# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1877

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

**Page:** 1878

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## [Promote failed to change any arguments](https://discourse.julialang.org/t/promote-failed-to-change-any-arguments/31361)

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**Author:** [@venuur](https://discourse.julialang.org/u/venuur)\
**Replies:** 5\
**Last updated:** [November 22, 2019, 2:54pm UTC](https://discourse.julialang.org/t/promote-failed-to-change-any-arguments/31361 "2019-11-22T14:54:19Z")

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I am having trouble figuring out how to implement promotions for a type. The main idea is the create a class that tracks operations applied to a variable type. This is perhaps not so different from Flux, but I wanted to …

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## [Accessing the solution of differential equations: understanding alloc](https://discourse.julialang.org/t/accessing-the-solution-of-differential-equations-understanding-alloc/31364)

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**Author:** [@Egwene\_al\_Vere](https://discourse.julialang.org/u/Egwene_al_Vere)\
**Replies:** 3\
**Last updated:** [November 22, 2019, 2:30pm UTC](https://discourse.julialang.org/t/accessing-the-solution-of-differential-equations-understanding-alloc/31364 "2019-11-22T14:30:41Z")

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I’m preallocating an array for the solution of an ODE at each time step, for post-processing. However, julia --track-allocation=user foo.jl still reports large allocations. To simplify with @btime: using DifferentialEqu…

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## [Accessing 2D array/matrix values with Booleans](https://discourse.julialang.org/t/accessing-2d-array-matrix-values-with-booleans/31384)

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**Author:** [@keeler](https://discourse.julialang.org/u/keeler)\
**Replies:** 3\
**Last updated:** [November 22, 2019, 2:03pm UTC](https://discourse.julialang.org/t/accessing-2d-array-matrix-values-with-booleans/31384 "2019-11-22T14:03:26Z")

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Take a matrix A and a vector of Booleans , say, booleRand (whose length is the same as the number of columns or rows in A). I want to be able to access entire rows or columns using the Boolean vector. I am a bit surpris…

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## [For loop in function and multiplication of larger matrices, slow speed in parallel](https://discourse.julialang.org/t/for-loop-in-function-and-multiplication-of-larger-matrices-slow-speed-in-parallel/31258)

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**Author:** [@luboshanus](https://discourse.julialang.org/u/luboshanus)\
**Replies:** 3\
**Last updated:** [November 22, 2019, 1:42pm UTC](https://discourse.julialang.org/t/for-loop-in-function-and-multiplication-of-larger-matrices-slow-speed-in-parallel/31258 "2019-11-22T13:42:58Z")

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Hello, I’d like to understand how does the performance of large for loops in julia work? Running the same function on one core or on multiple cores does not give me similar time results. The computer has 48 physical co…

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## [StatsPlots dendrogram on the right side or rotated](https://discourse.julialang.org/t/statsplots-dendrogram-on-the-right-side-or-rotated/31348)

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**Author:** [@oheil](https://discourse.julialang.org/u/oheil)\
**Replies:** 3\
**Last updated:** [November 22, 2019, 12:39pm UTC](https://discourse.julialang.org/t/statsplots-dendrogram-on-the-right-side-or-rotated/31348 "2019-11-22T12:39:42Z")

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I try to generate a heatmap with clustered rows and columns and want the dendrograms displayed on top and on the side. The top dendrogram is no problem, but I can’t find a way to create a dendrogram which is displayed fr…

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## [Feedback on Julia 1.3 RC5](https://discourse.julialang.org/t/feedback-on-julia-1-3-rc5/31362)

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**Author:** [@StevenSiew](https://discourse.julialang.org/u/StevenSiew)\
**Replies:** 8\
**Last updated:** [November 22, 2019, 12:36pm UTC](https://discourse.julialang.org/t/feedback-on-julia-1-3-rc5/31362 "2019-11-22T12:36:54Z")

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I have started using Julia 1.3 RC5 and I would like to provide some feedback Firstly, Multithreading makes things easy to paralyse because unlike Distributed, I don’t have to use the keyword @everywhere everywhere and …

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## [Improving Performance of this Code](https://discourse.julialang.org/t/improving-performance-of-this-code/31326)

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**Author:** [@jmcastro2109](https://discourse.julialang.org/u/jmcastro2109)\
**Replies:** 12\
**Last updated:** [November 22, 2019, 11:59am UTC](https://discourse.julialang.org/t/improving-performance-of-this-code/31326 "2019-11-22T11:59:25Z")

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Hello! I am trying to solve a big model and at the core I have the following loop which essentially solves a Backward Induction Problem. In what follows I provide a MWE. In my model, I am solving this problem many many…

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## [Save Array of Arrays in HDF5](https://discourse.julialang.org/t/save-array-of-arrays-in-hdf5/31359)

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**Author:** [@jacob-roth](https://discourse.julialang.org/u/jacob-roth)\
**Replies:** 1\
**Last updated:** [November 22, 2019, 9:26am UTC](https://discourse.julialang.org/t/save-array-of-arrays-in-hdf5/31359 "2019-11-22T09:26:43Z")

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Continuing the discussion from here and here, how can I best save a large number of arrays using HDF5? And more generally, how can I save an array of arrays? I know that HDF5 doesn’t support array of arrays, so trying t…

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## [Plots.jl/Makie.jl tick locations?](https://discourse.julialang.org/t/plots-jl-makie-jl-tick-locations/31371)

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**Author:** [@Raf](https://discourse.julialang.org/u/Raf)\
**Replies:** 1\
**Last updated:** [November 22, 2019, 7:17am UTC](https://discourse.julialang.org/t/plots-jl-makie-jl-tick-locations/31371 "2019-11-22T07:17:14Z")

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I’m wondering if there is a way of specifying the location of the ticks/ labels within each x/y value - ie start, center, end. For an example application, sometimes you want the month to show as the whole period, not th…

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## [\[ANN\] PrettyTables 0.7.0](https://discourse.julialang.org/t/ann-prettytables-0-7-0/31369)

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**Author:** [@Ronis\_BR](https://discourse.julialang.org/u/Ronis_BR)\
**Replies:** 0\
**Last updated:** [November 22, 2019, 12:36am UTC](https://discourse.julialang.org/t/ann-prettytables-0-7-0/31369 "2019-11-22T00:36:31Z")

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Hi! I just tag a new version of PrettyTables.jl (v0.7.0). This version has two major improvements. HTML backend Now, PrettyTables.jl can print tables in HTML format. This is the very first version to support this back…

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## [Isapprox documentation has argument norm, but call signature does not?](https://discourse.julialang.org/t/isapprox-documentation-has-argument-norm-but-call-signature-does-not/31072)

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**Author:** [@jtg](https://discourse.julialang.org/u/jtg)\
**Replies:** 5\
**Last updated:** [November 21, 2019, 11:01pm UTC](https://discourse.julialang.org/t/isapprox-documentation-has-argument-norm-but-call-signature-does-not/31072 "2019-11-21T23:01:17Z")

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I noticed this trying to extend the function. I am using: Julia Version 1.3.0-rc4.1 Commit 8c4656b97a (2019-10-15 14:08 UTC) Platform Info: OS: macOS (x86\_64-apple-darwin18.6.0) CPU: Intel(R) Core(TM) i5-8279U CPU…

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## [How can I make this plot?](https://discourse.julialang.org/t/how-can-i-make-this-plot/31278)

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**Author:** [@mthelm85](https://discourse.julialang.org/u/mthelm85)\
**Replies:** 11\
**Last updated:** [November 21, 2019, 4:37pm UTC](https://discourse.julialang.org/t/how-can-i-make-this-plot/31278 "2019-11-21T16:37:01Z")

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I came across this article on Freakonometrics and it has the following really nice plot in it (generated with R, I believe): Has anyone seen anything similar plotted in Julia or does anyone know if this is at least po…

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## [Trying to understand the "gradient()" function from the Flux.jl/Zygote.jl package](https://discourse.julialang.org/t/trying-to-understand-the-gradient-function-from-the-flux-jl-zygote-jl-package/31328)

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**Author:** [@rapasite](https://discourse.julialang.org/u/rapasite)\
**Replies:** 4\
**Last updated:** [November 21, 2019, 9:19pm UTC](https://discourse.julialang.org/t/trying-to-understand-the-gradient-function-from-the-flux-jl-zygote-jl-package/31328 "2019-11-21T21:19:45Z")

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Hi there, need some help to dig into https://github.com/FluxML/Zygote.jl/blob/master/src/compiler/interface.jl. So it start like this: function gradient(f, args...) y, back = pullback(f, args...) return back(sensi…

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## [ANN: QuickPOMDPs and POMDPs v0.8](https://discourse.julialang.org/t/ann-quickpomdps-and-pomdps-v0-8/31357)

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**Author:** [@zsunberg](https://discourse.julialang.org/u/zsunberg)\
**Replies:** 0\
**Last updated:** [November 21, 2019, 9:05pm UTC](https://discourse.julialang.org/t/ann-quickpomdps-and-pomdps-v0-8/31357 "2019-11-21T21:05:34Z")

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Hi All, I’d like to announce some enhancements to the POMDPs ecosystem. First, we have introduced the QuickPOMDPs.jl package, which makes it much easier to define Markov decision processes (MDPs) and partially observabl…

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## [Optimization of Code for NaN Operations](https://discourse.julialang.org/t/optimization-of-code-for-nan-operations/31339)

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**Author:** [@natgeo-wong](https://discourse.julialang.org/u/natgeo-wong)\
**Replies:** 3\
**Last updated:** [November 21, 2019, 8:50pm UTC](https://discourse.julialang.org/t/optimization-of-code-for-nan-operations/31339 "2019-11-21T20:50:33Z")

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Hi, I’ve been trying to perform operations on Arrays that may have missing values, using the below prototype function: function nanop(f::Function,data::Array;dim=1) ndim = ndims(data); dsize = size(data); if nd…

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## [Porting an example from QuantEcon.jl to POMDPs.jl](https://discourse.julialang.org/t/porting-an-example-from-quantecon-jl-to-pomdps-jl/16377)

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**Author:** [@amrods](https://discourse.julialang.org/u/amrods)\
**Replies:** 1\
**Last updated:** [November 21, 2019, 8:23pm UTC](https://discourse.julialang.org/t/porting-an-example-from-quantecon-jl-to-pomdps-jl/16377 "2019-11-21T20:23:22Z")

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Just for fun (and to learn about POMDP) I am porting an example of dynamic programming from QuantEcon.jl to POMDPs.jl. The example is available here: https://lectures.quantecon.org/jl/discrete\_dp.html#example-a-growth-mo…

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## [How to proper debug Julia?](https://discourse.julialang.org/t/how-to-proper-debug-julia/31234)

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**Author:** [@adrpo](https://discourse.julialang.org/u/adrpo)\
**Replies:** 6\
**Last updated:** [November 21, 2019, 7:31pm UTC](https://discourse.julialang.org/t/how-to-proper-debug-julia/31234 "2019-11-21T19:31:27Z")

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Hi all, I have some code that works fine in Atom/Juno debugger but when I run it directly in Julia it goes in some sort of cycle and spins forever. Any ideas on how to debug such a thing? I have tried to attach to the j…

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## [StatsPlots, precompiling error](https://discourse.julialang.org/t/statsplots-precompiling-error/31354)

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**Author:** [@Gunter\_Faes](https://discourse.julialang.org/u/Gunter_Faes)\
**Replies:** 0\
**Last updated:** [November 21, 2019, 7:20pm UTC](https://discourse.julialang.org/t/statsplots-precompiling-error/31354 "2019-11-21T19:20:43Z")

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Hi, I am currently experimenting with my nVIDIA Jetson Nano and have had no problems so far. Now I want to use StatsPlots in addition to PLots, but for StastPlots it is noted in the precompiling phase that the Arpack pa…

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## [Calculating the \`k\` smallest positive eigenvalues of a matrix with ARPACK](https://discourse.julialang.org/t/calculating-the-k-smallest-positive-eigenvalues-of-a-matrix-with-arpack/28864)

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**Author:** [@sergevic](https://discourse.julialang.org/u/sergevic)\
**Replies:** 25\
**Last updated:** [November 21, 2019, 7:13pm UTC](https://discourse.julialang.org/t/calculating-the-k-smallest-positive-eigenvalues-of-a-matrix-with-arpack/28864 "2019-11-21T19:13:20Z")

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I have a sqaure matrix that is not necessarily positive definite, for example rand(10000,10000), and I’m trying to obtain the k smallest positive eigenvalues with the command eigs() from ARPACK. How can I achieve that pr…

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## [Gradient of a Hessian dependent loss function](https://discourse.julialang.org/t/gradient-of-a-hessian-dependent-loss-function/31322)

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**Author:** [@mtgd](https://discourse.julialang.org/u/mtgd)\
**Replies:** 1\
**Last updated:** [November 21, 2019, 6:35pm UTC](https://discourse.julialang.org/t/gradient-of-a-hessian-dependent-loss-function/31322 "2019-11-21T18:35:38Z")

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For my application it would be useful to have a loss function that depends on the Hessian of a model. Computing the Hessian with respect to the input variable (using Tracker) works fine, but trying to get the gradient w…

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## [Save PyPlot figure as SVG file with text rendered as text, not path](https://discourse.julialang.org/t/save-pyplot-figure-as-svg-file-with-text-rendered-as-text-not-path/31288)

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**Author:** [@hrchen](https://discourse.julialang.org/u/hrchen)\
**Replies:** 2\
**Last updated:** [November 21, 2019, 4:34pm UTC](https://discourse.julialang.org/t/save-pyplot-figure-as-svg-file-with-text-rendered-as-text-not-path/31288 "2019-11-21T16:34:07Z")

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I want to save a PyPlot figure as an SVG file with the text in the figure rendered as editable text, not as a path. I read that in Python one can do: plt.rcParams\['svg.fonttype'\] = 'none' but the following doesn’t work w…

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## [Current practice for specifying custom target dependencies?](https://discourse.julialang.org/t/current-practice-for-specifying-custom-target-dependencies/31349)

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**Author:** [@garborg](https://discourse.julialang.org/u/garborg)\
**Replies:** 2\
**Last updated:** [November 21, 2019, 4:10pm UTC](https://discourse.julialang.org/t/current-practice-for-specifying-custom-target-dependencies/31349 "2019-11-21T16:10:15Z")

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I’m looking to specify extra dependencies for code in an ‘example’ dir and separately for code in a ‘benchmark’ dir of a package. Akin to how ‘targets’ and ‘extras’ works for test dependencies. Early discussions I saw …

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## [Check whether the type of an object is from a package not loaded](https://discourse.julialang.org/t/check-whether-the-type-of-an-object-is-from-a-package-not-loaded/31344)

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**Author:** [@tlienart](https://discourse.julialang.org/u/tlienart)\
**Replies:** 2\
**Last updated:** [November 21, 2019, 2:03pm UTC](https://discourse.julialang.org/t/check-whether-the-type-of-an-object-is-from-a-package-not-loaded/31344 "2019-11-21T14:03:44Z")

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I have a package A in which I’d like to have a functionality foo which works on AbstractArray but does something different on LazyArrays.ApplyArray. twist: I would like not to have LazyArrays loaded in A. Is this pos…

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## [Periodic Schur decomposition](https://discourse.julialang.org/t/periodic-schur-decomposition/30682)

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**Author:** [@rveltz](https://discourse.julialang.org/u/rveltz)\
**Replies:** 3\
**Last updated:** [November 21, 2019, 2:31pm UTC](https://discourse.julialang.org/t/periodic-schur-decomposition/30682 "2019-11-21T14:31:03Z")

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Hi, I am wondering if anybody has implemented, and is willing to share, a periodic Schur decomposition. The first paper mentioning it is D. Kressner, An efficient and reliable implementation of the periodic qz algorith…

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## [CSV, DataFrames problems with threads](https://discourse.julialang.org/t/csv-dataframes-problems-with-threads/31318)

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**Author:** [@Rudi79](https://discourse.julialang.org/u/Rudi79)\
**Replies:** 2\
**Last updated:** [November 21, 2019, 2:30pm UTC](https://discourse.julialang.org/t/csv-dataframes-problems-with-threads/31318 "2019-11-21T14:30:44Z")

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Today I encountered an odd problem: using CSV, DataFrames dt = DataFrame(a = rand(10000), b = rand(10000), c = rand(10000)) CSV.write("test.csv", dt) df = CSV.File("test.csv") |\> DataFrame! df\[(ismissing.(df.a)) .| (is…

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## [Anyone using a PAID source for Sp500 options data specifically 30 day mean implied volatility?](https://discourse.julialang.org/t/anyone-using-a-paid-source-for-sp500-options-data-specifically-30-day-mean-implied-volatility/31324)

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**Author:** [@anon97116444](https://discourse.julialang.org/u/anon97116444)\
**Replies:** 8\
**Last updated:** [November 21, 2019, 2:24pm UTC](https://discourse.julialang.org/t/anyone-using-a-paid-source-for-sp500-options-data-specifically-30-day-mean-implied-volatility/31324 "2019-11-21T14:24:24Z")

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I can’t seem to find any discussion on discourse about live options data? I’m looking for the following. date,time,symbol,last,volume, open interest, 30 day mean implied volatility. don’t need HFT just 1 - 5 minutes w…

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## [What is Julia's equivalent of R's %in%](https://discourse.julialang.org/t/what-is-julias-equivalent-of-rs-in/28720)

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**Author:** [@Luigi\_Marongiu](https://discourse.julialang.org/u/Luigi_Marongiu)\
**Replies:** 9\
**Last updated:** [November 21, 2019, 2:16pm UTC](https://discourse.julialang.org/t/what-is-julias-equivalent-of-rs-in/28720 "2019-11-21T14:16:10Z")

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hello, I have two different dataframes with different columns and headers, but the columns Start and Start\_site are related and in particular I want to select the rows of the first dataframe with Start matching the seco…

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## [Inner constructors with parametric types, can't seem to get them to work for me](https://discourse.julialang.org/t/inner-constructors-with-parametric-types-cant-seem-to-get-them-to-work-for-me/31337)

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**Author:** [@tlnagy](https://discourse.julialang.org/u/tlnagy)\
**Replies:** 3\
**Last updated:** [November 21, 2019, 1:56pm UTC](https://discourse.julialang.org/t/inner-constructors-with-parametric-types-cant-seem-to-get-them-to-work-for-me/31337 "2019-11-21T13:56:13Z")

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Say I have a type that looks the following: julia\> struct Test{T, N, A} \<: AbstractArray{T, N} a::Dict{NTuple{N, Int}, String} b::Type{T} c::A d::Array{T, 2} funct…

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## [Trignometric functions on GPU](https://discourse.julialang.org/t/trignometric-functions-on-gpu/31338)

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**Author:** [@ennvvy](https://discourse.julialang.org/u/ennvvy)\
**Replies:** 4\
**Last updated:** [November 21, 2019, 8:55am UTC](https://discourse.julialang.org/t/trignometric-functions-on-gpu/31338 "2019-11-21T08:55:17Z")

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I tried executing a simple function involving sin and cos as below: using CUDAdrv,CUDAnative,CuArrays sine(x::Float32) = sin(x) cosine(x::Float32) = cos(x) CuArrays.@cufunc sine(x::Real) = sin(x) CuArrays.@cufunc cosin…

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## [Performance of the iterator approach](https://discourse.julialang.org/t/performance-of-the-iterator-approach/31293)

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**Author:** [@alanderos](https://discourse.julialang.org/u/alanderos)\
**Replies:** 3\
**Last updated:** [November 21, 2019, 7:27am UTC](https://discourse.julialang.org/t/performance-of-the-iterator-approach/31293 "2019-11-21T07:27:11Z")

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I started using IterativeSolvers.jl in some of my work and found the iterator-based code to be easy on the eyes and rather slick. It seems to me that any Julia implementation of an iterative algorithm ought to adopt this…

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