# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1906

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

**Page:** 1907

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## [Makie: Draw two meshes in one scene: Struggling with positioning](https://discourse.julialang.org/t/makie-draw-two-meshes-in-one-scene-struggling-with-positioning/29651)

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**Author:** [@zsoerenm](https://discourse.julialang.org/u/zsoerenm)\
**Replies:** 1\
**Last updated:** [October 8, 2019, 12:43pm UTC](https://discourse.julialang.org/t/makie-draw-two-meshes-in-one-scene-struggling-with-positioning/29651 "2019-10-08T12:43:37Z")

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I tried to draw two boxes in one scene. Both should be centered, but it appears, that there is something else going on: using Makie scene = mesh(Rect3D(((1,1,0), (-1,-1,0.1))), color = "green") mesh!(scene, Rect3D(((.25…

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## [Julia v1.3.0-rc3 is now available](https://discourse.julialang.org/t/julia-v1-3-0-rc3-is-now-available/29471)

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**Author:** [@ararslan](https://discourse.julialang.org/u/ararslan)\
**Replies:** 2\
**Last updated:** [October 8, 2019, 12:06pm UTC](https://discourse.julialang.org/t/julia-v1-3-0-rc3-is-now-available/29471 "2019-10-08T12:06:49Z")

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The third (and we hope final) release candidate for Julia v1.3.0 is now available. Get binaries for all of your favorite platforms at Download Julia, assuming of course that your favorite platforms are Linux (i686, x86-6…

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## [Creating a new package](https://discourse.julialang.org/t/creating-a-new-package/29400)

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**Author:** [@marouane](https://discourse.julialang.org/u/marouane)\
**Replies:** 7\
**Last updated:** [October 8, 2019, 10:13am UTC](https://discourse.julialang.org/t/creating-a-new-package/29400 "2019-10-08T10:13:27Z")

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i’ve created a new package named QuantumRelay, and i’m putting all the files that i need for this package in one file and everything and i’ve added also all the dependencies needed and when i’m typing using QuantumRelay …

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## [AM/PM in Date Format](https://discourse.julialang.org/t/am-pm-in-date-format/17356)

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**Author:** [@MLackner](https://discourse.julialang.org/u/MLackner)\
**Replies:** 3\
**Last updated:** [October 8, 2019, 8:00am UTC](https://discourse.julialang.org/t/am-pm-in-date-format/17356 "2019-10-08T08:00:29Z")

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Hi! How do I get the am/pm information from a string to a DateTime? I’ve got the following string: str = "11/7/2018 1:22:51 PM" and want to parse it as a DateTime: DateTime(str, dateformat"m/d/yyyy H:mm:ss ?") Whic…

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## [How to represent binary array (slot occupied = 1, slot open = 0) in the form of colored squares](https://discourse.julialang.org/t/how-to-represent-binary-array-slot-occupied-1-slot-open-0-in-the-form-of-colored-squares/29631)

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**Author:** [@amoghb13](https://discourse.julialang.org/u/amoghb13)\
**Replies:** 1\
**Last updated:** [October 8, 2019, 7:34am UTC](https://discourse.julialang.org/t/how-to-represent-binary-array-slot-occupied-1-slot-open-0-in-the-form-of-colored-squares/29631 "2019-10-08T07:34:38Z")

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Hi I want to represent a binary (0-1) array in the form of an image. E.g. if A\[1,1\] = 1, then square \[1,1\[ would be represented as black colored square otherwise it will be represented as white colored square if A\[1,1\] =…

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## [Images.jl not working with JuMP output in for loop](https://discourse.julialang.org/t/images-jl-not-working-with-jump-output-in-for-loop/29630)

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**Author:** [@amoghb13](https://discourse.julialang.org/u/amoghb13)\
**Replies:** 1\
**Last updated:** [October 8, 2019, 7:30am UTC](https://discourse.julialang.org/t/images-jl-not-working-with-jump-output-in-for-loop/29630 "2019-10-08T07:30:46Z")

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I am trying to represent a matrix as black and white squares. Example: This works for me for one time. using Colors, Images y = \[0.5 0.5; 0.7 0.3\] imgg = Gray.(y) This does not work in following case: function abc(…

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## [Passing gradient to Optim](https://discourse.julialang.org/t/passing-gradient-to-optim/29635)

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**Author:** [@ASF](https://discourse.julialang.org/u/ASF)\
**Replies:** 4\
**Last updated:** [October 8, 2019, 7:12am UTC](https://discourse.julialang.org/t/passing-gradient-to-optim/29635 "2019-10-08T07:12:52Z")

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i have the following code: solution = Optim.minimizer(optimize(θ-\>J(X,θ),θ,g!,LBFGS()))) where X,θ are arrays and g! is the gradient function. I get the following error only when trying to specify the gradient function…

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## [Working with machine precision](https://discourse.julialang.org/t/working-with-machine-precision/29576)

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**Author:** [@aahaselgrove](https://discourse.julialang.org/u/aahaselgrove)\
**Replies:** 10\
**Last updated:** [October 8, 2019, 6:54am UTC](https://discourse.julialang.org/t/working-with-machine-precision/29576 "2019-10-08T06:54:54Z")

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If I execute 3\*0.1, Julia prints the value as 0.30000000000000004. I believe the inaccuracy is caused by machine precision, but it doesn’t seem useful to me that Julia would display this. I also note that I have never en…

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## [Debugging Pane with Non-Functions](https://discourse.julialang.org/t/debugging-pane-with-non-functions/29612)

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**Author:** [@duncanam](https://discourse.julialang.org/u/duncanam)\
**Replies:** 3\
**Last updated:** [October 8, 2019, 6:37am UTC](https://discourse.julialang.org/t/debugging-pane-with-non-functions/29612 "2019-10-08T06:37:08Z")

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Hello, Coming from a MATLAB background, I was a little surprised that Juno does not allow for the debugging of non-functions. Most of my work is done within simple scripts that import data, perform analysis on that data…

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## [FeatureSelector in MLJ Learning Networks](https://discourse.julialang.org/t/featureselector-in-mlj-learning-networks/29591)

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**Author:** [@petrost](https://discourse.julialang.org/u/petrost)\
**Replies:** 4\
**Last updated:** [October 8, 2019, 6:21am UTC](https://discourse.julialang.org/t/featureselector-in-mlj-learning-networks/29591 "2019-10-08T06:21:01Z")

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I am trying to build a simple learning network using MLJ, but the FeatureSelector() is not recognized as a valid model used on a node. Is there any alternative to that? In general, is there a way I can perform column-wi…

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## [Adding limits to the Y-axis for SymPy.jl plots](https://discourse.julialang.org/t/adding-limits-to-the-y-axis-for-sympy-jl-plots/29571)

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**Author:** [@00krishna](https://discourse.julialang.org/u/00krishna)\
**Replies:** 4\
**Last updated:** [October 8, 2019, 1:09am UTC](https://discourse.julialang.org/t/adding-limits-to-the-y-axis-for-sympy-jl-plots/29571 "2019-10-08T01:09:31Z")

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I was using SymPy.jl to plot the phase flow of some simple dynamical systems. But I ran into an issue when plotting a particular equation with some discontinuities. \\dot{\\theta} = \\frac{\\sin{\\theta}}{\\mu + \\sin{\\theta}…

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## [Consistent performance difference but identical LLVM IR](https://discourse.julialang.org/t/consistent-performance-difference-but-identical-llvm-ir/29620)

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**Author:** [@milesf](https://discourse.julialang.org/u/milesf)\
**Replies:** 4\
**Last updated:** [October 8, 2019, 12:20am UTC](https://discourse.julialang.org/t/consistent-performance-difference-but-identical-llvm-ir/29620 "2019-10-08T00:20:35Z")

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I am attempting to write a high-performance round-up function that treats Int64 and UInt64 identically. The compiled output is the same, but performance is always worse with UInt. It’s only a 10% difference, but it’s sur…

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## [Seg fault when saving files with JLD2 in WSL](https://discourse.julialang.org/t/seg-fault-when-saving-files-with-jld2-in-wsl/13656)

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**Author:** [@111](https://discourse.julialang.org/u/111)\
**Replies:** 7\
**Last updated:** [October 7, 2019, 10:55pm UTC](https://discourse.julialang.org/t/seg-fault-when-saving-files-with-jld2-in-wsl/13656 "2019-10-07T22:55:21Z")

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The installation of JLD2 in WSL is passed successfully. However, the test code goes wrong: using JLD2, FileIO hello = "world" foo = :bar @save "example.jld2" hello foo The error message is: signal (11): Segmentation f…

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## [Predefined array too large](https://discourse.julialang.org/t/predefined-array-too-large/29623)

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**Author:** [@squirrel](https://discourse.julialang.org/u/squirrel)\
**Replies:** 2\
**Last updated:** [October 7, 2019, 10:17pm UTC](https://discourse.julialang.org/t/predefined-array-too-large/29623 "2019-10-07T22:17:49Z")

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I predefined a vector E to be the same size as vector D. E = typeof(D)(undef, length(D)) In most cases, I expect E to have the same number of elements as D, but I still want to be able to handle the case where E has fe…

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## [How to define a condition expression](https://discourse.julialang.org/t/how-to-define-a-condition-expression/29622)

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**Author:** [@Lyupinpin](https://discourse.julialang.org/u/Lyupinpin)\
**Replies:** 2\
**Last updated:** [October 7, 2019, 10:09pm UTC](https://discourse.julialang.org/t/how-to-define-a-condition-expression/29622 "2019-10-07T22:09:19Z")

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Like if there exsis a file named “abc” then else end

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## [Sigmoid function in Julia](https://discourse.julialang.org/t/sigmoid-function-in-julia/29594)

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**Author:** [@hasanOryx](https://discourse.julialang.org/u/hasanOryx)\
**Replies:** 5\
**Last updated:** [October 7, 2019, 2:35pm UTC](https://discourse.julialang.org/t/sigmoid-function-in-julia/29594 "2019-10-07T14:35:48Z")

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I’m trying to write the sigmoid function as below, but did not work: function sigmoid(z::Array) return 1.0 ./ (1.0 + exp(-z)) end; Knowing that the below is working fine, but I’m looking for a short way to write it…

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## [Broadcast for Array of Array](https://discourse.julialang.org/t/broadcast-for-array-of-array/29604)

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**Author:** [@hasanOryx](https://discourse.julialang.org/u/hasanOryx)\
**Replies:** 16\
**Last updated:** [October 7, 2019, 7:46pm UTC](https://discourse.julialang.org/t/broadcast-for-array-of-array/29604 "2019-10-07T19:46:06Z")

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I’ve the below function sigmoid(z::Real) = one(z) / (one(z) + exp(-z)) And want to broadcast it for all the element of x, where: X = \[ \[1, 2, 3\], \[3, 4, 5\], \[5, 6, 7\] \] I tried…

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## [Where is my mistake in converting this python code into Julia](https://discourse.julialang.org/t/where-is-my-mistake-in-converting-this-python-code-into-julia/29616)

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**Author:** [@hasanOryx](https://discourse.julialang.org/u/hasanOryx)\
**Replies:** 8\
**Last updated:** [October 7, 2019, 7:39pm UTC](https://discourse.julialang.org/t/where-is-my-mistake-in-converting-this-python-code-into-julia/29616 "2019-10-07T19:39:40Z")

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I’m trying to convert the python code(left) into Julia (right), python code is working fine, but Julia code gave an error at the highlighted line l1\_delta = ...: DimensionMismatch("A has dimensions (4,1) but B has dimen…

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## [Weird PackageCompiler problem with parallel builds](https://discourse.julialang.org/t/weird-packagecompiler-problem-with-parallel-builds/29505)

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**Author:** [@dhazeghi](https://discourse.julialang.org/u/dhazeghi)\
**Replies:** 1\
**Last updated:** [October 7, 2019, 7:32pm UTC](https://discourse.julialang.org/t/weird-packagecompiler-problem-with-parallel-builds/29505 "2019-10-07T19:32:40Z")

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Hello, we recently tried to update from PackageCompiler v0.6.0 to v0.6.4 and we’re hitting a weird problem. Because it takes 3-5 minutes to build a binary and we have half a dozen binaries to build, we fire off a bunch…

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## [How to convert Cholesky {Float64,Array{Float64,2}} to Array{Float64,2} in julia](https://discourse.julialang.org/t/how-to-convert-cholesky-float64-array-float64-2-to-array-float64-2-in-julia/29536)

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**Author:** [@shiva](https://discourse.julialang.org/u/shiva)\
**Replies:** 4\
**Last updated:** [October 7, 2019, 7:05pm UTC](https://discourse.julialang.org/t/how-to-convert-cholesky-float64-array-float64-2-to-array-float64-2-in-julia/29536 "2019-10-07T19:05:52Z")

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Hello, I am using Julia 1.0.4 to do a cholesky decomposition I wrote the following code: using LinearAlgebra A=\[1 0 1; 0 2 0; 1 0 3\]; BB=cholesky(A); and the result is: BB=Cholesky{Float64,Array{Float64,2}}(\[1.0 0.…

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## [Juno, toolbar is not shown correctly](https://discourse.julialang.org/t/juno-toolbar-is-not-shown-correctly/29538)

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**Author:** [@zhangliye](https://discourse.julialang.org/u/zhangliye)\
**Replies:** 8\
**Last updated:** [October 7, 2019, 6:37pm UTC](https://discourse.julialang.org/t/juno-toolbar-is-not-shown-correctly/29538 "2019-10-07T18:37:55Z")

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I installed Juno according to the instruction. But not all of the tool bar buttons are shown as following. I have used VS code for several months, because of the bugs in Juno. I like some features of Juno but always …

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## [Modifying hotstart of a variable](https://discourse.julialang.org/t/modifying-hotstart-of-a-variable/29609)

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**Author:** [@gobs](https://discourse.julialang.org/u/gobs)\
**Replies:** 1\
**Last updated:** [October 7, 2019, 6:22pm UTC](https://discourse.julialang.org/t/modifying-hotstart-of-a-variable/29609 "2019-10-07T18:22:48Z")

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I would like to modify the hot start of a variable. I’ve given an minimum working example below: using JuMP, Gurobi, Ipopt m = Model(with\_optimizer(Ipopt.Optimizer)) @variable(m, x, start = 0) # hot start @constraint(m…

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## [Help with array multiplication](https://discourse.julialang.org/t/help-with-array-multiplication/29611)

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**Author:** [@hasanOryx](https://discourse.julialang.org/u/hasanOryx)\
**Replies:** 1\
**Last updated:** [October 7, 2019, 5:53pm UTC](https://discourse.julialang.org/t/help-with-array-multiplication/29611 "2019-10-07T17:53:13Z")

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I aware that to multiple arrays, dimensions should match as: A: array of (x,y) , B: array of (y,z) In Python below is working fine: X = np.array(\[ \[0,0,1\], \[0,1,1\], \[1,0,1\], \[1,1,1\] …

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## [JuMP 0.19 installed by default](https://discourse.julialang.org/t/jump-0-19-installed-by-default/29588)

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**Author:** [@leclere](https://discourse.julialang.org/u/leclere)\
**Replies:** 6\
**Last updated:** [October 7, 2019, 5:12pm UTC](https://discourse.julialang.org/t/jump-0-19-installed-by-default/29588 "2019-10-07T17:12:14Z")

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Hello, setting up my julia environnement from a Jupyter notebook (Julia 1.0.2) I get JuMP 0.19 when using Pkg.add(“JuMP”) while 0.20 is presented as stable and compatible with Julia 1.0. Can someone tell me if it is …

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## [Generalist and "systems" programmer with contributions to the Julia ecosystem for hire](https://discourse.julialang.org/t/generalist-and-systems-programmer-with-contributions-to-the-julia-ecosystem-for-hire/29607)

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**Author:** [@richiejp](https://discourse.julialang.org/u/richiejp)\
**Replies:** 0\
**Last updated:** [October 7, 2019, 5:03pm UTC](https://discourse.julialang.org/t/generalist-and-systems-programmer-with-contributions-to-the-julia-ecosystem-for-hire/29607 "2019-10-07T17:03:54Z")

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Generalist and “systems” software engineer. Experience with every part of the software stack from the hardware up. What follows are some of my open-source endeavors which easily come to mind: JDP: A highly-available…

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## [DBSCAN using Hamming Distance Metric](https://discourse.julialang.org/t/dbscan-using-hamming-distance-metric/29606)

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**Author:** [@Mohamed\_Ismail](https://discourse.julialang.org/u/Mohamed_Ismail)\
**Replies:** 0\
**Last updated:** [October 7, 2019, 4:49pm UTC](https://discourse.julialang.org/t/dbscan-using-hamming-distance-metric/29606 "2019-10-07T16:49:50Z")

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I would like to use Clustering.DBSCAN and specify my own distance metric. Specifically, I want to use Hamming distance. The current DBSCAN interfaces do not seem to provide such option? Is there a workaround for this? …

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## [Error with Pkg.add("Libdl")](https://discourse.julialang.org/t/error-with-pkg-add-libdl/29508)

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**Author:** [@tommaso16](https://discourse.julialang.org/u/tommaso16)\
**Replies:** 2\
**Last updated:** [October 7, 2019, 4:33pm UTC](https://discourse.julialang.org/t/error-with-pkg-add-libdl/29508 "2019-10-07T16:33:54Z")

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Hello, I am trying to run the command include(“setup.jl”) (referring to this code https://github.com/XiaojingGeorgeZhang/H-OBCA) but I get the error INFO: Precompiling module PyPlot. WARNING: could not import Base.push…

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## [Groupreduce of DataFrame with empty group](https://discourse.julialang.org/t/groupreduce-of-dataframe-with-empty-group/29599)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 7\
**Last updated:** [October 7, 2019, 3:52pm UTC](https://discourse.julialang.org/t/groupreduce-of-dataframe-with-empty-group/29599 "2019-10-07T15:52:37Z")

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I have a DataFrame df: df = DataFrame(a = repeat(\[1, 2, 3, 4\], outer=\[2\]), b = repeat(\[2, 1\], outer=\[4\]), c = 1:8); I want to apply the following operation: operator=(:a =\> …

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## [Read lines from command and kill the process](https://discourse.julialang.org/t/read-lines-from-command-and-kill-the-process/29600)

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**Author:** [@sdewaele](https://discourse.julialang.org/u/sdewaele)\
**Replies:** 0\
**Last updated:** [October 7, 2019, 3:15pm UTC](https://discourse.julialang.org/t/read-lines-from-command-and-kill-the-process/29600 "2019-10-07T15:15:58Z")

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I would like to do the following: Start an external command Read lines from the command If the line contains a certain text, kill the external command Return once all lines are read Is there a simple way to achieve th…

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## [OpenBLAS vs. "for loops" demo](https://discourse.julialang.org/t/openblas-vs-for-loops-demo/29581)

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**Author:** [@Iulian.Cioarca](https://discourse.julialang.org/u/Iulian.Cioarca)\
**Replies:** 6\
**Last updated:** [October 7, 2019, 2:07pm UTC](https://discourse.julialang.org/t/openblas-vs-for-loops-demo/29581 "2019-10-07T14:07:12Z")

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I am preparing a presentation/demo for an upcoming meetup and want to showcase that “for loops” in Julia are fast. How fast? Fast enough to write simple code that compares to BLAS routines. So I decided to implement a “…

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