# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=404

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**Page:** 405

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## [Julia Notable Uses](https://discourse.julialang.org/t/julia-notable-uses/86130)

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**Author:** [@Freya\_the\_Goddess](https://discourse.julialang.org/u/Freya_the_Goddess)\
**Replies:** 12\
**Last updated:** [August 27, 2022, 2:40pm UTC](https://discourse.julialang.org/t/julia-notable-uses/86130 "2022-08-27T14:40:46Z")

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Hi all, it is the good motivation for anyone who want to learn Julia. I read from wikipedia: Julia is used by NASA, e.g. for modeling spacecraft separation dynamics (15,000 times faster than before with Simulink/MATLAB…

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## [Meaning of "..." in plot(f, extrema(xs)...)](https://discourse.julialang.org/t/meaning-of-in-plot-f-extrema-xs/86427)

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**Author:** [@rsimic](https://discourse.julialang.org/u/rsimic)\
**Replies:** 1\
**Last updated:** [August 27, 2022, 12:04pm UTC](https://discourse.julialang.org/t/meaning-of-in-plot-f-extrema-xs/86427 "2022-08-27T12:04:56Z")

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what does it mean 3 dots (…) after vector, example extrema(\[1, 2, 3\])…

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## [Array promotion: too eager?](https://discourse.julialang.org/t/array-promotion-too-eager/86422)

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**Author:** [@aplavin](https://discourse.julialang.org/u/aplavin)\
**Replies:** 1\
**Last updated:** [August 27, 2022, 9:05am UTC](https://discourse.julialang.org/t/array-promotion-too-eager/86422 "2022-08-27T09:05:02Z")

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I’ve noticed that recent 1.9 nightlies became more eager in converting array elements to a common type. This seems unambiguously breaking, and not sure about the motivation: what were the reasons for such a change? For …

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## [Differences between table types](https://discourse.julialang.org/t/differences-between-table-types/86409)

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**Author:** [@Jake](https://discourse.julialang.org/u/Jake)\
**Replies:** 1\
**Last updated:** [August 27, 2022, 3:05am UTC](https://discourse.julialang.org/t/differences-between-table-types/86409 "2022-08-27T03:05:40Z")

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I am creating a package. Within it I will have tabular information. For an analysis there will be item specific information stored in tabular form. Based on the item the specific row from the table will need to be mat…

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## [Why is missing defined as singleton](https://discourse.julialang.org/t/why-is-missing-defined-as-singleton/32561)

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**Author:** [@jandehaan](https://discourse.julialang.org/u/jandehaan)\
**Replies:** 14\
**Last updated:** [August 26, 2022, 9:06pm UTC](https://discourse.julialang.org/t/why-is-missing-defined-as-singleton/32561 "2022-08-26T21:06:01Z")

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Currently type Missing is defined as struct Missing end and the singleton instance of that type is defined as const missing = Missing() But what if we defined the following: struct Missing why::Int end Missing() =…

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## [Mutating a dictionary through aliases](https://discourse.julialang.org/t/mutating-a-dictionary-through-aliases/86378)

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**Author:** [@danielsoutar](https://discourse.julialang.org/u/danielsoutar)\
**Replies:** 4\
**Last updated:** [August 26, 2022, 8:40pm UTC](https://discourse.julialang.org/t/mutating-a-dictionary-through-aliases/86378 "2022-08-26T20:40:28Z")

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Let’s say I have a dictionary like so: my\_object = Dict{Symbol, Any}( :foo =\> Dict{Symbol, Any}( :foo\_items =\> \["item\_a", "item\_b", "item\_c"\], :bar =\> Dict{Symbol, Any}( :bar\_name =\> \["na…

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## [Create Interval Notation in Julia?](https://discourse.julialang.org/t/create-interval-notation-in-julia/86375)

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**Author:** [@Freya\_the\_Goddess](https://discourse.julialang.org/u/Freya_the_Goddess)\
**Replies:** 2\
**Last updated:** [August 26, 2022, 10:00am UTC](https://discourse.julialang.org/t/create-interval-notation-in-julia/86375 "2022-08-26T10:00:55Z")

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Hi all, I wonder about creating interval notation using Intervals package, if there is any package that is able do tell me. I try it this way: using Plots, LaTeXStrings, Intervals a = Interval{Closed, Closed}(1, 10) …

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## [API for location of cov files with \`Pkg.test(; coverage = true)](https://discourse.julialang.org/t/api-for-location-of-cov-files-with-pkg-test-coverage-true/86087)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 2\
**Last updated:** [August 26, 2022, 9:35am UTC](https://discourse.julialang.org/t/api-for-location-of-cov-files-with-pkg-test-coverage-true/86087 "2022-08-26T09:35:08Z")

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Suppose a user activated a project and then called import Pkg Pkg.test(; coverage = true) What would be the API for returning the location of the cov files (eg an src directory). (I need this for LocalCoverage.jl). Re…

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## [Unitful.jl | possibly mislabelled AbstractTypes, rare sametype() error | new user observations](https://discourse.julialang.org/t/unitful-jl-possibly-mislabelled-abstracttypes-rare-sametype-error-new-user-observations/86017)

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**Author:** [@jlawrie](https://discourse.julialang.org/u/jlawrie)\
**Replies:** 2\
**Last updated:** [August 26, 2022, 8:02am UTC](https://discourse.julialang.org/t/unitful-jl-possibly-mislabelled-abstracttypes-rare-sametype-error-new-user-observations/86017 "2022-08-26T08:02:19Z")

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Hello everyone; I have been getting the hang of the very nice Unitful.jl package recently. I really like it, and would like to take the chance to thank those in the community who develop(ed) and maintain(ed) this packag…

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## [How to give someone your code to run](https://discourse.julialang.org/t/how-to-give-someone-your-code-to-run/86357)

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**Author:** [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)\
**Replies:** 2\
**Last updated:** [August 25, 2022, 11:52pm UTC](https://discourse.julialang.org/t/how-to-give-someone-your-code-to-run/86357 "2022-08-25T23:52:14Z")

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Perhaps this deserves a thread of its own. Here is a really simple solution to the problem how to give someone your code to run. Visit GitHub - PetrKryslUCSD/FreeVibrationExample: Simple Example of Free Vibration Comput…

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## [How to continuously communicate with an external program?](https://discourse.julialang.org/t/how-to-continuously-communicate-with-an-external-program/86319)

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**Author:** [@ArthurW](https://discourse.julialang.org/u/ArthurW)\
**Replies:** 5\
**Last updated:** [August 25, 2022, 11:48pm UTC](https://discourse.julialang.org/t/how-to-continuously-communicate-with-an-external-program/86319 "2022-08-25T23:48:09Z")

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Hi. I’m trying to write to the stdin of an external program and read from it’s stdout multiple times while it’s still executing. For example, consider this C code that indefinetly reads an integer input a and outputs a+…

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## [Package for financial calculator type functions?](https://discourse.julialang.org/t/package-for-financial-calculator-type-functions/86361)

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**Author:** [@dlakelan](https://discourse.julialang.org/u/dlakelan)\
**Replies:** 2\
**Last updated:** [August 25, 2022, 10:35pm UTC](https://discourse.julialang.org/t/package-for-financial-calculator-type-functions/86361 "2022-08-25T22:35:38Z")

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Suppose you want to do the kinds of things excel will do for simple financial calculations, like net present value, internal rate of return, mortgage tables, blablabla but in Julia? Is there a package that does these thi…

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## [How to customize broadcast for a function that accepts keyword arguments?](https://discourse.julialang.org/t/how-to-customize-broadcast-for-a-function-that-accepts-keyword-arguments/86351)

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**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 0\
**Last updated:** [August 25, 2022, 5:28pm UTC](https://discourse.julialang.org/t/how-to-customize-broadcast-for-a-function-that-accepts-keyword-arguments/86351 "2022-08-25T17:28:47Z")

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Suppose I have a function julia\> function f(n::Int) @assert n \> 0 n == 1 && return 1 f(n-1) + 1 end and another function to cache the values of f(n) for a range of n: julia\> cac…

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## [Some way to debug syntax errors?](https://discourse.julialang.org/t/some-way-to-debug-syntax-errors/86336)

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**Author:** [@nsajko](https://discourse.julialang.org/u/nsajko)\
**Replies:** 1\
**Last updated:** [August 25, 2022, 5:12pm UTC](https://discourse.julialang.org/t/some-way-to-debug-syntax-errors/86336 "2022-08-25T17:12:46Z")

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I’ve got a syntax error in my code (in a function in a module) and I can’t seem to figure it out. The expression goes something like this: ntuple( let a = b i -\> expr(a, i) end, Val{c}()) According to the err…

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## [Display of \`Array{Union{Bool,Missing},N}\` vs Array{Bool,N}\`](https://discourse.julialang.org/t/display-of-array-union-bool-missing-n-vs-array-bool-n/86332)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 0\
**Last updated:** [August 25, 2022, 3:06pm UTC](https://discourse.julialang.org/t/display-of-array-union-bool-missing-n-vs-array-bool-n/86332 "2022-08-25T15:06:45Z")

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Isn’t it a bit annoying that the display of an Array{Union{Bool,Missing},N} uses different conventions than than the display of an Array{Bool,N} ? julia\> x = \[false,true\] 2-element Vector{Bool}: 0 1 julia\> y = \[false…

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## [Best way to have GC manage freeing C-allocated storage](https://discourse.julialang.org/t/best-way-to-have-gc-manage-freeing-c-allocated-storage/86233)

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**Author:** [@jlapeyre](https://discourse.julialang.org/u/jlapeyre)\
**Replies:** 8\
**Last updated:** [August 25, 2022, 3:35am UTC](https://discourse.julialang.org/t/best-way-to-have-gc-manage-freeing-c-allocated-storage/86233 "2022-08-25T03:35:33Z")

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What is the best (or a good) way of solving the following very generic problem? I’d like to call obj\_alloc() and obj\_free() in some C library from Julia. On the Julia side, work with Ptr{obj}. It can be considered opaq…

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## [Optimization of checking on conditions in a 3d array](https://discourse.julialang.org/t/optimization-of-checking-on-conditions-in-a-3d-array/86282)

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**Author:** [@Sergey\_Novak](https://discourse.julialang.org/u/Sergey_Novak)\
**Replies:** 13\
**Last updated:** [August 25, 2022, 12:17pm UTC](https://discourse.julialang.org/t/optimization-of-checking-on-conditions-in-a-3d-array/86282 "2022-08-25T12:17:44Z")

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I have an example of a python code snippet. I need to check all the numbers from the map\_spectrum array for 5 conditions, then put the new value in another array according to them. How can this be done in a more optimize…

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## [DataDrivenDiffEq.jl sparse regression](https://discourse.julialang.org/t/datadrivendiffeq-jl-sparse-regression/86312)

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**Author:** [@yewalenikhil65](https://discourse.julialang.org/u/yewalenikhil65)\
**Replies:** 2\
**Last updated:** [August 25, 2022, 11:43am UTC](https://discourse.julialang.org/t/datadrivendiffeq-jl-sparse-regression/86312 "2022-08-25T11:43:19Z")

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Regarding DataDrivenDiffEq.jl I have precalculated estimate of candidate\_matrix and also Derivative matrix… How do i use sparse regression to solve for sparse coefficient matrix ?? solve on SINDy assumes basis in symboli…

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## [No real multithreading possible?](https://discourse.julialang.org/t/no-real-multithreading-possible/77920)

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**Author:** [@agcm](https://discourse.julialang.org/u/agcm)\
**Replies:** 8\
**Last updated:** [August 25, 2022, 9:20am UTC](https://discourse.julialang.org/t/no-real-multithreading-possible/77920 "2022-08-25T09:20:54Z")

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Hey there, I am desperately trying to figure out how to do some “real” multi-threadding in Julia. What do I mean by that: My program consists of three tasks: the main task and two separate task I start. I need to commun…

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## [JupyterLab Plotting Problem](https://discourse.julialang.org/t/jupyterlab-plotting-problem/86302)

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**Author:** [@Freya\_the\_Goddess](https://discourse.julialang.org/u/Freya_the_Goddess)\
**Replies:** 2\
**Last updated:** [August 25, 2022, 8:24am UTC](https://discourse.julialang.org/t/jupyterlab-plotting-problem/86302 "2022-08-25T08:24:32Z")

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Hi all, I have been trying to plot and compare the result in: JupyterLab / iJulia Julia REPL I try this code: using Plots, LaTeXStrings, Plots.PlotMeasures gr() f(x) = x^(2) g(x) = x^(4) h(x) = x^(6) plot(f,-10,1…

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## [Is there a way to De-Broadcast?](https://discourse.julialang.org/t/is-there-a-way-to-de-broadcast/86281)

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**Author:** [@compleat](https://discourse.julialang.org/u/compleat)\
**Replies:** 4\
**Last updated:** [August 24, 2022, 9:17pm UTC](https://discourse.julialang.org/t/is-there-a-way-to-de-broadcast/86281 "2022-08-24T21:17:30Z")

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I have come across cases of functions (e.g. the functions in Splines2, and elsewhere) where vectors are required as inputs, and where these same functions fail for scalar input (where conversion to/from 1-dim vector is r…

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## [Assigning to a getter function](https://discourse.julialang.org/t/assigning-to-a-getter-function/86278)

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**Author:** [@StackEnjoyer](https://discourse.julialang.org/u/StackEnjoyer)\
**Replies:** 3\
**Last updated:** [August 24, 2022, 6:09pm UTC](https://discourse.julialang.org/t/assigning-to-a-getter-function/86278 "2022-08-24T18:09:25Z")

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Getter and setter functions Recently I stumbled on some interesting behaviour when using a “getter”-like function in combination with broadcasting calls. For the sake of argument lets assume: abstract type AbstractPoint…

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## [How to free ownership of the memory](https://discourse.julialang.org/t/how-to-free-ownership-of-the-memory/86234)

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**Author:** [@lionisxn](https://discourse.julialang.org/u/lionisxn)\
**Replies:** 11\
**Last updated:** [August 24, 2022, 5:31pm UTC](https://discourse.julialang.org/t/how-to-free-ownership-of-the-memory/86234 "2022-08-24T17:31:28Z")

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In the docs explaining the method of “unsafe\_wrap(Array, pointer::Ptr{T}, dims; own = false)”, It says that “… own optionally specifies whether Julia should take ownership of the memory, calling free on the pointer when …

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## [Vcat broadcast to all columns?](https://discourse.julialang.org/t/vcat-broadcast-to-all-columns/86178)

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**Author:** [@user664303](https://discourse.julialang.org/u/user664303)\
**Replies:** 49\
**Last updated:** [August 24, 2022, 3:32pm UTC](https://discourse.julialang.org/t/vcat-broadcast-to-all-columns/86178 "2022-08-24T15:32:33Z")

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In MATLAB, if I write x(end+1,:) = 1, it will concatenate a row of ones to the bottom of the matrix x. I haven’t found a better way of doing this in Julia than x = vcat(x, ones(typeof(x\[1\]), 1, size(x, 2))). An issue is …

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## [ForwardDiff.jl: ERROR: LoadError: MethodError: no method matching Float64(::ForwardDiff.Dual{ForwardDiff.Tag{Zygote.var"#104#105"{var"#f#1"}, Float64}, Float64, 1})](https://discourse.julialang.org/t/forwarddiff-jl-error-loaderror-methoderror-no-method-matching-float64-forwarddiff-dual-forwarddiff-tag-zygote-var-104-105-var-f-1-float64-float64-1/86175)

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**Author:** [@F-YF](https://discourse.julialang.org/u/F-YF)\
**Replies:** 5\
**Last updated:** [August 24, 2022, 2:34pm UTC](https://discourse.julialang.org/t/forwarddiff-jl-error-loaderror-methoderror-no-method-matching-float64-forwarddiff-dual-forwarddiff-tag-zygote-var-104-105-var-f-1-float64-float64-1/86175 "2022-08-24T14:34:57Z")

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I had a lot of problems with ForwardDiff. I used Zygote to do automatic differential calculations before, so I didn’t know much about ForwardDiff. My original intention was to use Zygote to achieve the gradient of gradie…

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## [Removing the first index along N-1 dimensions of an Array](https://discourse.julialang.org/t/removing-the-first-index-along-n-1-dimensions-of-an-array/86246)

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**Author:** [@Luis\_Calderon](https://discourse.julialang.org/u/Luis_Calderon)\
**Replies:** 2\
**Last updated:** [August 24, 2022, 11:20am UTC](https://discourse.julialang.org/t/removing-the-first-index-along-n-1-dimensions-of-an-array/86246 "2022-08-24T11:20:44Z")

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Dear Julia Community, This is my first time posting, so I hope I meet the standards put in place. Thank you for all of this btw!! Problem: Let me illustrate with an example. For a 3D array, I’d like to remove any compo…

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## [Why isn't getproperty defined for Dictionaries?](https://discourse.julialang.org/t/why-isnt-getproperty-defined-for-dictionaries/85233)

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**Author:** [@Nathan\_Boyer](https://discourse.julialang.org/u/Nathan_Boyer)\
**Replies:** 11\
**Last updated:** [August 24, 2022, 5:35am UTC](https://discourse.julialang.org/t/why-isnt-getproperty-defined-for-dictionaries/85233 "2022-08-24T05:35:29Z")

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It would be convenient to have the ability to retrieve Dict values with dot syntax. Seems like methods could be added to getproperty for Dict{String, \<:Any} and Dict{Symbol, \<:Any} so that values could be accessed the sa…

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## [Make\_subplots(): Two rows, One column](https://discourse.julialang.org/t/make-subplots-two-rows-one-column/86179)

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**Author:** [@ellocco](https://discourse.julialang.org/u/ellocco)\
**Replies:** 5\
**Last updated:** [August 24, 2022, 1:14am UTC](https://discourse.julialang.org/t/make-subplots-two-rows-one-column/86179 "2022-08-24T01:14:42Z")

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Yesterday it gave me an headache, why I can not plot two figures on top of each other, the problem is related to the topic: how-to-create-a-2x1-array. Here is my example: using PlotlyJS hdl\_trace1 = scatter(x=\[1, 2\]…

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## [Is there a way to hide the boxplots names on the x axis?](https://discourse.julialang.org/t/is-there-a-way-to-hide-the-boxplots-names-on-the-x-axis/86223)

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**Author:** [@Juan\_Mac\_Donagh](https://discourse.julialang.org/u/Juan_Mac_Donagh)\
**Replies:** 3\
**Last updated:** [August 24, 2022, 1:09am UTC](https://discourse.julialang.org/t/is-there-a-way-to-hide-the-boxplots-names-on-the-x-axis/86223 "2022-08-24T01:09:00Z")

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Hi, I was wondering if there was a way to hide the names of each boxplots using StatsPlots grouped boxplots. I looked into both Plots and StatsPlots documentation, but I couldn’t find an argument atribute for it. Here’s…

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## [Missing libarpack on Mac M1](https://discourse.julialang.org/t/missing-libarpack-on-mac-m1/86167)

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**Author:** [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)\
**Replies:** 2\
**Last updated:** [August 24, 2022, 12:06am UTC](https://discourse.julialang.org/t/missing-libarpack-on-mac-m1/86167 "2022-08-24T00:06:15Z")

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My friend has a new toy, Mac M1, and wants to run one of the codes that I wrote for him. Arpack is needed for eigs, but the machine chokes on it: missing libarpack. Julia 1.8… Is there a trick, or are we out of luck?

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