# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1509

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

**Page:** 1510

---

## [Multithreading on Cartesian products](https://discourse.julialang.org/t/multithreading-on-cartesian-products/54009)

<div class="topic-metadata">

**Author:** [@gregory](https://discourse.julialang.org/u/gregory)\
**Replies:** 22\
**Last updated:** [January 28, 2021, 9:43pm UTC](https://discourse.julialang.org/t/multithreading-on-cartesian-products/54009 "2021-01-28T21:43:20Z")

</div>

Suppose I have an array of 5 coordinates each ranging from (1:5) so that myarr = \[1:5 for i in 1 : 5\] is of length 3125 (in reality this list can be much larger and each element could range over different values). I am …

---

## [Zygote differentiation issues](https://discourse.julialang.org/t/zygote-differentiation-issues/54130)

<div class="topic-metadata">

**Author:** [@adhikarirsr](https://discourse.julialang.org/u/adhikarirsr)\
**Replies:** 7\
**Last updated:** [January 28, 2021, 8:12pm UTC](https://discourse.julialang.org/t/zygote-differentiation-issues/54130 "2021-01-28T20:12:32Z")

</div>

In an attempt to replicate what I saw here: " The impact of differentiable programming: how ∂P is enabling new science in Julia" function g(x) if x \< 0 print("Enter function name: ") getfield(Base, S…

---

## [Custom row indexing in DataFrames](https://discourse.julialang.org/t/custom-row-indexing-in-dataframes/53959)

<div class="topic-metadata">

**Author:** [@Impressium](https://discourse.julialang.org/u/Impressium)\
**Replies:** 2\
**Last updated:** [January 28, 2021, 6:04pm UTC](https://discourse.julialang.org/t/custom-row-indexing-in-dataframes/53959 "2021-01-28T18:04:17Z")

</div>

Hey everybody :slight\_smile: Given a DataFrame df with columns I, A and C. Is there an way to set I as row index such that I can use df\[i,:\]or df\[i,a\] with i in I and a in A.

---

## [New Blog post live: "Apache Arrow Support in Julia"](https://discourse.julialang.org/t/new-blog-post-live-apache-arrow-support-in-julia/54135)

<div class="topic-metadata">

**Author:** [@logankilpatrick](https://discourse.julialang.org/u/logankilpatrick)\
**Replies:** 0\
**Last updated:** [January 28, 2021, 4:59pm UTC](https://discourse.julialang.org/t/new-blog-post-live-apache-arrow-support-in-julia/54135 "2021-01-28T16:59:10Z")

</div>

A new blog post titled: “Apache Arrow Support in Julia” was just posted on the Julia Language’s official blog. Check it out here: Apache Arrow Support in Julia and let us know your thoughts!

---

## [The case of disappearing double dash](https://discourse.julialang.org/t/the-case-of-disappearing-double-dash/54126)

<div class="topic-metadata">

**Author:** [@matklad](https://discourse.julialang.org/u/matklad)\
**Replies:** 2\
**Last updated:** [January 28, 2021, 4:27pm UTC](https://discourse.julialang.org/t/the-case-of-disappearing-double-dash/54126 "2021-01-28T16:27:42Z")

</div>

I have the following julia script: #!/usr/bin/env julia println(ARGS) Heres’s the output if I run it with an -- argument: 18:41:14|~/tmp λ ./main.jl -a --b -- c \["-a", "--b", "c"\] What happened to --? Just in case, …

---

## [Fast and simple search for an object by field value, like in a database](https://discourse.julialang.org/t/fast-and-simple-search-for-an-object-by-field-value-like-in-a-database/54127)

<div class="topic-metadata">

**Author:** [@andrey2185](https://discourse.julialang.org/u/andrey2185)\
**Replies:** 2\
**Last updated:** [January 28, 2021, 4:24pm UTC](https://discourse.julialang.org/t/fast-and-simple-search-for-an-object-by-field-value-like-in-a-database/54127 "2021-01-28T16:24:52Z")

</div>

Hello, I need a fast and simple search for an object by field value, like in a database. for example, search for an object with the maximum field value, search by object field value search object with next value up W…

---

## [Pkg.add("plots") doesn't work](https://discourse.julialang.org/t/pkg-add-plots-doesnt-work/54015)

<div class="topic-metadata">

**Author:** [@Firas\_Bejar](https://discourse.julialang.org/u/Firas_Bejar)\
**Replies:** 3\
**Last updated:** [January 28, 2021, 3:46pm UTC](https://discourse.julialang.org/t/pkg-add-plots-doesnt-work/54015 "2021-01-28T15:46:11Z")

</div>

I am a total beginner with julia and I’ve been trying to make some simple plots using the following commands: import Pkg using Pkg Pkg.add(“Plots”) but everytime I get the same msg: Unsatisfiable requirements detect…

---

## [Addprocs gives connection refused to a docker container on raspberry pi](https://discourse.julialang.org/t/addprocs-gives-connection-refused-to-a-docker-container-on-raspberry-pi/35640)

<div class="topic-metadata">

**Author:** [@rbontekoe](https://discourse.julialang.org/u/rbontekoe)\
**Replies:** 2\
**Last updated:** [January 28, 2021, 3:46pm UTC](https://discourse.julialang.org/t/addprocs-gives-connection-refused-to-a-docker-container-on-raspberry-pi/35640 "2021-01-28T15:46:09Z")

</div>

I have a docker container running on my Ubuntu 18.04 laptop and a docker container on my Raspberry Pi 3+. Julia is installed the same on both containers (/home/rob/julia/julia-1.3.1/bin/). The Dockerfile I use for both …

---

## [What is the best way to override a function in different modules?](https://discourse.julialang.org/t/what-is-the-best-way-to-override-a-function-in-different-modules/54111)

<div class="topic-metadata">

**Author:** [@stefkuypers](https://discourse.julialang.org/u/stefkuypers)\
**Replies:** 4\
**Last updated:** [January 28, 2021, 3:39pm UTC](https://discourse.julialang.org/t/what-is-the-best-way-to-override-a-function-in-different-modules/54111 "2021-01-28T15:39:11Z")

</div>

Hi, What is the best practice to make sure to avoid the following type of warnings? WARNING: both ABM\_Sim and Production export "produce!"; uses of it in module Main must be qualified I have 2 modules where I defined …

---

## [Passing constant configuration values to modules](https://discourse.julialang.org/t/passing-constant-configuration-values-to-modules/28551)

<div class="topic-metadata">

**Author:** [@aahaselgrove](https://discourse.julialang.org/u/aahaselgrove)\
**Replies:** 7\
**Last updated:** [January 28, 2021, 3:33pm UTC](https://discourse.julialang.org/t/passing-constant-configuration-values-to-modules/28551 "2021-01-28T15:33:25Z")

</div>

I am working on a numerical optimisation project with Julia in a Jupyter notebook. My current workflow is to define the problem size with some global constants at the top of the notebook (eg. const N = 20), which are the…

---

## [Defining a custom constructor for a type alias?](https://discourse.julialang.org/t/defining-a-custom-constructor-for-a-type-alias/54017)

<div class="topic-metadata">

**Author:** [@maajdl](https://discourse.julialang.org/u/maajdl)\
**Replies:** 8\
**Last updated:** [January 28, 2021, 2:46pm UTC](https://discourse.julialang.org/t/defining-a-custom-constructor-for-a-type-alias/54017 "2021-01-28T14:46:51Z")

</div>

This snippet is invalid: boo = Array{Stuff,1} function boo(x,y,z) someStuff = ..... return someStuff end It returns this error: cannot define function boo; it already has a value Would you have any idea ab…

---

## [Get conditional kernel densities in julia](https://discourse.julialang.org/t/get-conditional-kernel-densities-in-julia/54086)

<div class="topic-metadata">

**Author:** [@claudio20497](https://discourse.julialang.org/u/claudio20497)\
**Replies:** 0\
**Last updated:** [January 27, 2021, 9:53pm UTC](https://discourse.julialang.org/t/get-conditional-kernel-densities-in-julia/54086 "2021-01-27T21:53:55Z")

</div>

Hello, I was wondering if there is a method to get a conditional distribution out of a multivariate kde in julia, preferably using the package KernelDensityEstimate.jl. So say for example that I have the following code…

---

## [Looking for a maintainer for SimpleDirectMediaLayer.jl](https://discourse.julialang.org/t/looking-for-a-maintainer-for-simpledirectmedialayer-jl/53596)

<div class="topic-metadata">

**Author:** [@jonathanBieler](https://discourse.julialang.org/u/jonathanBieler)\
**Replies:** 4\
**Last updated:** [January 28, 2021, 1:51pm UTC](https://discourse.julialang.org/t/looking-for-a-maintainer-for-simpledirectmedialayer-jl/53596 "2021-01-28T13:51:42Z")

</div>

I made bindings for SDL2 (a popular multimedia library) a couple of years ago but I don’t have much time to maintain it anymore (I also don’t use it myself, which doesn’t help). I’d be happy to transfer the package to an…

---

## [Puzzled by scope rules](https://discourse.julialang.org/t/puzzled-by-scope-rules/54103)

<div class="topic-metadata">

**Author:** [@askvorts](https://discourse.julialang.org/u/askvorts)\
**Replies:** 9\
**Last updated:** [January 28, 2021, 1:31pm UTC](https://discourse.julialang.org/t/puzzled-by-scope-rules/54103 "2021-01-28T13:31:41Z")

</div>

When running function ten() j = 1 while j \< 10 global j += 1 end end println(ten()) one gets ERROR: LoadError: UndefVarError: j not defined Which would be the correct way to define j? The block in…

---

## [Empty result when comparing incompatible types](https://discourse.julialang.org/t/empty-result-when-comparing-incompatible-types/54102)

<div class="topic-metadata">

**Author:** [@jzr](https://discourse.julialang.org/u/jzr)\
**Replies:** 2\
**Last updated:** [January 28, 2021, 1:23pm UTC](https://discourse.julialang.org/t/empty-result-when-comparing-incompatible-types/54102 "2021-01-28T13:23:48Z")

</div>

Often I am filtering a vector or joining dataframes and I use the wrong type and get an empty result. For example with Base: rows = \[ (month = 01, x = 15.4), (month = 02, x = 38.3), \] filter(x-\>x.month == "January", …

---

## [Help me in using Plots Pkg, scatter](https://discourse.julialang.org/t/help-me-in-using-plots-pkg-scatter/54115)

<div class="topic-metadata">

**Author:** [@Mahnazi](https://discourse.julialang.org/u/Mahnazi)\
**Replies:** 1\
**Last updated:** [January 28, 2021, 1:18pm UTC](https://discourse.julialang.org/t/help-me-in-using-plots-pkg-scatter/54115 "2021-01-28T13:18:08Z")

</div>

using XLSX using Plots Data = XLSX.readxlsx(“VRPTW.xlsx”) Xd=Data\[“C101!E3:E28”\] Yd=Data\[“C101!F3:F28”\] #Display the data scatter(Xd,Yd) but Cannot convert Array{Any,2} to series data for plotting error(::String…

---

## [Calling Julia functions from a multi-threading scheduler written in C?](https://discourse.julialang.org/t/calling-julia-functions-from-a-multi-threading-scheduler-written-in-c/54114)

<div class="topic-metadata">

**Author:** [@stustd](https://discourse.julialang.org/u/stustd)\
**Replies:** 1\
**Last updated:** [January 28, 2021, 1:16pm UTC](https://discourse.julialang.org/t/calling-julia-functions-from-a-multi-threading-scheduler-written-in-c/54114 "2021-01-28T13:16:18Z")

</div>

I have a scheduler written in C that repetitively executes batches if C functions in multi-threaded fashion: Mutually exclusive groups of C functions update one reactor state (i.e. the total set of C functions is parti…

---

## [Error in adding Plots Pkg](https://discourse.julialang.org/t/error-in-adding-plots-pkg/54053)

<div class="topic-metadata">

**Author:** [@Mahnazi](https://discourse.julialang.org/u/Mahnazi)\
**Replies:** 7\
**Last updated:** [January 28, 2021, 12:49pm UTC](https://discourse.julialang.org/t/error-in-adding-plots-pkg/54053 "2021-01-28T12:49:28Z")

</div>

Plots I have just started learning Julia. I am using Windows 10 I have a problem installing the Plots package. julia\> Pkg.add(“Plots”) Updating registry at C:\\Users\\HP\\.julia\\registries\\General Updating registry at…

---

## [Why is julialang.org/blog not aggregated into juliabloggers.com?](https://discourse.julialang.org/t/why-is-julialang-org-blog-not-aggregated-into-juliabloggers-com/13274)

<div class="topic-metadata">

**Author:** [@xiaoweiz](https://discourse.julialang.org/u/xiaoweiz)\
**Replies:** 10\
**Last updated:** [January 28, 2021, 12:34pm UTC](https://discourse.julialang.org/t/why-is-julialang-org-blog-not-aggregated-into-juliabloggers-com/13274 "2021-01-28T12:34:38Z")

</div>

I’ve been using RSS to receive updates from The Julia Language Blog for some time. But since the recent update of julialang.com, the RSS function of its blog stopped working. Then I became aware of juliabloggers.com, whi…

---

## [\[ANN\] Publish.jl](https://discourse.julialang.org/t/ann-publish-jl/45500)

<div class="topic-metadata">

**Author:** [@mike](https://discourse.julialang.org/u/mike)\
**Replies:** 25\
**Last updated:** [January 28, 2021, 10:13am UTC](https://discourse.julialang.org/t/ann-publish-jl/45500 "2021-01-28T10:13:46Z")

</div>

Hi all, I’m pleased to announce the (very early) 0.1 release of Publish.jl. An experimental package in the same ecosystem “space” as Documenter.jl. It’s purpose is to explore alternative design decisions (potentially ma…

---

## [Scope of dictionary-generated variables](https://discourse.julialang.org/t/scope-of-dictionary-generated-variables/54072)

<div class="topic-metadata">

**Author:** [@vavrines](https://discourse.julialang.org/u/vavrines)\
**Replies:** 10\
**Last updated:** [January 28, 2021, 8:05am UTC](https://discourse.julialang.org/t/scope-of-dictionary-generated-variables/54072 "2021-01-28T08:05:47Z")

</div>

Saying I’d like to create variables from a dictionary. With the following codes, I found the former generated variables aren’t deliminated after each run of the function. D1 = Dict("a" =\> 1, "b" =\> 2) D2 = Dict("a" =\> …

---

## [Unable to compute gradient of loss of my model with sciml\_train](https://discourse.julialang.org/t/unable-to-compute-gradient-of-loss-of-my-model-with-sciml-train/49572)

<div class="topic-metadata">

**Author:** [@TomCif](https://discourse.julialang.org/u/TomCif)\
**Replies:** 5\
**Last updated:** [January 28, 2021, 6:38am UTC](https://discourse.julialang.org/t/unable-to-compute-gradient-of-loss-of-my-model-with-sciml-train/49572 "2021-01-28T06:38:36Z")

</div>

Hello, I’m facing an error for which I can’t find any solution or reporting. I’m trying to train a model defined by an ODE for which i solve the adjoint problem using concrete\_solve. function initial\_value\_problem(du:…

---

## [Permutation of n arrays](https://discourse.julialang.org/t/permutation-of-n-arrays/54098)

<div class="topic-metadata">

**Author:** [@trathi](https://discourse.julialang.org/u/trathi)\
**Replies:** 6\
**Last updated:** [January 28, 2021, 6:26am UTC](https://discourse.julialang.org/t/permutation-of-n-arrays/54098 "2021-01-28T06:26:34Z")

</div>

I have n array of arrays and I want to generate a single array containing all permutations of these arrays. For example (with 2 arrays): a=\[\[1,2,3\],\[4,5,6\]\] b=\[\[7,8,9\],\[10,11,12\]\] c=\[\[\[1,2,3\],\[7,8,9\]\],\[\[1,2,3\],\[10,11,12…

---

## [Generating Structs at Runtime; Tips and Tricks?](https://discourse.julialang.org/t/generating-structs-at-runtime-tips-and-tricks/54096)

<div class="topic-metadata">

**Author:** [@olynch](https://discourse.julialang.org/u/olynch)\
**Replies:** 3\
**Last updated:** [January 28, 2021, 3:35am UTC](https://discourse.julialang.org/t/generating-structs-at-runtime-tips-and-tricks/54096 "2021-01-28T03:35:25Z")

</div>

Hello all, For various reasons, I would like to write a macro that evals code at runtime to construct a custom struct. The problem is that the code that I am evaling is not hygenically generated, because it comes out of…

---

## [Julia Plots savefig whitespace issue](https://discourse.julialang.org/t/julia-plots-savefig-whitespace-issue/54081)

<div class="topic-metadata">

**Author:** [@gideonsimpson](https://discourse.julialang.org/u/gideonsimpson)\
**Replies:** 3\
**Last updated:** [January 28, 2021, 3:21am UTC](https://discourse.julialang.org/t/julia-plots-savefig-whitespace-issue/54081 "2021-01-28T03:21:57Z")

</div>

When saving figures generated by Plots.jl with the pyplot, is there a straightforward way to trim the extra whitespace when I call savefig?

---

## [Question regarding COSMO Convergence](https://discourse.julialang.org/t/question-regarding-cosmo-convergence/53996)

<div class="topic-metadata">

**Author:** [@Y\_Li](https://discourse.julialang.org/u/Y_Li)\
**Replies:** 1\
**Last updated:** [January 28, 2021, 1:16am UTC](https://discourse.julialang.org/t/question-regarding-cosmo-convergence/53996 "2021-01-28T01:16:31Z")

</div>

Hi, I have a question regarding COSMO package, this is my first time using it, what steps can I take when my code does not converge(but in reality it should)? It delivers message “Max\_iter\_reached” and stops at a value …

---

## [When can a single-call optimization be used?](https://discourse.julialang.org/t/when-can-a-single-call-optimization-be-used/54089)

<div class="topic-metadata">

**Author:** [@jzr](https://discourse.julialang.org/u/jzr)\
**Replies:** 3\
**Last updated:** [January 28, 2021, 12:35am UTC](https://discourse.julialang.org/t/when-can-a-single-call-optimization-be-used/54089 "2021-01-28T00:35:46Z")

</div>

function func(x) sum(x) / sum(x) end xs = rand(0:.1:1, 1000) @code\_typed func(xs) julia\> @code\_typed func(xs) CodeInfo( 1 ── %1 = Base.identity::typeof(identity) │ %2 = Base.add\_sum::typeof(Base.add\_sum) │ …

---

## [Plot integrals](https://discourse.julialang.org/t/plot-integrals/54087)

<div class="topic-metadata">

**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 6\
**Last updated:** [January 27, 2021, 11:27pm UTC](https://discourse.julialang.org/t/plot-integrals/54087 "2021-01-27T23:27:53Z")

</div>

I can plot derivatives using ForwardDiff and Plots using ForwardDiff using Plots f(x)=x^2 df(x)=ForwardDiff.derivative(f(x), x) plot(df) but QuadGK.jl gives two answers so this method won’t work. Is there a way to pl…

---

## [\[ANN\] Announcing QuasinormalModes.jl](https://discourse.julialang.org/t/ann-announcing-quasinormalmodes-jl/54071)

<div class="topic-metadata">

**Author:** [@lucass-carneiro](https://discourse.julialang.org/u/lucass-carneiro)\
**Replies:** 4\
**Last updated:** [January 27, 2021, 11:11pm UTC](https://discourse.julialang.org/t/ann-announcing-quasinormalmodes-jl/54071 "2021-01-27T23:11:19Z")

</div>

Hi! I’m announcing my first public Julia package, called QuasinormalModes.jl. It’s primary objective is to compute the discrete eigenvalues of second order ordinary differential equations. It was written with the inten…

---

## [Where should I save Julia in the Linux Tree?](https://discourse.julialang.org/t/where-should-i-save-julia-in-the-linux-tree/53463)

<div class="topic-metadata">

**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 7\
**Last updated:** [January 27, 2021, 10:55pm UTC](https://discourse.julialang.org/t/where-should-i-save-julia-in-the-linux-tree/53463 "2021-01-27T22:55:38Z")

</div>

Thanks so, is this what I do if I want to try 1.6 ? wget https://julialang-s3.julialang.org/bin/linux/x64/1.6.0/julia-1.6.0-beta1-linux-x86\_64.tar.gz tar zxvf julia-1.6.0-beta1-linux-x86\_64.tar.gz

[Previous page](https://discourse.julialang.org/latest.md?page=1508)

[Next page](https://discourse.julialang.org/latest.md?page=1510)