# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1615

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

**Page:** 1616

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## [Why might I be seeing a large overhead for multiprocessing?](https://discourse.julialang.org/t/why-might-i-be-seeing-a-large-overhead-for-multiprocessing/47547)

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**Author:** [@JamesK](https://discourse.julialang.org/u/JamesK)\
**Replies:** 8\
**Last updated:** [October 1, 2020, 5:07am UTC](https://discourse.julialang.org/t/why-might-i-be-seeing-a-large-overhead-for-multiprocessing/47547 "2020-10-01T05:07:07Z")

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I have an 8 core machine. When I run a certain piece of code with Python’s multiprocessing.Pool library, with 1 core vs. 4 cores, I see an almost 4x speedup for the 4 core case, with very little overhead penalty, assumi…

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## [Dataframes with groupby in parallel](https://discourse.julialang.org/t/dataframes-with-groupby-in-parallel/47186)

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**Author:** [@bicepjai](https://discourse.julialang.org/u/bicepjai)\
**Replies:** 1\
**Last updated:** [October 1, 2020, 4:39am UTC](https://discourse.julialang.org/t/dataframes-with-groupby-in-parallel/47186 "2020-10-01T04:39:06Z")

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I have a dataframe of size (2450225, 117) Just using pandas and multiprocessing module, gives me the results in 34 seconds. I have panda code below. I am trying to achieve the same with julia and hoping this would be a …

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## [Allocation seem high for such a simple function?](https://discourse.julialang.org/t/allocation-seem-high-for-such-a-simple-function/47565)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 2\
**Last updated:** [October 1, 2020, 3:38am UTC](https://discourse.julialang.org/t/allocation-seem-high-for-such-a-simple-function/47565 "2020-10-01T03:38:18Z")

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minimumby(f, itr) = itr\[argmin(map(f, itr))\] @time minimumby(x-\>x^2, \[-2, 1, 2, 3, 4\]) I get 0.044858 seconds (48.96 k allocations: 2.505 MiB) This is quite slow and a lot of allocations But if I give the function a…

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## [Dataframes: How to conditionally remove rows based on data values?](https://discourse.julialang.org/t/dataframes-how-to-conditionally-remove-rows-based-on-data-values/47538)

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**Author:** [@mike\_k](https://discourse.julialang.org/u/mike_k)\
**Replies:** 4\
**Last updated:** [October 1, 2020, 1:52am UTC](https://discourse.julialang.org/t/dataframes-how-to-conditionally-remove-rows-based-on-data-values/47538 "2020-10-01T01:52:06Z")

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Dear folks, I fail to remove rows in a dataframe based on conditions. Here is an MWE: The dataframe is │ Row │ A │ B │ │ │ String │ String │ ├─────┼────────┼────────┤ │ 1 │ X │ C │ │ 2 │ X …

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## [Plotting curvilinear coordinate function on Cartesian plane](https://discourse.julialang.org/t/plotting-curvilinear-coordinate-function-on-cartesian-plane/47294)

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**Author:** [@kapple](https://discourse.julialang.org/u/kapple)\
**Replies:** 4\
**Last updated:** [September 30, 2020, 11:54pm UTC](https://discourse.julialang.org/t/plotting-curvilinear-coordinate-function-on-cartesian-plane/47294 "2020-09-30T23:54:08Z")

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Suppose I have the following curvilinear coordinate (s, n) transform to Cartesian coordinates (x, y, z) x = f(s, n) \\\\ y = g(s, n) \\\\ z = h(s, n) where f(s, n), g(s, n), and h(s, n) are inaccessible functions (i.e. th…

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## [How to debug compiler hang?](https://discourse.julialang.org/t/how-to-debug-compiler-hang/47559)

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**Author:** [@marius311](https://discourse.julialang.org/u/marius311)\
**Replies:** 0\
**Last updated:** [September 30, 2020, 11:23pm UTC](https://discourse.julialang.org/t/how-to-debug-compiler-hang/47559 "2020-09-30T23:23:30Z")

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I’ve got a piece of long-running code which runs for about 5min, then, on what seems like a totally benign command, hangs for like 10minutes, every time. It does eventually complete and continue running after that. I thi…

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## [Flux model with categorical and continuous covariates/features](https://discourse.julialang.org/t/flux-model-with-categorical-and-continuous-covariates-features/47556)

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**Author:** [@johnbb](https://discourse.julialang.org/u/johnbb)\
**Replies:** 0\
**Last updated:** [September 30, 2020, 10:49pm UTC](https://discourse.julialang.org/t/flux-model-with-categorical-and-continuous-covariates-features/47556 "2020-09-30T22:49:53Z")

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Using Flux, I would like to train a regression model with both continuous and categorical features. Since the categorical variable(s) may have a many levels, I would prefer to map these into a few new continuous variable…

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## [Handling compatibility requirements for identical packages across two registries](https://discourse.julialang.org/t/handling-compatibility-requirements-for-identical-packages-across-two-registries/47553)

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**Author:** [@Robert\_Moss](https://discourse.julialang.org/u/Robert_Moss)\
**Replies:** 0\
**Last updated:** [September 30, 2020, 9:29pm UTC](https://discourse.julialang.org/t/handling-compatibility-requirements-for-identical-packages-across-two-registries/47553 "2020-09-30T21:29:12Z")

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We’ve been migrating packages in the JuliaPOMDP/Registry over to General and I’ve been experiencing odd overlapping compatibility issues with packages listed in both registries. When adding a package (say MCTS.jl v0.4.6…

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## [Vectorizing observations from multivariate distribution in Turing](https://discourse.julialang.org/t/vectorizing-observations-from-multivariate-distribution-in-turing/47436)

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**Author:** [@ElOceanografo](https://discourse.julialang.org/u/ElOceanografo)\
**Replies:** 1\
**Last updated:** [September 30, 2020, 9:06pm UTC](https://discourse.julialang.org/t/vectorizing-observations-from-multivariate-distribution-in-turing/47436 "2020-09-30T21:06:31Z")

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I have a model where the data are drawn from multinomial distributions. The parameters of those distributions (number of draws and probabilities) are different at each data point. MWE below: ndata = 100 k = 5 n = 10 p…

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## [ANN: Jet.jl - Snippet search](https://discourse.julialang.org/t/ann-jet-jl-snippet-search/47548)

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**Author:** [@abelsiqueira](https://discourse.julialang.org/u/abelsiqueira)\
**Replies:** 2\
**Last updated:** [September 30, 2020, 8:27pm UTC](https://discourse.julialang.org/t/ann-jet-jl-snippet-search/47548 "2020-09-30T20:27:40Z")

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Hello, I started a package that I hope is useful. It is a kind of TLDR for Julia, and I’m calling it Jet.jl for now. It provides a REPL with } (Thanks to ReplMaker.jl) using Jet jet\_repl() } jet\> And so far 2 ways of…

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## [Troubles with gcc 9](https://discourse.julialang.org/t/troubles-with-gcc-9/47550)

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**Author:** [@joa-quim](https://discourse.julialang.org/u/joa-quim)\
**Replies:** 4\
**Last updated:** [September 30, 2020, 7:46pm UTC](https://discourse.julialang.org/t/troubles-with-gcc-9/47550 "2020-09-30T19:46:09Z")

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A GMT user posted an issue that I was able to reproduce in WSL2 + gcc9. The error is ERROR: LoadError: LoadError: could not load library "/home/j/programs/lib/libgmt.so" /home/j/programs/julia/bin/../lib/julia/libstdc++…

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## [Sundials solver options question, is dt ignored(initial step), and is maxorder a viable option? What is the default, 4?](https://discourse.julialang.org/t/sundials-solver-options-question-is-dt-ignored-initial-step-and-is-maxorder-a-viable-option-what-is-the-default-4/47549)

<div class="topic-metadata">

**Author:** [@cbasile21](https://discourse.julialang.org/u/cbasile21)\
**Replies:** 2\
**Last updated:** [September 30, 2020, 7:22pm UTC](https://discourse.julialang.org/t/sundials-solver-options-question-is-dt-ignored-initial-step-and-is-maxorder-a-viable-option-what-is-the-default-4/47549 "2020-09-30T19:22:44Z")

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The solver compatibility chart, says that dt is ignored for sundials, is this correct? I did not see any errors when using it. Moreover, is maxorder a viable option? Is the default for CVODE\_BDF 4 or 5? Can it be changed…

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## [Ipopt and external function](https://discourse.julialang.org/t/ipopt-and-external-function/47496)

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**Author:** [@danicaratelli](https://discourse.julialang.org/u/danicaratelli)\
**Replies:** 11\
**Last updated:** [September 30, 2020, 6:40pm UTC](https://discourse.julialang.org/t/ipopt-and-external-function/47496 "2020-09-30T18:40:17Z")

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I am trying to solve a non-linear function using JuMP. From what I saw, I have to use Ipopt and, as Nonlinear Modeling · JuMP says, I cannot directly include the function in the NLobjective. To get around this I define a…

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## [Finding a vector which has the sum of the indices which are prime numbers](https://discourse.julialang.org/t/finding-a-vector-which-has-the-sum-of-the-indices-which-are-prime-numbers/47492)

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**Author:** [@julianoob](https://discourse.julialang.org/u/julianoob)\
**Replies:** 7\
**Last updated:** [September 30, 2020, 6:28pm UTC](https://discourse.julialang.org/t/finding-a-vector-which-has-the-sum-of-the-indices-which-are-prime-numbers/47492 "2020-09-30T18:28:56Z")

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For example a=\[1 2 3; 4 5 6; 7 8 9\] indices are ((1,1) ,(1,2) , (1,3); (2,1),(2,2),(2,3); (3,1),(3,2),(3,3)) and the prime number of these sums are 2,3,5 which should be in the vector s. Is there any function in julia wh…

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## [Help me figure out where to file this bug?](https://discourse.julialang.org/t/help-me-figure-out-where-to-file-this-bug/47512)

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**Author:** [@dlakelan](https://discourse.julialang.org/u/dlakelan)\
**Replies:** 3\
**Last updated:** [September 30, 2020, 5:07pm UTC](https://discourse.julialang.org/t/help-me-figure-out-where-to-file-this-bug/47512 "2020-09-30T17:07:41Z")

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I’m summarizing some data (that I can’t show you, it’s part of a lawsuit) and I’m running the following command through Query.jl… if I leave out the part uniquen = length(unique(\_.customer\_id)) everything works, but if I…

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## [Most efficient way of computing B'\* inv(A)\* B for A large](https://discourse.julialang.org/t/most-efficient-way-of-computing-b-inv-a-b-for-a-large/47513)

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**Author:** [@Joris\_Pinkse](https://discourse.julialang.org/u/Joris_Pinkse)\
**Replies:** 30\
**Last updated:** [September 30, 2020, 4:19pm UTC](https://discourse.julialang.org/t/most-efficient-way-of-computing-b-inv-a-b-for-a-large/47513 "2020-09-30T16:19:04Z")

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I have a positive definite high-dimensional matrix A and wish to compute B’ \* inv(A) \* B where the result is low-dimensional. What is the fastest way of accomplishing this for generic B?

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## [GraphRecipes (or equivalent) for this series of plots](https://discourse.julialang.org/t/graphrecipes-or-equivalent-for-this-series-of-plots/47544)

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**Author:** [@mkarikom](https://discourse.julialang.org/u/mkarikom)\
**Replies:** 0\
**Last updated:** [September 30, 2020, 4:09pm UTC](https://discourse.julialang.org/t/graphrecipes-or-equivalent-for-this-series-of-plots/47544 "2020-09-30T16:09:44Z")

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I have a directed graph in LightGraphs and I want to produce a series of plots each with the same circular layout but highlighting different subsets of edges, with highlighting on the nodes:

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## [How to interactively refer to other modules' type?](https://discourse.julialang.org/t/how-to-interactively-refer-to-other-modules-type/47540)

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**Author:** [@iHany](https://discourse.julialang.org/u/iHany)\
**Replies:** 2\
**Last updated:** [September 30, 2020, 2:00pm UTC](https://discourse.julialang.org/t/how-to-interactively-refer-to-other-modules-type/47540 "2020-09-30T14:00:01Z")

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I’m confused with interactively referring types across modules. Here’s my example: src/MyModuleA.jl module A using Reexport include("MyModuleB.jl") include("MyModuleC.jl") @reexport using .B @reexport using .C en…

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## [Help with deSolveDiffEq](https://discourse.julialang.org/t/help-with-desolvediffeq/47497)

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**Author:** [@HerAdri](https://discourse.julialang.org/u/HerAdri)\
**Replies:** 5\
**Last updated:** [September 30, 2020, 1:33pm UTC](https://discourse.julialang.org/t/help-with-desolvediffeq/47497 "2020-09-30T13:33:25Z")

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Why with deSolveDiffEq I am not receiving all the solutions of the system, as can be seen in the examples? I only get these results 19:42:41-\>\>retcode: Default Interpolation: 1st order linear t: 2-element view(::Array{…

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## [Returning a value calculated inside the ODE function](https://discourse.julialang.org/t/returning-a-value-calculated-inside-the-ode-function/47529)

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**Author:** [@fkrauer](https://discourse.julialang.org/u/fkrauer)\
**Replies:** 1\
**Last updated:** [September 30, 2020, 12:52pm UTC](https://discourse.julialang.org/t/returning-a-value-calculated-inside-the-ode-function/47529 "2020-09-30T12:52:20Z")

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Hi I am using julia via R to simulate compartmental epidemic ODE models. Is there a way to return a value that is calculated inside the ODE function for every step of the integration? So far it only returns the states. …

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## [How to install PyPlot.jl on Windows 10 behind a firewall](https://discourse.julialang.org/t/how-to-install-pyplot-jl-on-windows-10-behind-a-firewall/30208)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 6\
**Last updated:** [September 30, 2020, 12:32pm UTC](https://discourse.julialang.org/t/how-to-install-pyplot-jl-on-windows-10-behind-a-firewall/30208 "2020-09-30T12:32:54Z")

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I am behind a firewall and have to use a proxy server. This works for normal Julia packages, but not for Python/ Conda. The following command fails: (v1.2) pkg\> build PyCall Building Conda ─→ \`C:\\Users\\NLUWFEC\\.julia\\…

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## [Is there any way to get dark mode in Pluto.jl](https://discourse.julialang.org/t/is-there-any-way-to-get-dark-mode-in-pluto-jl/47408)

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**Author:** [@Noob\_Programmer](https://discourse.julialang.org/u/Noob_Programmer)\
**Replies:** 9\
**Last updated:** [September 30, 2020, 12:29pm UTC](https://discourse.julialang.org/t/is-there-any-way-to-get-dark-mode-in-pluto-jl/47408 "2020-09-30T12:29:00Z")

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I tried Pluto notebook and i love it, i’m new to julia, coming from python is there any way i can get dark mode in pluto or is there any defaults way to choose theme.

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## [How to register my own packages?](https://discourse.julialang.org/t/how-to-register-my-own-packages/47532)

<div class="topic-metadata">

**Author:** [@iHany](https://discourse.julialang.org/u/iHany)\
**Replies:** 3\
**Last updated:** [September 30, 2020, 11:37am UTC](https://discourse.julialang.org/t/how-to-register-my-own-packages/47532 "2020-09-30T11:37:19Z")

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Hi, I’m trying to register my own package to General. As General said, I tried to register my package through JuliaHub. However, the General said " I was not able to load the package (i.e. import MyPackage failed). …

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## [In-place reverse!](https://discourse.julialang.org/t/in-place-reverse/47524)

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**Author:** [@greg\_plowman](https://discourse.julialang.org/u/greg_plowman)\
**Replies:** 4\
**Last updated:** [September 30, 2020, 11:24am UTC](https://discourse.julialang.org/t/in-place-reverse/47524 "2020-09-30T11:24:33Z")

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In-place reverse! is defined for vectors. Does it make sense to have reverse! for general arrays with other dimensions? In particular, I thought it might useful for matrices?

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## [Simple syntax for modifying specific entries of one Array based on indices from another Array?](https://discourse.julialang.org/t/simple-syntax-for-modifying-specific-entries-of-one-array-based-on-indices-from-another-array/47494)

<div class="topic-metadata">

**Author:** [@airpmb](https://discourse.julialang.org/u/airpmb)\
**Replies:** 5\
**Last updated:** [September 30, 2020, 11:07am UTC](https://discourse.julialang.org/t/simple-syntax-for-modifying-specific-entries-of-one-array-based-on-indices-from-another-array/47494 "2020-09-30T11:07:44Z")

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How would I do this? It seems like there should be some simple syntax for this but if so, I can’t find it. For example, suppose I have a 10x10 matrix A, and a 5x2 matrix idx, and the rows of idx represent row, column in…

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## [ANN: PackageGenerator.jl](https://discourse.julialang.org/t/ann-packagegenerator-jl/3300)

<div class="topic-metadata">

**Author:** [@bramtayl](https://discourse.julialang.org/u/bramtayl)\
**Replies:** 5\
**Last updated:** [September 30, 2020, 9:45am UTC](https://discourse.julialang.org/t/ann-packagegenerator-jl/3300 "2020-09-30T09:45:22Z")

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Generate packages with bells and whistles. These include: a matching github repository an activated repository on travis an appveyor project generated documentation that automatically syncs to changes on github inclu…

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## [LASSO.jl, GLMNet.jl - hyperparameters](https://discourse.julialang.org/t/lasso-jl-glmnet-jl-hyperparameters/28799)

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**Author:** [@versipellis](https://discourse.julialang.org/u/versipellis)\
**Replies:** 6\
**Last updated:** [September 30, 2020, 9:35am UTC](https://discourse.julialang.org/t/lasso-jl-glmnet-jl-hyperparameters/28799 "2020-09-30T09:35:34Z")

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I’m not seeing any documentation for such, but in LASSO.jl and GLMNet.jl, I’m looking to do the following: Specify a validation set to train hyperparameters on, rather than just using cross-validation. I know CV is bet…

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## [How to link to the repo's NEWS.md in the documentation?](https://discourse.julialang.org/t/how-to-link-to-the-repos-news-md-in-the-documentation/47477)

<div class="topic-metadata">

**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 3\
**Last updated:** [September 30, 2020, 9:23am UTC](https://discourse.julialang.org/t/how-to-link-to-the-repos-news-md-in-the-documentation/47477 "2020-09-30T09:23:19Z")

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I notice that the link to “news” in the documentation for Interpolations.jl is broken. Currently the link points to ../../NEWS.md. Given the directory structure docs/src/index.md, this appears to be the correct relative …

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## [How to floor a normed/fixed-point number in an idempotent way](https://discourse.julialang.org/t/how-to-floor-a-normed-fixed-point-number-in-an-idempotent-way/47510)

<div class="topic-metadata">

**Author:** [@Nicholas\_Montano](https://discourse.julialang.org/u/Nicholas_Montano)\
**Replies:** 10\
**Last updated:** [September 30, 2020, 8:50am UTC](https://discourse.julialang.org/t/how-to-floor-a-normed-fixed-point-number-in-an-idempotent-way/47510 "2020-09-30T08:50:05Z")

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Hello all, I am learning Julia through the MIT computational thinking course, and am curious if it’s possible to floor within a normed or fixed point type. Normally, I expect a number, once floored, to stay that same num…

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## [Adding textures to rectangles using Makie](https://discourse.julialang.org/t/adding-textures-to-rectangles-using-makie/11465)

<div class="topic-metadata">

**Author:** [@fabiangans](https://discourse.julialang.org/u/fabiangans)\
**Replies:** 4\
**Last updated:** [September 30, 2020, 8:57am UTC](https://discourse.julialang.org/t/adding-textures-to-rectangles-using-makie/11465 "2020-09-30T08:57:49Z")

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I want to create a number of textured (rotated) rectangles where the 3D corner coordinates are given in a single plot using Makie.jl or GLVizualize. I want a plot similar to this example where the earth image is plotted …

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