# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1461

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

**Page:** 1462

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## [Plots with a secondary, non-linear, axis scale](https://discourse.julialang.org/t/plots-with-a-secondary-non-linear-axis-scale/56661)

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**Author:** [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)\
**Replies:** 3\
**Last updated:** [March 13, 2021, 5:21pm UTC](https://discourse.julialang.org/t/plots-with-a-secondary-non-linear-axis-scale/56661 "2021-03-13T17:21:01Z")

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Based on this stack overflow post, a non-linear invertible function can be used to define a secondary PyPlot axis scale. Two questions, if you will: (1) Is it possible to do this with other plot backends? (2) If inst…

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## [How can I include a simple point on my graph using Plots.jl?](https://discourse.julialang.org/t/how-can-i-include-a-simple-point-on-my-graph-using-plots-jl/57058)

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**Author:** [@BridgeBot](https://discourse.julialang.org/u/BridgeBot)\
**Replies:** 1\
**Last updated:** [March 13, 2021, 4:33pm UTC](https://discourse.julialang.org/t/how-can-i-include-a-simple-point-on-my-graph-using-plots-jl/57058 "2021-03-13T16:33:39Z")

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How can I include a simple point on my graph using Plots.jl? Note that the original poster on Slack cannot see your response here on Discourse. Consider transcribing the appropriate answer back to Slack, or pinging the …

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## [Modifying ticks LScene (x,y,z) axis, Makie](https://discourse.julialang.org/t/modifying-ticks-lscene-x-y-z-axis-makie/57079)

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**Author:** [@lazarusA](https://discourse.julialang.org/u/lazarusA)\
**Replies:** 2\
**Last updated:** [March 13, 2021, 3:41pm UTC](https://discourse.julialang.org/t/modifying-ticks-lscene-x-y-z-axis-makie/57079 "2021-03-13T15:41:19Z")

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Hello, does anyone knows a quick way to modified the ticks in 3D plot? the following options don’t seem to work. axis = ax.scene\[OldAxis\] axis\[:xticks\] = (-1:1:1, \["start", "middle", "end"\]) axis\[:ticks\]\[:ranges\_label…

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## [Categorical heatmap](https://discourse.julialang.org/t/categorical-heatmap/56931)

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**Author:** [@jzr](https://discourse.julialang.org/u/jzr)\
**Replies:** 4\
**Last updated:** [March 12, 2021, 11:19am UTC](https://discourse.julialang.org/t/categorical-heatmap/56931 "2021-03-12T11:19:58Z")

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Can I use AoG for a categorical heatmap? using RDatasets let diamonds = dataset("ggplot2", "diamonds") p = data(diamonds) \* mapping(:Cut =\> categorical, :Color =\> categorical, color=:Price) \* visual(Heatmap) draw(…

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## [A cancellable async loop?](https://discourse.julialang.org/t/a-cancellable-async-loop/57068)

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**Author:** [@danvenn](https://discourse.julialang.org/u/danvenn)\
**Replies:** 2\
**Last updated:** [March 13, 2021, 1:43pm UTC](https://discourse.julialang.org/t/a-cancellable-async-loop/57068 "2021-03-13T13:43:58Z")

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Hi - I’d like to be able to send a ‘cancel’ command to an async loop that runs in the background and fetches data. It’s not clear from the docs how I might do that - is this possible using channels?

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## [Trouble with Debugger.@bp](https://discourse.julialang.org/t/trouble-with-debugger-bp/57069)

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**Author:** [@marty0801](https://discourse.julialang.org/u/marty0801)\
**Replies:** 0\
**Last updated:** [March 13, 2021, 12:11pm UTC](https://discourse.julialang.org/t/trouble-with-debugger-bp/57069 "2021-03-13T12:11:39Z")

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I can’t seem to get @bp to catch when used in a module that’s part of a package. I have: module ToyModule import Debugger function f(x) @bp return x^2 end end in a package called Cluster. In a new REP…

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## [A more powerful version of the operator |\>](https://discourse.julialang.org/t/a-more-powerful-version-of-the-operator/57064)

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**Author:** [@anon74562486](https://discourse.julialang.org/u/anon74562486)\
**Replies:** 2\
**Last updated:** [March 13, 2021, 11:19am UTC](https://discourse.julialang.org/t/a-more-powerful-version-of-the-operator/57064 "2021-03-13T11:19:42Z")

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(This is probably the best section to make this proposal) I recently asked a question about how often the |\> operator is used. Many people don’t use the pipe operator because of its limitations (having to write a lambd…

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## [Sorting a sparse axis array](https://discourse.julialang.org/t/sorting-a-sparse-axis-array/57067)

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**Author:** [@priod](https://discourse.julialang.org/u/priod)\
**Replies:** 0\
**Last updated:** [March 13, 2021, 11:00am UTC](https://discourse.julialang.org/t/sorting-a-sparse-axis-array/57067 "2021-03-13T11:00:00Z")

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Hi, I am using the JuMP model, after the optimization process, I have a sparse axis array, I need to sort this array in the descending direction. How can I sort this? Thanking you in advance for the suggestions. The i…

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## [Parse string to color](https://discourse.julialang.org/t/parse-string-to-color/56934)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 4\
**Last updated:** [March 13, 2021, 9:36am UTC](https://discourse.julialang.org/t/parse-string-to-color/56934 "2021-03-13T09:36:18Z")

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Say I have a string "HSV(204,0.7,0.7)", how can I parse it to an instance of one of the ColorTypes types? MWE (I’m looking for function f): julia\> txt = "HSV(204,0.7,0.7)" "HSV(204,0.7,0.7)" julia\> f(txt) == HSV{Float…

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## [How to extract flattened path data from SVG file](https://discourse.julialang.org/t/how-to-extract-flattened-path-data-from-svg-file/57027)

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**Author:** [@arnief3](https://discourse.julialang.org/u/arnief3)\
**Replies:** 5\
**Last updated:** [March 13, 2021, 9:11am UTC](https://discourse.julialang.org/t/how-to-extract-flattened-path-data-from-svg-file/57027 "2021-03-13T09:11:11Z")

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I have used the python library svgpathtools to accomplish this task in the past. Can anyone recommend a way to accomplish this in Julia or am I better off using svgpathtools via PyCall? I have been looking into Cairo.jl…

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## [WebIO error and confusion about Jupyter installation](https://discourse.julialang.org/t/webio-error-and-confusion-about-jupyter-installation/48672)

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**Author:** [@akahs](https://discourse.julialang.org/u/akahs)\
**Replies:** 1\
**Last updated:** [March 13, 2021, 7:08am UTC](https://discourse.julialang.org/t/webio-error-and-confusion-about-jupyter-installation/48672 "2021-03-13T07:08:42Z")

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I am a new user of Julia (v1.5.0) on JupyterLab (v2.2.8). I installed Jupyter via pip (but somehow there also seems to be an installation from conda). Recently I encountered this “WebIO not detected” error when using Plo…

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## [Parallelizing multiple Crank–Nicolson solvers](https://discourse.julialang.org/t/parallelizing-multiple-crank-nicolson-solvers/56861)

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**Author:** [@jagot](https://discourse.julialang.org/u/jagot)\
**Replies:** 21\
**Last updated:** [March 13, 2021, 5:26am UTC](https://discourse.julialang.org/t/parallelizing-multiple-crank-nicolson-solvers/56861 "2021-03-13T05:26:41Z")

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Problem I’m trying to parallelize my time propagator and not seeing very encouraging results. A simple part is where I exponentiate a lot of independent operators using Crank–Nicolson: b\_i = \\exp(-\\mathrm{i}\\delta t h…

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## [Why are some primitive types defined in Julia, and others in the C code?](https://discourse.julialang.org/t/why-are-some-primitive-types-defined-in-julia-and-others-in-the-c-code/57038)

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**Author:** [@nsajko](https://discourse.julialang.org/u/nsajko)\
**Replies:** 1\
**Last updated:** [March 12, 2021, 8:42pm UTC](https://discourse.julialang.org/t/why-are-some-primitive-types-defined-in-julia-and-others-in-the-c-code/57038 "2021-03-12T20:42:46Z")

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Hello, I noticed that the Base Julia code defines some primitive types, but not others, and I’m curious if somebody could explain this. Specifically it seems that Bool, UInt8, Int32, UInt32, Int64, and UInt64 are define…

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## [Overhead of \`Threads.@threads\`](https://discourse.julialang.org/t/overhead-of-threads-threads/53964)

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**Author:** [@ranocha](https://discourse.julialang.org/u/ranocha)\
**Replies:** 30\
**Last updated:** [March 13, 2021, 4:01am UTC](https://discourse.julialang.org/t/overhead-of-threads-threads/53964 "2021-03-13T04:01:17Z")

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There is a certain overhead of using \`Threads.@threads\` even if only a single threads is used.For example, running Julia v1.5.3 with julia --threads=1 yields julia\> using BenchmarkTools julia\> function foo\_serial…

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## ["Considera Julia", 20 min Julia pitch in Spanish](https://discourse.julialang.org/t/considera-julia-20-min-julia-pitch-in-spanish/56990)

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**Author:** [@miguelraz](https://discourse.julialang.org/u/miguelraz)\
**Replies:** 3\
**Last updated:** [March 13, 2021, 2:24am UTC](https://discourse.julialang.org/t/considera-julia-20-min-julia-pitch-in-spanish/56990 "2021-03-13T02:24:36Z")

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Hello all! ¡Saludos banda! I will be giving a brief 20 min-ish talk tomorrow in Spanish called “Considering Julia”. It will be in Spanish, the link is below. I will be pre-recording a longer version (á la JuliaCon) so …

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## [Do any options for fuzzing users' Julia code exist?](https://discourse.julialang.org/t/do-any-options-for-fuzzing-users-julia-code-exist/57048)

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**Author:** [@nsajko](https://discourse.julialang.org/u/nsajko)\
**Replies:** 2\
**Last updated:** [March 13, 2021, 2:22am UTC](https://discourse.julialang.org/t/do-any-options-for-fuzzing-users-julia-code-exist/57048 "2021-03-13T02:22:19Z")

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One of the truly great advantages of writing C or C++ code is the (multiple) possibilities for subjecting that code to fuzz testing, which is an outstanding way to find bugs in code: https://llvm.org/docs/LibFuzzer.html …

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## [How do i give a type signature to julia's help mode? \`?(::String, ::String)\` gives](https://discourse.julialang.org/t/how-do-i-give-a-type-signature-to-julias-help-mode-string-string-gives/57047)

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**Author:** [@BridgeBot](https://discourse.julialang.org/u/BridgeBot)\
**Replies:** 2\
**Last updated:** [March 12, 2021, 11:41pm UTC](https://discourse.julialang.org/t/how-do-i-give-a-type-signature-to-julias-help-mode-string-string-gives/57047 "2021-03-12T23:41:29Z")

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how do i give a type signature to julia’s help mode? ?(::String, ::String) gives something like \* or ::Intand get back every function where ::Int shows up as an argument. For stuff like Any it would be absurd, i think i…

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## [Reapply groupby on a GroupedDataFrame](https://discourse.julialang.org/t/reapply-groupby-on-a-groupeddataframe/57046)

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**Author:** [@jeremiedb](https://discourse.julialang.org/u/jeremiedb)\
**Replies:** 2\
**Last updated:** [March 12, 2021, 10:39pm UTC](https://discourse.julialang.org/t/reapply-groupby-on-a-groupeddataframe/57046 "2021-03-12T22:39:30Z")

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Is there a reason for groupby not supporting a GroupedDataFrame as an input? In a use case, if I try to apply a transform base on different groups, it will hit an error: dfg = groupby(df, "eid") transform!(dfg, "amount…

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## [Incorrect (implicit) gradients for a custom model in Flux](https://discourse.julialang.org/t/incorrect-implicit-gradients-for-a-custom-model-in-flux/56902)

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**Author:** [@arlk](https://discourse.julialang.org/u/arlk)\
**Replies:** 3\
**Last updated:** [March 12, 2021, 10:28pm UTC](https://discourse.julialang.org/t/incorrect-implicit-gradients-for-a-custom-model-in-flux/56902 "2021-03-12T22:28:53Z")

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I’m seeing incorrectly computed gradients when I use a vector of matrices as a model in Flux. The implicit gradients compute to 0 but the structural gradients seem to be computed correctly. MWE: using Flux struct Veco…

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## [How to use heatmap(values)?](https://discourse.julialang.org/t/how-to-use-heatmap-values/57043)

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**Author:** [@jzr](https://discourse.julialang.org/u/jzr)\
**Replies:** 1\
**Last updated:** [March 12, 2021, 8:36pm UTC](https://discourse.julialang.org/t/how-to-use-heatmap-values/57043 "2021-03-12T20:36:21Z")

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heatmap has a heatmap(values) function but there isn’t an example for it in the docs. How can I use it?

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## [Julia's DifferentialEquations package fails when using fortran-wrapped right-hand-side](https://discourse.julialang.org/t/julias-differentialequations-package-fails-when-using-fortran-wrapped-right-hand-side/56995)

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**Author:** [@Nicholaswogan](https://discourse.julialang.org/u/Nicholaswogan)\
**Replies:** 8\
**Last updated:** [March 12, 2021, 8:28pm UTC](https://discourse.julialang.org/t/julias-differentialequations-package-fails-when-using-fortran-wrapped-right-hand-side/56995 "2021-03-12T20:28:28Z")

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I’m trying to solve a system of ordinary differential equations with Julia’s DifferentialEquations method. The right-hand-side of my ODEs is wrapped Fortran 90. Here is my Julia code: using DifferentialEquations functio…

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## [How to append a single row to an Excel file using XLSX?](https://discourse.julialang.org/t/how-to-append-a-single-row-to-an-excel-file-using-xlsx/56203)

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**Author:** [@Michael\_Barmann](https://discourse.julialang.org/u/Michael_Barmann)\
**Replies:** 8\
**Last updated:** [March 12, 2021, 7:17pm UTC](https://discourse.julialang.org/t/how-to-append-a-single-row-to-an-excel-file-using-xlsx/56203 "2021-03-12T19:17:58Z")

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I’m trying to write a simple function that appends a row to an existing Excel spreadsheet. The new row should be appended to the “bottom” of the data in the spreadsheet. I’m assuming that if there are existing rows in t…

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## [Getting Oriented](https://discourse.julialang.org/t/getting-oriented/56970)

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**Author:** [@Ross\_Boylan](https://discourse.julialang.org/u/Ross_Boylan)\
**Replies:** 6\
**Last updated:** [March 12, 2021, 7:09pm UTC](https://discourse.julialang.org/t/getting-oriented/56970 "2021-03-12T19:09:11Z")

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The introduction to the optimization topic in discourse refers to http://www.juliaopt.org/, but that site declares itself to be dead and obsolete, while referencing https://jump.dev/. But the latter does not appear to b…

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## [Makie: New Figure w/ multiple LScenes auto-resizing when undesired](https://discourse.julialang.org/t/makie-new-figure-w-multiple-lscenes-auto-resizing-when-undesired/56975)

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**Author:** [@zobot](https://discourse.julialang.org/u/zobot)\
**Replies:** 6\
**Last updated:** [March 12, 2021, 6:44pm UTC](https://discourse.julialang.org/t/makie-new-figure-w-multiple-lscenes-auto-resizing-when-undesired/56975 "2021-03-12T18:44:43Z")

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Hi, I’m trying to learn the new Figure system to combine animated LScenes with contour plots. I generate a curve for the camera eyepos and lookat and values for the plots for each frame. I’ve figured out all of that but …

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## ["could not load library" problem from inside Juno](https://discourse.julialang.org/t/could-not-load-library-problem-from-inside-juno/37128)

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**Author:** [@nshaviv](https://discourse.julialang.org/u/nshaviv)\
**Replies:** 6\
**Last updated:** [March 12, 2021, 6:33pm UTC](https://discourse.julialang.org/t/could-not-load-library-problem-from-inside-juno/37128 "2021-03-12T18:33:06Z")

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I am an enthusiastic julia newbie. I was trying to run ArrayFire (i.e., use the GPU with Julia). After downloading and installing ArrayFire and ArrayFire.jl, it worked in Julia running from the command line, but not thro…

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## [Nicer parameter indexing](https://discourse.julialang.org/t/nicer-parameter-indexing/50704)

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**Author:** [@ohmsweetohm1](https://discourse.julialang.org/u/ohmsweetohm1)\
**Replies:** 3\
**Last updated:** [March 12, 2021, 5:21pm UTC](https://discourse.julialang.org/t/nicer-parameter-indexing/50704 "2021-03-12T17:21:29Z")

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Consider the following example: import Plots using ModelingToolkit, DifferentialEquations @parameters t σ ρ β @variables x(t) y(t) z(t) @derivatives D'~t eqs = \[D(x) ~ σ \* (y - x), D(y) ~ x \* (ρ - z) - y, …

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## [Implications of --compile=min and --optimize=0, for dummies](https://discourse.julialang.org/t/implications-of-compile-min-and-optimize-0-for-dummies/56894)

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**Author:** [@kevbonham](https://discourse.julialang.org/u/kevbonham)\
**Replies:** 22\
**Last updated:** [March 12, 2021, 4:40pm UTC](https://discourse.julialang.org/t/implications-of-compile-min-and-optimize-0-for-dummies/56894 "2021-03-12T16:40:42Z")

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I’m starting to build some command line interfaces for some projects, and trying to figure out the best practices. In Fredrik Ekre’s juliacon talk, he recommends one option is to use --compile=min --optimize=0, but I’m t…

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## [When I am developing a package or entering in dev environment using\`dev package\_n](https://discourse.julialang.org/t/when-i-am-developing-a-package-or-entering-in-dev-environment-using-dev-package-n/57019)

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**Author:** [@BridgeBot](https://discourse.julialang.org/u/BridgeBot)\
**Replies:** 1\
**Last updated:** [March 12, 2021, 4:09pm UTC](https://discourse.julialang.org/t/when-i-am-developing-a-package-or-entering-in-dev-environment-using-dev-package-n/57019 "2021-03-12T16:09:49Z")

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When I am developing a package or entering in dev environment using dev package\_name I am getting the following error: ERROR: The following package names could not be resolved: \* package\_name (not found in project, m…

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## [Indexible structures like Matlab?](https://discourse.julialang.org/t/indexible-structures-like-matlab/56923)

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**Author:** [@bionicinnovations1](https://discourse.julialang.org/u/bionicinnovations1)\
**Replies:** 12\
**Last updated:** [March 12, 2021, 4:08pm UTC](https://discourse.julialang.org/t/indexible-structures-like-matlab/56923 "2021-03-12T16:08:46Z")

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I am trying to generate bunch of matrices or vectors, but the number I need varies. In Matlab, I could do something like this: for k = 1:5 X(k).A = rand(2,2) X(k).B = rand(1,1) X(k).C = rand(2,3) end which would gene…

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## [Assigning a null value to a variable](https://discourse.julialang.org/t/assigning-a-null-value-to-a-variable/56988)

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**Author:** [@Peter-Jolly](https://discourse.julialang.org/u/Peter-Jolly)\
**Replies:** 13\
**Last updated:** [March 12, 2021, 3:44pm UTC](https://discourse.julialang.org/t/assigning-a-null-value-to-a-variable/56988 "2021-03-12T15:44:09Z")

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Hi, I am trying to write a variable x to a matrix, that is output ultimately as a CSV file. Sometimes x will have a numerical value and other time no value (a null in my old language VBA). The question is how to assign…

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