# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1730

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

**Page:** 1731

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## [Two question on Channel operation](https://discourse.julialang.org/t/two-question-on-channel-operation/40626)

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**Author:** [@zhangliye](https://discourse.julialang.org/u/zhangliye)\
**Replies:** 4\
**Last updated:** [June 3, 2020, 4:22am UTC](https://discourse.julialang.org/t/two-question-on-channel-operation/40626 "2020-06-03T04:22:41Z")

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Qestion1: Because the max size of chnl is 0, the following code should be blocked. Why the following code is not blocked? chnl = Channel() do ch foreach(i -\> put!(ch, i), 1:4) # not blocked end; The following is…

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## [Use an external variable inside a loop](https://discourse.julialang.org/t/use-an-external-variable-inside-a-loop/40453)

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**Author:** [@HuascarOk](https://discourse.julialang.org/u/HuascarOk)\
**Replies:** 11\
**Last updated:** [June 3, 2020, 3:15am UTC](https://discourse.julialang.org/t/use-an-external-variable-inside-a-loop/40453 "2020-06-03T03:15:50Z")

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Hello, i need help to use an external variable inside a loop. I’ve been trying for days and i still don’t have an idea of how to use something outside a for inside it, change it and then use it’s new value outside. Here’…

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## [ERROR in adding a package](https://discourse.julialang.org/t/error-in-adding-a-package/40623)

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**Author:** [@xinzhicaishu](https://discourse.julialang.org/u/xinzhicaishu)\
**Replies:** 3\
**Last updated:** [June 3, 2020, 12:40am UTC](https://discourse.julialang.org/t/error-in-adding-a-package/40623 "2020-06-03T00:40:30Z")

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## [Parsing Column values of different types](https://discourse.julialang.org/t/parsing-column-values-of-different-types/40589)

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**Author:** [@Chris\_Anderson](https://discourse.julialang.org/u/Chris_Anderson)\
**Replies:** 2\
**Last updated:** [June 2, 2020, 11:47pm UTC](https://discourse.julialang.org/t/parsing-column-values-of-different-types/40589 "2020-06-02T23:47:40Z")

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I have a side job/project that involves analyzing a large data set. I am leveraging this project to gain competence with programming generally and Julia specifically, meaning the learning curve is steep as I work throug…

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## [How to get dependency information for "to-be-added" packages?](https://discourse.julialang.org/t/how-to-get-dependency-information-for-to-be-added-packages/40632)

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**Author:** [@GregVernon](https://discourse.julialang.org/u/GregVernon)\
**Replies:** 7\
**Last updated:** [June 2, 2020, 9:31pm UTC](https://discourse.julialang.org/t/how-to-get-dependency-information-for-to-be-added-packages/40632 "2020-06-02T21:31:19Z")

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Background: Like many, I have the issue that my work PC is behind a corporate firewall and I am not personally able to create a proxy (not an admin or in cybersec). Additionally, I have to submit approval requests to ap…

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## [Vector of Vectors with different size to one Vector](https://discourse.julialang.org/t/vector-of-vectors-with-different-size-to-one-vector/40534)

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**Author:** [@BMval](https://discourse.julialang.org/u/BMval)\
**Replies:** 9\
**Last updated:** [June 2, 2020, 8:26pm UTC](https://discourse.julialang.org/t/vector-of-vectors-with-different-size-to-one-vector/40534 "2020-06-02T20:26:59Z")

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I am sorry for the easy questions. Would you suggest how to convert: Vector of Vectors with different size to one Vector

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## [Struggles with registering a new package](https://discourse.julialang.org/t/struggles-with-registering-a-new-package/40627)

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**Author:** [@grahamstark](https://discourse.julialang.org/u/grahamstark)\
**Replies:** 3\
**Last updated:** [June 2, 2020, 7:42pm UTC](https://discourse.julialang.org/t/struggles-with-registering-a-new-package/40627 "2020-06-02T19:42:40Z")

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Hi, I’ve been trying to register my first package using JuliaRegistries. My submission was rejected by the bot because I’d entered a dependency version number wrongly. I’ve fixed this but I’m unclear what to do now - do…

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## [Generating equations in ModellingToolkit from infinite series](https://discourse.julialang.org/t/generating-equations-in-modellingtoolkit-from-infinite-series/40244)

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**Author:** [@Bogo](https://discourse.julialang.org/u/Bogo)\
**Replies:** 5\
**Last updated:** [June 2, 2020, 7:28pm UTC](https://discourse.julialang.org/t/generating-equations-in-modellingtoolkit-from-infinite-series/40244 "2020-06-02T19:28:44Z")

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Hi all! I was advised to open this issue as a follow-up of this thread: https://discourse.julialang.org/t/speeding-up-solution-to-the-large-system-of-non-linear-complex-valued-odes/39075 My issue: I am generating nonli…

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## [Apparently incorrect error when going out of bounds on a dataframe](https://discourse.julialang.org/t/apparently-incorrect-error-when-going-out-of-bounds-on-a-dataframe/40622)

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**Author:** [@klaff](https://discourse.julialang.org/u/klaff)\
**Replies:** 2\
**Last updated:** [June 2, 2020, 6:31pm UTC](https://discourse.julialang.org/t/apparently-incorrect-error-when-going-out-of-bounds-on-a-dataframe/40622 "2020-06-02T18:31:41Z")

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julia\> df=DataFrame(rand(3,3)) 3×3 DataFrame │ Row │ x1 │ x2 │ x3 │ │ │ Float64 │ Float64 │ Float64 │ ├─────┼──────────┼──────────┼──────────┤ │ 1 │ 0.505311 │ 0.327654 │ 0.761537 │ │ 2 │ 0.6…

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## [Sigmoid function](https://discourse.julialang.org/t/sigmoid-function/40614)

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**Author:** [@Shirin](https://discourse.julialang.org/u/Shirin)\
**Replies:** 8\
**Last updated:** [June 2, 2020, 6:25pm UTC](https://discourse.julialang.org/t/sigmoid-function/40614 "2020-06-02T18:25:18Z")

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Hello, I have difficulty with getting the derivate (Gradient ) of sigmoid! using Flux sigmoid(x)=1 ./(1 .+exp(.-x)) sigmoid(x)=s d(s)=x .\* (1 .- x) d(\[1 2 3\]) it causes error or not outputting correct number! I w…

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## [How would I check for unique values across many arrays without for loops?](https://discourse.julialang.org/t/how-would-i-check-for-unique-values-across-many-arrays-without-for-loops/40341)

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**Author:** [@Julia1](https://discourse.julialang.org/u/Julia1)\
**Replies:** 7\
**Last updated:** [June 2, 2020, 5:21pm UTC](https://discourse.julialang.org/t/how-would-i-check-for-unique-values-across-many-arrays-without-for-loops/40341 "2020-06-02T17:21:16Z")

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Hi how’s it going? Say I have 3 arrays: X = \[1,2,3,4,5\] Y = \[1,2,3,4\] Z = \[1,2,3,4\] I want to return that of the 5 unique values across X, Y and Z, only the number 5 is truly unique, because it only occurs in 1 arr…

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## [Read CSVs. Build DataFrame with column identifying the original CSV](https://discourse.julialang.org/t/read-csvs-build-dataframe-with-column-identifying-the-original-csv/40523)

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**Author:** [@anon64288406](https://discourse.julialang.org/u/anon64288406)\
**Replies:** 9\
**Last updated:** [June 2, 2020, 3:27pm UTC](https://discourse.julialang.org/t/read-csvs-build-dataframe-with-column-identifying-the-original-csv/40523 "2020-06-02T15:27:56Z")

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I’ve been trying to learn Julia (1.4) by doing something I commonly do with R or Python: Have a bunch of CSVs, each with a year (YYYY) in the filename. Some datasets have columns that aren’t in the other datasets. Read…

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## [Makie: How to hide axes while plotting text](https://discourse.julialang.org/t/makie-how-to-hide-axes-while-plotting-text/40604)

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**Author:** [@themadprogramer](https://discourse.julialang.org/u/themadprogramer)\
**Replies:** 7\
**Last updated:** [June 2, 2020, 3:25pm UTC](https://discourse.julialang.org/t/makie-how-to-hide-axes-while-plotting-text/40604 "2020-06-02T15:25:13Z")

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As I was starting to lose hope in the future of Julia in terms of applicability, I happened to discover Makie.jl and I am loving it so far. A small question I’d like to ask is how one might hide axes, if only plotting t…

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## [How to split up a Float column in array or dataframe (not String)](https://discourse.julialang.org/t/how-to-split-up-a-float-column-in-array-or-dataframe-not-string/40406)

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**Author:** [@HelgavonLichtenstein](https://discourse.julialang.org/u/HelgavonLichtenstein)\
**Replies:** 8\
**Last updated:** [June 2, 2020, 2:43pm UTC](https://discourse.julialang.org/t/how-to-split-up-a-float-column-in-array-or-dataframe-not-string/40406 "2020-06-02T14:43:51Z")

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Hello, there are a few topics about splitting up columns in a Dataframe or Table that are strings e.g. https://discourse.julialang.org/t/juliadb-split-one-column-into-n-columns/20718 https://stackoverflow.com/questions…

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## [Protocols/Interfaces/Traits... or: The "what to implement problem"](https://discourse.julialang.org/t/protocols-interfaces-traits-or-the-what-to-implement-problem/40137)

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**Author:** [@FHell](https://discourse.julialang.org/u/FHell)\
**Replies:** 10\
**Last updated:** [June 2, 2020, 2:22pm UTC](https://discourse.julialang.org/t/protocols-interfaces-traits-or-the-what-to-implement-problem/40137 "2020-06-02T14:22:35Z")

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Hello everyone, I am interested in picking up the “what to implement problem” of defining interfaces/protocols in Julia. In my view the broad issue is: How do I encode invariants and expectations of my code. This is cri…

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## [JuMP conditional constraint](https://discourse.julialang.org/t/jump-conditional-constraint/40575)

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**Author:** [@m.lavaiyan](https://discourse.julialang.org/u/m.lavaiyan)\
**Replies:** 9\
**Last updated:** [June 2, 2020, 2:21pm UTC](https://discourse.julialang.org/t/jump-conditional-constraint/40575 "2020-06-02T14:21:28Z")

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I want to implement a conditional constraint to my model where each non-zero variable, force the next two variables to be zero. In other words, if x\[t\]=0 then x\[t+1\]=0 and x\[t+2\]=0. I tried a quadratic constrain as belo…

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## [Can't get debugging breakpoint in the right frame](https://discourse.julialang.org/t/cant-get-debugging-breakpoint-in-the-right-frame/40613)

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**Author:** [@robsmith11](https://discourse.julialang.org/u/robsmith11)\
**Replies:** 0\
**Last updated:** [June 2, 2020, 1:56pm UTC](https://discourse.julialang.org/t/cant-get-debugging-breakpoint-in-the-right-frame/40613 "2020-06-02T13:56:48Z")

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I’d like to interactively inspect the value of large struct at a certain point in the execution of my program. I am able to use JuliaInterpreter.jl to set a breakpoint, but it seems to be returning the wrong frame. Thi…

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## [Performance issues - Comparison with Matlab](https://discourse.julialang.org/t/performance-issues-comparison-with-matlab/40592)

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**Author:** [@axsano](https://discourse.julialang.org/u/axsano)\
**Replies:** 6\
**Last updated:** [June 2, 2020, 1:08pm UTC](https://discourse.julialang.org/t/performance-issues-comparison-with-matlab/40592 "2020-06-02T13:08:24Z")

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I have the following example of Chebyshev polynomials differentiation matrix in Julia. function cheb(N) N==0 ? (return D=0.0; x=0.0) : (D=0.0; x=0.0) x = cos.(π\*(0:N)./N) c = \[2; ones(N-1); 2\].\*(-1).^(0:N) …

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## [ArgParseSettings() and special characters](https://discourse.julialang.org/t/argparsesettings-and-special-characters/40612)

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**Author:** [@German\_Salazar](https://discourse.julialang.org/u/German_Salazar)\
**Replies:** 0\
**Last updated:** [June 2, 2020, 12:57pm UTC](https://discourse.julialang.org/t/argparsesettings-and-special-characters/40612 "2020-06-02T12:57:45Z")

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I would like to include a special character within the text for the epilog. In the documentation for ArgParseSettings, it is mentioned that one can manually control spaces using ‘\\ua0’. So, I figured I could used the c…

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## [How to use multiple threads (julia \> 1.3) in a for loop saving results in a vector](https://discourse.julialang.org/t/how-to-use-multiple-threads-julia-1-3-in-a-for-loop-saving-results-in-a-vector/40611)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 0\
**Last updated:** [June 2, 2020, 12:50pm UTC](https://discourse.julialang.org/t/how-to-use-multiple-threads-julia-1-3-in-a-for-loop-saving-results-in-a-vector/40611 "2020-06-02T12:50:28Z")

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As I needed quite a few time to learn how to use the new @spawn in Julia \>= 1.3, here is an example on how to use threads on a function that produces something, saving the results to a vector (where order doesn’t matter)…

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## [Julia-VSCode data grid / table](https://discourse.julialang.org/t/julia-vscode-data-grid-table/40605)

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**Author:** [@Humphrey\_Lee](https://discourse.julialang.org/u/Humphrey_Lee)\
**Replies:** 7\
**Last updated:** [June 2, 2020, 11:40am UTC](https://discourse.julialang.org/t/julia-vscode-data-grid-table/40605 "2020-06-02T11:40:26Z")

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How to (guide) enable data grid/ table viewer in VSCode? Saw screenshot of this on julia-vscode homepage but documentation is still empty. Appreciate your advise @davidanthoff. Thanks.

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## [Quadgk not working for potential convert from MATLAB to Julia?](https://discourse.julialang.org/t/quadgk-not-working-for-potential-convert-from-matlab-to-julia/40600)

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**Author:** [@jbpatzer](https://discourse.julialang.org/u/jbpatzer)\
**Replies:** 2\
**Last updated:** [June 2, 2020, 8:56am UTC](https://discourse.julialang.org/t/quadgk-not-working-for-potential-convert-from-matlab-to-julia/40600 "2020-06-02T08:56:47Z")

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In MATLAB, quadgk(@(s) (exp(-s.^2)-1)./s.^2,0,1) gives me 0.8615, consistent with the correct answer, 1 - 1/e -sqrt(pi) erf(1). In Julia, quadgk(s-\> exp(-s.^2-1.0)./s.^2,0.0,1.0) gives me ERROR: DomainError with 4.773…

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## [How to handle weakrefstrings when importing a CSV file](https://discourse.julialang.org/t/how-to-handle-weakrefstrings-when-importing-a-csv-file/40563)

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**Author:** [@JasonHall](https://discourse.julialang.org/u/JasonHall)\
**Replies:** 13\
**Last updated:** [June 2, 2020, 8:16am UTC](https://discourse.julialang.org/t/how-to-handle-weakrefstrings-when-importing-a-csv-file/40563 "2020-06-02T08:16:10Z")

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I am using Julia 1.4 and CSV 0.62. I have a CSV file that has a column with some JSON in it (e.g. {"type":"Point","coordinates":\[-3.73610686,58.3917902\]})\`. When I look at the data type I am told it is of type String. …

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## [Libdl : libifport.so.5: cannot open shared object file: No such file or directory](https://discourse.julialang.org/t/libdl-libifport-so-5-cannot-open-shared-object-file-no-such-file-or-directory/40598)

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**Author:** [@Lian\_Yunlong](https://discourse.julialang.org/u/Lian_Yunlong)\
**Replies:** 1\
**Last updated:** [June 2, 2020, 8:07am UTC](https://discourse.julialang.org/t/libdl-libifport-so-5-cannot-open-shared-object-file-no-such-file-or-directory/40598 "2020-06-02T08:07:14Z")

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Hi everyone, I wanted to connect a dynamic library compiled by Intel ifort to Julia. The compilation part was no problem. I ran $ ifort -shared -fPIC tt.f90 -o tt.so and got tt.so. Then I moved it to /usr/lib/. Then …

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## [The test isequal(+0.0,-0.0) returns FALSE](https://discourse.julialang.org/t/the-test-isequal-0-0-0-0-returns-false/38404)

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**Author:** [@Lian\_Yunlong](https://discourse.julialang.org/u/Lian_Yunlong)\
**Replies:** 16\
**Last updated:** [June 2, 2020, 7:31am UTC](https://discourse.julialang.org/t/the-test-isequal-0-0-0-0-returns-false/38404 "2020-06-02T07:31:09Z")

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so as isequal(+0.0im,-0.0im). I discovered this during a painful debug process. I really want to understand the philosophy behind this designing, and I wish to get some advice on numerical stability. Thank you @everyon…

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## [Sample rate conversion from audio files](https://discourse.julialang.org/t/sample-rate-conversion-from-audio-files/40578)

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**Author:** [@bafonso](https://discourse.julialang.org/u/bafonso)\
**Replies:** 3\
**Last updated:** [June 2, 2020, 7:25am UTC](https://discourse.julialang.org/t/sample-rate-conversion-from-audio-files/40578 "2020-06-02T07:25:04Z")

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What is the easiest way to load and convert audio files? I’d rather do it on the fly instead of loading and saving as a batch. Right now I am loading files with load or loadstreaming but I need to have a uniform sampling…

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## [When does macro expansion take place/use macro inside hot loop?](https://discourse.julialang.org/t/when-does-macro-expansion-take-place-use-macro-inside-hot-loop/40586)

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**Author:** [@Egwene\_al\_Vere](https://discourse.julialang.org/u/Egwene_al_Vere)\
**Replies:** 2\
**Last updated:** [June 2, 2020, 6:33am UTC](https://discourse.julialang.org/t/when-does-macro-expansion-take-place-use-macro-inside-hot-loop/40586 "2020-06-02T06:33:15Z")

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I have a function inside a nested loop, and I’m cleaning it up with @unpack from UnPack.jl for about 20 parametrs/pre-allocated matrix: @unpack a,b,c = p #parameters... @unpack m1,m2,m3 = p #pre-allocated matrices for t…

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## [\[DataFrames Question\]: Transpose of dataframe](https://discourse.julialang.org/t/dataframes-question-transpose-of-dataframe/28524)

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**Author:** [@Patrick\_Mineault](https://discourse.julialang.org/u/Patrick_Mineault)\
**Replies:** 2\
**Last updated:** [June 2, 2020, 2:41am UTC](https://discourse.julialang.org/t/dataframes-question-transpose-of-dataframe/28524 "2020-06-02T02:41:27Z")

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Question: How do I transpose a dataframe (columns become rows, rows become columns)?

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## [Performance issues with constructors for arbitrary types](https://discourse.julialang.org/t/performance-issues-with-constructors-for-arbitrary-types/40590)

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**Author:** [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Replies:** 4\
**Last updated:** [June 1, 2020, 11:24pm UTC](https://discourse.julialang.org/t/performance-issues-with-constructors-for-arbitrary-types/40590 "2020-06-01T23:24:11Z")

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Hello all. I’ve been struggling now for a good while with a performance issue that seems it should be quite trivial to resolve, but so far, an elegant solution has eluded me. So, I have an object t::Table{T} which lazi…

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## [How do I use multithreaded BLAS in each MPI process](https://discourse.julialang.org/t/how-do-i-use-multithreaded-blas-in-each-mpi-process/40587)

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**Author:** [@shipengcheng1230](https://discourse.julialang.org/u/shipengcheng1230)\
**Replies:** 0\
**Last updated:** [June 1, 2020, 10:38pm UTC](https://discourse.julialang.org/t/how-do-i-use-multithreaded-blas-in-each-mpi-process/40587 "2020-06-01T22:38:25Z")

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I would like to launch one MPI process on each node and perform multithreaded BLAS, the same as tested here, and discussed at combining-distributed-computing-multithreading. Specifically, I am trying to use Elemental.jl:…

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