# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1546

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

**Page:** 1547

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## [Is the type-instability in take!(::RemoteChannel) of practical concern?](https://discourse.julialang.org/t/is-the-type-instability-in-take-remotechannel-of-practical-concern/51864)

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**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 1\
**Last updated:** [December 15, 2020, 12:15pm UTC](https://discourse.julialang.org/t/is-the-type-instability-in-take-remotechannel-of-practical-concern/51864 "2020-12-15T12:15:18Z")

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For example: julia\> using Distributed julia\> r = RemoteChannel(()-\>Channel{Bool}(Inf)) RemoteChannel{Channel{Bool}}(1, 1, 1) julia\> @code\_warntype take!(r) Variables #self#::Core.Compiler.Const(take!, false) rr::R…

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## [ReverseDiff: differentiating a function with an indexing argument](https://discourse.julialang.org/t/reversediff-differentiating-a-function-with-an-indexing-argument/51530)

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**Author:** [@jacobusmmsmit](https://discourse.julialang.org/u/jacobusmmsmit)\
**Replies:** 5\
**Last updated:** [December 15, 2020, 12:09pm UTC](https://discourse.julialang.org/t/reversediff-differentiating-a-function-with-an-indexing-argument/51530 "2020-12-15T12:09:52Z")

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I am looking to move from using ForwardDiff to ReverseDiff due to the speedup provided by compiled tapes. I would like to differentiate a function where one of the arguments is an index of the output, and then compile th…

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## [How to remove and change the default project](https://discourse.julialang.org/t/how-to-remove-and-change-the-default-project/24085)

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**Author:** [@leiteiro](https://discourse.julialang.org/u/leiteiro)\
**Replies:** 4\
**Last updated:** [December 15, 2020, 11:14am UTC](https://discourse.julialang.org/t/how-to-remove-and-change-the-default-project/24085 "2020-12-15T11:14:21Z")

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I installed JuliaPro with version 1.1.0. (on Windows). After opening Atom and starting Julia in the REPL I switch to the pkg-mode. What I see is the prompt: (ProjA) pkg\> Now the issue is that “ProjA” does not exist any…

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## [Algorithms repo on GitHub](https://discourse.julialang.org/t/algorithms-repo-on-github/51859)

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**Author:** [@berceanu](https://discourse.julialang.org/u/berceanu)\
**Replies:** 1\
**Last updated:** [December 15, 2020, 10:54am UTC](https://discourse.julialang.org/t/algorithms-repo-on-github/51859 "2020-12-15T10:54:08Z")

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Stumbled across thealgorithms.github.io and didn’t find Julia in the list of languages, is it worth contributing?

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## [How to add, subtract, and take linear combinations of ODE solutions](https://discourse.julialang.org/t/how-to-add-subtract-and-take-linear-combinations-of-ode-solutions/51791)

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**Author:** [@CosmoProf](https://discourse.julialang.org/u/CosmoProf)\
**Replies:** 2\
**Last updated:** [December 15, 2020, 10:24am UTC](https://discourse.julialang.org/t/how-to-add-subtract-and-take-linear-combinations-of-ode-solutions/51791 "2020-12-15T10:24:55Z")

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Hi, I’m solving differential equations with different sets of initial conditions, and I’m trying to figure out how to take different linear combinations of the ODE solutions (added, subtracted, multiplied by different sc…

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## [Image rotation](https://discourse.julialang.org/t/image-rotation/2637)

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**Author:** [@yalexand](https://discourse.julialang.org/u/yalexand)\
**Replies:** 10\
**Last updated:** [December 15, 2020, 10:17am UTC](https://discourse.julialang.org/t/image-rotation/2637 "2020-12-15T10:17:14Z")

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Hi All, I can’t find an analog for Matlab “imrotate” function. Maybe I overlooked it, or really there isn’t such thing? Here it is in Matlab, to save you clicking: imrotate Rotate image. B = imrotate(A,ANGLE) rot…

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## [Retrieving the Hessian, and eventually calculating the standard errors using JuMP](https://discourse.julialang.org/t/retrieving-the-hessian-and-eventually-calculating-the-standard-errors-using-jump/51823)

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**Author:** [@jovansam](https://discourse.julialang.org/u/jovansam)\
**Replies:** 3\
**Last updated:** [December 15, 2020, 9:47am UTC](https://discourse.julialang.org/t/retrieving-the-hessian-and-eventually-calculating-the-standard-errors-using-jump/51823 "2020-12-15T09:47:47Z")

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After obtaining the optimum, I am interested in finding the Hessian. I then intend to use this to find standard errors. More like what is done here, but that code refers to old JuMP and I am having trouble translating it…

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## [Julia not accepting this constraint. No method matching cartesian index](https://discourse.julialang.org/t/julia-not-accepting-this-constraint-no-method-matching-cartesian-index/51850)

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**Author:** [@prit](https://discourse.julialang.org/u/prit)\
**Replies:** 1\
**Last updated:** [December 15, 2020, 9:13am UTC](https://discourse.julialang.org/t/julia-not-accepting-this-constraint-no-method-matching-cartesian-index/51850 "2020-12-15T09:13:33Z")

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I have the following code in which the JuMP constraint is throwing an error. using JuMP using MosekTools K = 3 N = 2 penalties = \[1.0, 3.9, 8.7\] function A\_tau(r::Number, n::Number, tau::Float64) fac = 1 for m …

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## [Hidden code](https://discourse.julialang.org/t/hidden-code/16232)

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**Author:** [@rohqhq](https://discourse.julialang.org/u/rohqhq)\
**Replies:** 26\
**Last updated:** [December 15, 2020, 8:07am UTC](https://discourse.julialang.org/t/hidden-code/16232 "2020-12-15T08:07:07Z")

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I’m new to Julia and almost new to programming, so sorry if the question is stupid. Is Julia a programming language where the code is hidden from a user (like C) or not (like Python)? I found information that I can use U…

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## [\[ANN\] UnitTestDesign: All-pairs, and other algorithms to generate unit testing parameters](https://discourse.julialang.org/t/ann-unittestdesign-all-pairs-and-other-algorithms-to-generate-unit-testing-parameters/51849)

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**Author:** [@adolgert](https://discourse.julialang.org/u/adolgert)\
**Replies:** 3\
**Last updated:** [December 15, 2020, 5:48am UTC](https://discourse.julialang.org/t/ann-unittestdesign-all-pairs-and-other-algorithms-to-generate-unit-testing-parameters/51849 "2020-12-15T05:48:05Z")

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If you have a function that has a lot of parameters, that takes some time to run, and that you want to test well, then you want to test it against a small set of test cases that will still find all of its faults. A thoro…

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## [Calling a Julia function from Python--pass a dictionary of arguments and get an array returned](https://discourse.julialang.org/t/calling-a-julia-function-from-python-pass-a-dictionary-of-arguments-and-get-an-array-returned/32052)

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**Author:** [@00krishna](https://discourse.julialang.org/u/00krishna)\
**Replies:** 4\
**Last updated:** [December 15, 2020, 2:41am UTC](https://discourse.julialang.org/t/calling-a-julia-function-from-python-pass-a-dictionary-of-arguments-and-get-an-array-returned/32052 "2020-12-15T02:41:53Z")

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I am writing a little package in julia, but I also need to plug the package into an existing python jupyter notebook, etc. So I was hoping someone could tell me how to call a Julia function from Python 3. That is, I wan…

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## [Tullio: overwrite existing matrix instead of creating a new matrix?](https://discourse.julialang.org/t/tullio-overwrite-existing-matrix-instead-of-creating-a-new-matrix/51834)

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**Author:** [@dilumaluthge](https://discourse.julialang.org/u/dilumaluthge)\
**Replies:** 4\
**Last updated:** [December 15, 2020, 12:15am UTC](https://discourse.julialang.org/t/tullio-overwrite-existing-matrix-instead-of-creating-a-new-matrix/51834 "2020-12-15T00:15:24Z")

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I can use Tullio to define a matrix multiplication function matmul(A, B) as such: using Tullio matmul(A, B) = @tullio C\[i, k\] := A\[i, j\] \* B\[j, k\] I’d like to also define a function matmul!(C, A, B) that stores the re…

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## [Again, another simple 2D plotting tool](https://discourse.julialang.org/t/again-another-simple-2d-plotting-tool/51837)

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**Author:** [@ig-or](https://discourse.julialang.org/u/ig-or)\
**Replies:** 0\
**Last updated:** [December 15, 2020, 12:09am UTC](https://discourse.julialang.org/t/again-another-simple-2d-plotting-tool/51837 "2020-12-15T00:09:49Z")

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Hello, made another 2D plotting tool for Julia… QWTWPlot.jl maybe it could be useful for quick data analysis. It does not have many features but allows to quickly create a number of “connected” plots, like when you mov…

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## [Help with @generated](https://discourse.julialang.org/t/help-with-generated/51829)

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**Author:** [@gmouts](https://discourse.julialang.org/u/gmouts)\
**Replies:** 1\
**Last updated:** [December 14, 2020, 11:32pm UTC](https://discourse.julialang.org/t/help-with-generated/51829 "2020-12-14T23:32:16Z")

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Apart from what I am asking below, I would really appreciate if someone could point me to some resource that explains the usage of the macro generated. I want to write a function that will loop through an array and will…

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## [DoubleFloats.jl -\> Double128 | Quad64?](https://discourse.julialang.org/t/doublefloats-jl-double128-quad64/51049)

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**Author:** [@lrnv](https://discourse.julialang.org/u/lrnv)\
**Replies:** 54\
**Last updated:** [December 14, 2020, 11:10pm UTC](https://discourse.julialang.org/t/doublefloats-jl-double128-quad64/51049 "2020-12-14T23:10:39Z")

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Hey, I need some kind of high precision arithmetics to do computations, and I’m trying to find the best balance between runtime and precision. Using BigFloat, i found out that 256bits BigFloats give me good enough resul…

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## [Unknown error when using ccall to work with Apache Arrow's GLib interface](https://discourse.julialang.org/t/unknown-error-when-using-ccall-to-work-with-apache-arrows-glib-interface/51794)

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**Author:** [@s-kap](https://discourse.julialang.org/u/s-kap)\
**Replies:** 3\
**Last updated:** [December 14, 2020, 10:21pm UTC](https://discourse.julialang.org/t/unknown-error-when-using-ccall-to-work-with-apache-arrows-glib-interface/51794 "2020-12-14T22:21:39Z")

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Hey all, Context: Apache Arrow is an in memory columnar format has some very speedy IO implementations in c++ has a C interface using GLib Since it’s an in-memory format, I’d like to perform IO in cpp, and then conv…

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## [Easier way to split-apply-combine in DataFrames.jl](https://discourse.julialang.org/t/easier-way-to-split-apply-combine-in-dataframes-jl/51779)

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**Author:** [@stefanjwojcik](https://discourse.julialang.org/u/stefanjwojcik)\
**Replies:** 5\
**Last updated:** [December 14, 2020, 10:03pm UTC](https://discourse.julialang.org/t/easier-way-to-split-apply-combine-in-dataframes-jl/51779 "2020-12-14T22:03:01Z")

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I am updating some code that uses DataFrames.jl. I formerly used the by command and the aggregate command to execute commands over multiple columns, but it looks like these commands were deprecated recently. The updates …

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## [List of JuMP solvers that have a compute\_conflict! function implemented](https://discourse.julialang.org/t/list-of-jump-solvers-that-have-a-compute-conflict-function-implemented/51825)

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**Author:** [@bhalonen](https://discourse.julialang.org/u/bhalonen)\
**Replies:** 2\
**Last updated:** [December 14, 2020, 9:05pm UTC](https://discourse.julialang.org/t/list-of-jump-solvers-that-have-a-compute-conflict-function-implemented/51825 "2020-12-14T21:05:19Z")

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I am interested in using the compute\_conflict! function in JuMP, I noticed that Gurobi.jl and CPLEX.jl are cited in the documentation in a comment as available solvers. I also found that Xpress.jl has the same functional…

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## [Gurobi constraint](https://discourse.julialang.org/t/gurobi-constraint/51798)

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**Author:** [@jay-dave](https://discourse.julialang.org/u/jay-dave)\
**Replies:** 2\
**Last updated:** [December 14, 2020, 8:59pm UTC](https://discourse.julialang.org/t/gurobi-constraint/51798 "2020-12-14T20:59:55Z")

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Below is the minimum example of the model I am able to solve. Why is the constraint @constraint(model, Cost == (x-y)\*z) allowed in Gurobi? Isn’t it nonlinear? using JuMP using Gurobi model = Model(with\_optimizer(Gurobi.…

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## [Help avoid a bit of python](https://discourse.julialang.org/t/help-avoid-a-bit-of-python/51802)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 4\
**Last updated:** [December 14, 2020, 8:54pm UTC](https://discourse.julialang.org/t/help-avoid-a-bit-of-python/51802 "2020-12-14T20:54:51Z")

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I’m using the Picamera library to grab an image from a Pi Camera on a Raspberry Pi. The main Python code in question is (found here): import io import time import picamera from PIL import Image # Create the in-memory s…

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## [NLopt not optimising](https://discourse.julialang.org/t/nlopt-not-optimising/51796)

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**Author:** [@Massimiliano\_Vasile](https://discourse.julialang.org/u/Massimiliano_Vasile)\
**Replies:** 13\
**Last updated:** [December 14, 2020, 8:53pm UTC](https://discourse.julialang.org/t/nlopt-not-optimising/51796 "2020-12-14T20:53:19Z")

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Hi I am rather new to Julia and I am experimenting with NLopt. I ran the tests on github and they work fine but then I tried my own objective and constraints. function ps(x,grad) return x\[1\] end function ps\_con(x,gr…

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## [Compilation times for huge programs](https://discourse.julialang.org/t/compilation-times-for-huge-programs/51821)

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**Author:** [@lmiq](https://discourse.julialang.org/u/lmiq)\
**Replies:** 6\
**Last updated:** [December 14, 2020, 8:41pm UTC](https://discourse.julialang.org/t/compilation-times-for-huge-programs/51821 "2020-12-14T20:41:41Z")

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I have more a general curiosity about compilation times. Some software in low-level languages (C, Fortran, C++) that we download from time to time take several minutes to compile. Nevertheless, their execution needs to b…

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## [In-place allocations in DifferentialEquations](https://discourse.julialang.org/t/in-place-allocations-in-differentialequations/51813)

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**Author:** [@oeyd](https://discourse.julialang.org/u/oeyd)\
**Replies:** 9\
**Last updated:** [December 14, 2020, 7:59pm UTC](https://discourse.julialang.org/t/in-place-allocations-in-differentialequations/51813 "2020-12-14T19:59:15Z")

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I am wondering why the code below allocates as much memory as it does despite using an in-place function definition. Is this normal or is there a way to avoid these allocations? using DifferentialEquations function ode…

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## [Difference result between insertcols! and transform! in spreading one column to many columns](https://discourse.julialang.org/t/difference-result-between-insertcols-and-transform-in-spreading-one-column-to-many-columns/51777)

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**Author:** [@rocco\_sprmnt21](https://discourse.julialang.org/u/rocco_sprmnt21)\
**Replies:** 4\
**Last updated:** [December 14, 2020, 7:48pm UTC](https://discourse.julialang.org/t/difference-result-between-insertcols-and-transform-in-spreading-one-column-to-many-columns/51777 "2020-12-14T19:48:05Z")

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I tried to understand how this script here works and I tried to reproduce it in other ways: this with insertcols! it seems to work df=DataFrame(name=\["James Smith 39","Michel Smith 41","Maria Garcia 19"\], …

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## [How to read long output from external command?](https://discourse.julialang.org/t/how-to-read-long-output-from-external-command/47870)

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**Author:** [@aplavin](https://discourse.julialang.org/u/aplavin)\
**Replies:** 4\
**Last updated:** [December 14, 2020, 7:44pm UTC](https://discourse.julialang.org/t/how-to-read-long-output-from-external-command/47870 "2020-12-14T19:44:38Z")

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I’m trying to read all the output from an external program like this (MWE): out = Pipe() run(pipeline(\`head -c10 /dev/urandom\`, stdout=out), wait=true) close(out.in) read(out) |\> length # shows "10" as expected This is…

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## [Incompatibility Queryverse / DataFrames?](https://discourse.julialang.org/t/incompatibility-queryverse-dataframes/51822)

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**Author:** [@tlorans](https://discourse.julialang.org/u/tlorans)\
**Replies:** 2\
**Last updated:** [December 14, 2020, 7:28pm UTC](https://discourse.julialang.org/t/incompatibility-queryverse-dataframes/51822 "2020-12-14T19:28:58Z")

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Hello, I try to use simultaneously Queryverse and DataFrames packages, but it seems there is some incompatibility: julia\> Pkg.add("Queryverse") Updating registry at \`~/.julia/registries/General\` ####################…

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## [Choosing a simpler print than println ? :)](https://discourse.julialang.org/t/choosing-a-simpler-print-than-println/51820)

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**Author:** [@vedasulo](https://discourse.julialang.org/u/vedasulo)\
**Replies:** 6\
**Last updated:** [December 14, 2020, 6:45pm UTC](https://discourse.julialang.org/t/choosing-a-simpler-print-than-println/51820 "2020-12-14T18:45:43Z")

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I’ve read materials liked some and some are liking. :slight\_smile: . Found easy things , even easy to write a function and a unicode. But All the way through those cool use why julia choose println (print is more natur…

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## [Any French working days/holiday calendar?](https://discourse.julialang.org/t/any-french-working-days-holiday-calendar/51808)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 2\
**Last updated:** [December 14, 2020, 6:04pm UTC](https://discourse.julialang.org/t/any-french-working-days-holiday-calendar/51808 "2020-12-14T18:04:43Z")

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Is there any package that returns false/true (or even better a \[0,1\] float for sub-country holidays averaged by population… yeahh… but this would be too much :slight\_smile: :slight\_smile: ) for something like isholiday.(…

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## [Package for time series?](https://discourse.julialang.org/t/package-for-time-series/29555)

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**Author:** [@Donkeyfish87](https://discourse.julialang.org/u/Donkeyfish87)\
**Replies:** 10\
**Last updated:** [December 14, 2020, 5:59pm UTC](https://discourse.julialang.org/t/package-for-time-series/29555 "2020-12-14T17:59:42Z")

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Are there any Julia packages for time series analysis? Like arma, arima, vector autoregressions etc. I’ve tried looking around a bit, but didn’t find anything. Thanks.

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## [Why there is no GNU+linux os mentioned in github of julia instead all windows?](https://discourse.julialang.org/t/why-there-is-no-gnu-linux-os-mentioned-in-github-of-julia-instead-all-windows/51814)

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**Author:** [@vedasulo](https://discourse.julialang.org/u/vedasulo)\
**Replies:** 1\
**Last updated:** [December 14, 2020, 5:47pm UTC](https://discourse.julialang.org/t/why-there-is-no-gnu-linux-os-mentioned-in-github-of-julia-instead-all-windows/51814 "2020-12-14T17:47:28Z")

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As Opensource community, I feel sad when i don’t see mentioning gnu/linux os in github readme of julia. Instead using some Proprietary os in priority.

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