df=Array{Float64}(array) Now, i wan…

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## [Problem with Kaledio and admin rights](https://discourse.julialang.org/t/problem-with-kaledio-and-admin-rights/72110)

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**Author:** [@mottelet](https://discourse.julialang.org/u/mottelet)\
**Replies:** 0\
**Last updated:** [November 26, 2021, 1:24pm UTC](https://discourse.julialang.org/t/problem-with-kaledio-and-admin-rights/72110 "2021-11-26T13:24:18Z")

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Hi, I have made some tests (Julia 1.6.4) with a normal user account under Mac OS and Kaleido does not start,although it starts when the user is admin: julia\> using Plots julia\> plotlyjs() Plots.┌ Warning: Kaleido is n…

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## [Artifacts don't download after instantiating](https://discourse.julialang.org/t/artifacts-dont-download-after-instantiating/72102)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 1\
**Last updated:** [November 26, 2021, 1:04pm UTC](https://discourse.julialang.org/t/artifacts-dont-download-after-instantiating/72102 "2021-11-26T13:04:38Z")

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I don’t understand why an artifact specified in the Artifacts.toml file doesn’t become available after instantiating an environment: shell\> ls Artifacts.toml Manifest.toml Project.toml shell\> cat Artifacts.toml # a s…

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## [How to cut down compile time when inference is not the problem?](https://discourse.julialang.org/t/how-to-cut-down-compile-time-when-inference-is-not-the-problem/59077)

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**Author:** [@fverdugo](https://discourse.julialang.org/u/fverdugo)\
**Replies:** 4\
**Last updated:** [November 26, 2021, 8:13am UTC](https://discourse.julialang.org/t/how-to-cut-down-compile-time-when-inference-is-not-the-problem/59077 "2021-11-26T08:13:33Z")

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Background In Gridap.jl, we have experienced a significant increase in compile times when moving from Julia 1.5 to Julia 1.6. To illustrate this, consider this example: using Gridap function main() domain = (0,1,0,1,…

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