# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1357

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

**Page:** 1358

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## [Issue solving 2D wave equation with ModelingToolkit.jl](https://discourse.julialang.org/t/issue-solving-2d-wave-equation-with-modelingtoolkit-jl/62963)

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**Author:** [@apattyn](https://discourse.julialang.org/u/apattyn)\
**Replies:** 19\
**Last updated:** [June 17, 2021, 4:30pm UTC](https://discourse.julialang.org/t/issue-solving-2d-wave-equation-with-modelingtoolkit-jl/62963 "2021-06-17T16:30:25Z")

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Issue I was looking at using ModelingToolkit.jl and was playing around by trying to solve the 2D wave equation. \\frac{d^{2}u}{dt^{2}} = c^{2}\\frac{d^{2}u}{dx^{2}} However, the solution it outputs isn’t what I would ex…

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## [Stop(msg) Julia Program](https://discourse.julialang.org/t/stop-msg-julia-program/10051)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 4\
**Last updated:** [June 17, 2021, 4:03pm UTC](https://discourse.julialang.org/t/stop-msg-julia-program/10051 "2021-06-17T16:03:19Z")

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could you add a stop(msg) function that works like error(msg), but replaces the word ERROR with STOP and does not print a stack backtrace? /iaw

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## [How to avoid printing "Edit or run this notebook" button?](https://discourse.julialang.org/t/how-to-avoid-printing-edit-or-run-this-notebook-button/63019)

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**Author:** [@runjaj](https://discourse.julialang.org/u/runjaj)\
**Replies:** 0\
**Last updated:** [June 16, 2021, 2:16pm UTC](https://discourse.julialang.org/t/how-to-avoid-printing-edit-or-run-this-notebook-button/63019 "2021-06-16T14:16:40Z")

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I export a Pluto notebook as a static html file and everything is fine. Then, I want to print the file but it gets the “Edit or run notebook” button. Is there any way to remove it? Solved (June 17, 2021): I have just fo…

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## [Can Symbolics.jl build\_function() be used with median() and other functions that require sort?](https://discourse.julialang.org/t/can-symbolics-jl-build-function-be-used-with-median-and-other-functions-that-require-sort/62908)

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**Author:** [@DenisTitov](https://discourse.julialang.org/u/DenisTitov)\
**Replies:** 5\
**Last updated:** [June 17, 2021, 2:41pm UTC](https://discourse.julialang.org/t/can-symbolics-jl-build-function-be-used-with-median-and-other-functions-that-require-sort/62908 "2021-06-17T14:41:29Z")

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I started using Symbolics.jl build\_function() to accelerate various calculations and it works beautifully in many situations. I currently use it mostly to accelerate loss function calculation for curve fitting but I susp…

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## [Using WGLMakie.jl with Dash.jl](https://discourse.julialang.org/t/using-wglmakie-jl-with-dash-jl/63075)

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**Author:** [@miki\_berkovich](https://discourse.julialang.org/u/miki_berkovich)\
**Replies:** 7\
**Last updated:** [June 17, 2021, 2:34pm UTC](https://discourse.julialang.org/t/using-wglmakie-jl-with-dash-jl/63075 "2021-06-17T14:34:27Z")

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Hello, I want to create an interactive GUI based on Dash.jl. in this GUI I want to plot an image and pick a pixel using the mouse. in Makie.jl this is strait forward issue, I found that WGLMakie.jl can pass the makie p…

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## [Doing strange things with DataTypes in functions](https://discourse.julialang.org/t/doing-strange-things-with-datatypes-in-functions/63086)

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**Author:** [@Impressium](https://discourse.julialang.org/u/Impressium)\
**Replies:** 5\
**Last updated:** [June 17, 2021, 2:21pm UTC](https://discourse.julialang.org/t/doing-strange-things-with-datatypes-in-functions/63086 "2021-06-17T14:21:15Z")

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Hey all :slight\_smile: Initially I wanted to do this: julia\> f{T}(i::T) = i ERROR: UndefVarError: T not defined Stacktrace: \[1\] top-level scope @ REPL\[51\]:1 But it only works for constructor of structs. Then I th…

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## [Oacle.jl use on windows](https://discourse.julialang.org/t/oacle-jl-use-on-windows/63088)

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**Author:** [@bww00](https://discourse.julialang.org/u/bww00)\
**Replies:** 0\
**Last updated:** [June 17, 2021, 1:50pm UTC](https://discourse.julialang.org/t/oacle-jl-use-on-windows/63088 "2021-06-17T13:50:36Z")

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We would like to use oracle.jl to on windows to access an oracle db on a different machine. Oracle.jl lists requirements of macos or linux. Is the a precompiled windows version floating around ? Thanks

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## [Opportunities at Invenia Labs](https://discourse.julialang.org/t/opportunities-at-invenia-labs/63087)

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**Author:** [@Invenia\_Robbie\_Smith](https://discourse.julialang.org/u/Invenia_Robbie_Smith)\
**Replies:** 0\
**Last updated:** [June 17, 2021, 1:46pm UTC](https://discourse.julialang.org/t/opportunities-at-invenia-labs/63087 "2021-06-17T13:46:43Z")

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Hi Julia community! Invenia Labs is a machine learning lab based in Cambridge, UK and Winnipeg, Manitoba. For more information about Invenia Labs generally, please visit Invenia For details about current opportunities…

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## [Allocations when passing closure as parameter](https://discourse.julialang.org/t/allocations-when-passing-closure-as-parameter/63082)

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**Author:** [@lmiq](https://discourse.julialang.org/u/lmiq)\
**Replies:** 2\
**Last updated:** [June 17, 2021, 1:13pm UTC](https://discourse.julialang.org/t/allocations-when-passing-closure-as-parameter/63082 "2021-06-17T13:13:04Z")

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I struggling to obtain a minimal working example. But I have one situation which looks like: function outer!(f::Function, output,x::AbstractVector) for i in 1:10 output = inner!(f,output,x) end return output …

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## [\[ANN\] DataFramesMeta 0.7.0 release](https://discourse.julialang.org/t/ann-dataframesmeta-0-7-0-release/63084)

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**Author:** [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)\
**Replies:** 0\
**Last updated:** [June 17, 2021, 12:45pm UTC](https://discourse.julialang.org/t/ann-dataframesmeta-0-7-0-release/63084 "2021-06-17T12:45:57Z")

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I am happy to announce a new release of DataFramesMeta. This new release contains three important additions @byrow. Being able to better work perform transformations by-row, rather than using broadcasting, has been a l…

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## [Basic string iteration](https://discourse.julialang.org/t/basic-string-iteration/63081)

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**Author:** [@alemelis](https://discourse.julialang.org/u/alemelis)\
**Replies:** 6\
**Last updated:** [June 17, 2021, 1:01pm UTC](https://discourse.julialang.org/t/basic-string-iteration/63081 "2021-06-17T13:01:33Z")

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Hello, I came across this iteration behaviour I don’t really grasp. I can define a string and iterate through it character-by-character as julia\> test\_string = "abc" "abc" julia\> for character in test\_string …

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## [Type instability with static matrices when full size not given?](https://discourse.julialang.org/t/type-instability-with-static-matrices-when-full-size-not-given/63079)

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**Author:** [@nabla](https://discourse.julialang.org/u/nabla)\
**Replies:** 4\
**Last updated:** [June 17, 2021, 12:45pm UTC](https://discourse.julialang.org/t/type-instability-with-static-matrices-when-full-size-not-given/63079 "2021-06-17T12:45:20Z")

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I ran across the following, very wierd situation: if I don’t specify the 4th parameter in a SMatrix (which is supposed to be computed as the product of the sizes, then the code slows down considerably. MWE: using Benchm…

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## [Makie display error when used with VideoIO](https://discourse.julialang.org/t/makie-display-error-when-used-with-videoio/62968)

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**Author:** [@Jake](https://discourse.julialang.org/u/Jake)\
**Replies:** 2\
**Last updated:** [June 17, 2021, 12:36pm UTC](https://discourse.julialang.org/t/makie-display-error-when-used-with-videoio/62968 "2021-06-17T12:36:28Z")

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I am trying to view some video images recorded as mp4 on a cell phone. I have loaded VideoIO and Makie along with the backend GLMakie. I am using Windows 10, Julia 1.6.1 and have tried restarting Julia a few times and …

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## [Julia, PiGPIO for Button control](https://discourse.julialang.org/t/julia-pigpio-for-button-control/49862)

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**Author:** [@Hub\_Spencer](https://discourse.julialang.org/u/Hub_Spencer)\
**Replies:** 4\
**Last updated:** [May 22, 2021, 2:39pm UTC](https://discourse.julialang.org/t/julia-pigpio-for-button-control/49862 "2021-05-22T14:39:55Z")

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I’m new to Julia and I’m just toying with the language on Raspberry Pi with the PiGPIO library. Is there doc on how to use the PiGPIO.callback function to monitor Edge transitions? I can see the method, but no examples…

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## [Atomic operations stop working when upgrading to CUDA.jl version 3.3](https://discourse.julialang.org/t/atomic-operations-stop-working-when-upgrading-to-cuda-jl-version-3-3/63041)

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**Author:** [@gatocor](https://discourse.julialang.org/u/gatocor)\
**Replies:** 4\
**Last updated:** [June 17, 2021, 9:41am UTC](https://discourse.julialang.org/t/atomic-operations-stop-working-when-upgrading-to-cuda-jl-version-3-3/63041 "2021-06-17T09:41:58Z")

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I am developing a library and using CUDA. Because of the new capabilities of CUDA 3.3, I decided to upgrate to Julia 1.6 and now all the test I run fail in kernels depending on atomic operations. I tried to make the mos…

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## [ModellingToolkit ODESystem definition throwing error](https://discourse.julialang.org/t/modellingtoolkit-odesystem-definition-throwing-error/63002)

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**Author:** [@ap2013](https://discourse.julialang.org/u/ap2013)\
**Replies:** 5\
**Last updated:** [June 17, 2021, 8:45am UTC](https://discourse.julialang.org/t/modellingtoolkit-odesystem-definition-throwing-error/63002 "2021-06-17T08:45:14Z")

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I am defining and ODESystem using ModellingToolkit and I am running into a problem in the definition of the equations. The code below is the function to define the ODESystem function connectFFFB\_Grad(plant, ref, pid, m…

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## [Static Vector with two different units](https://discourse.julialang.org/t/static-vector-with-two-different-units/63070)

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**Author:** [@Luapulu](https://discourse.julialang.org/u/Luapulu)\
**Replies:** 1\
**Last updated:** [June 17, 2021, 8:15am UTC](https://discourse.julialang.org/t/static-vector-with-two-different-units/63070 "2021-06-17T08:15:36Z")

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I’m working with DifferentialEquations.jl and I have a state vector in 6-dimensional phase space. I would like to work with units and static vectors but my issue is that the momentum part of the phase space vector has a …

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## [Why is the definition of Spherical coordinates in Julia strange](https://discourse.julialang.org/t/why-is-the-definition-of-spherical-coordinates-in-julia-strange/63015)

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**Author:** [@Dennis\_West](https://discourse.julialang.org/u/Dennis_West)\
**Replies:** 4\
**Last updated:** [June 17, 2021, 8:32am UTC](https://discourse.julialang.org/t/why-is-the-definition-of-spherical-coordinates-in-julia-strange/63015 "2021-06-17T08:32:02Z")

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Hey, I want to transform a point in a cartesian coordinate system to a spherical one. I am using the Package CoordinateTransformations. As I made my first steps with SphericalFromCartesian I noticed that, when writing …

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## [Managing local package and artifacts repository](https://discourse.julialang.org/t/managing-local-package-and-artifacts-repository/62922)

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**Author:** [@hros](https://discourse.julialang.org/u/hros)\
**Replies:** 2\
**Last updated:** [June 17, 2021, 7:58am UTC](https://discourse.julialang.org/t/managing-local-package-and-artifacts-repository/62922 "2021-06-17T07:58:28Z")

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I recently found out that my ~/.julia package was taking about 20GB I deleted the directory, and started afresh Are there any “best usage” tips for maintaining a lean ~/.julia directory?

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## [Evaluating the "for" condition](https://discourse.julialang.org/t/evaluating-the-for-condition/63050)

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**Author:** [@marllos](https://discourse.julialang.org/u/marllos)\
**Replies:** 10\
**Last updated:** [June 17, 2021, 7:35am UTC](https://discourse.julialang.org/t/evaluating-the-for-condition/63050 "2021-06-17T07:35:12Z")

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Hello everyone. The following simple example is just to ask the question: will Julia evaluate the length function 5 times? Thank you. function test() v = \[1,2,3,4,5\] for i = 1:length(v) println(v\[i\]) end end

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## [Programming with Julia interpreter](https://discourse.julialang.org/t/programming-with-julia-interpreter/63064)

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**Author:** [@Ralph\_Snyder1](https://discourse.julialang.org/u/Ralph_Snyder1)\
**Replies:** 6\
**Last updated:** [June 17, 2021, 6:45am UTC](https://discourse.julialang.org/t/programming-with-julia-interpreter/63064 "2021-06-17T06:45:19Z")

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Is it possible to provide a switch in Atom to allow the user to choose between code development with the Julia compiler and the interpreter? My conjecture is that there is a tradeoff between compile times and run-times, …

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## [Selectdim behaviour for arrays of dimension greater than 2](https://discourse.julialang.org/t/selectdim-behaviour-for-arrays-of-dimension-greater-than-2/52211)

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**Author:** [@OlivierHnt](https://discourse.julialang.org/u/OlivierHnt)\
**Replies:** 5\
**Last updated:** [June 1, 2021, 2:27pm UTC](https://discourse.julialang.org/t/selectdim-behaviour-for-arrays-of-dimension-greater-than-2/52211 "2021-06-01T14:27:45Z")

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I just noticed a type-instability with selectdim. Consider the function f(A) = selectdim(A, 1, 1) For a matrix, we have that the return type of f is a 1D SubArray (as expected): julia\> A = rand(2,2); julia\> @code\_war…

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## [The conflict of variables using @build\_constraint](https://discourse.julialang.org/t/the-conflict-of-variables-using-build-constraint/62998)

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**Author:** [@BYS](https://discourse.julialang.org/u/BYS)\
**Replies:** 7\
**Last updated:** [June 17, 2021, 1:58am UTC](https://discourse.julialang.org/t/the-conflict-of-variables-using-build-constraint/62998 "2021-06-17T01:58:19Z")

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Hi, If there are two models in my code model1=Model() @variable(model1,x\[1:5\]) model2=Model() @variable(model2,x\[1:5\]) If I use con=@build\_constraint(x\[1\]\<=1) the x\[1\] belongs to model1 or model2? Thanks in advance…

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## [Overloading Base.hash is 2x slower than an identical function](https://discourse.julialang.org/t/overloading-base-hash-is-2x-slower-than-an-identical-function/63058)

<div class="topic-metadata">

**Author:** [@odow](https://discourse.julialang.org/u/odow)\
**Replies:** 1\
**Last updated:** [June 17, 2021, 1:20am UTC](https://discourse.julialang.org/t/overloading-base-hash-is-2x-slower-than-an-identical-function/63058 "2021-06-17T01:20:55Z")

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Can anyone explain (or reproduce) the following? Why is the Base.hash version slower and why the allocation? julia\> using BenchmarkTools julia\> mutable struct Foo end julia\> struct Bar f::Foo x:…

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## [Problem with parameter estimation in a epidemiological model](https://discourse.julialang.org/t/problem-with-parameter-estimation-in-a-epidemiological-model/63043)

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**Author:** [@fepra](https://discourse.julialang.org/u/fepra)\
**Replies:** 6\
**Last updated:** [June 16, 2021, 11:36pm UTC](https://discourse.julialang.org/t/problem-with-parameter-estimation-in-a-epidemiological-model/63043 "2021-06-16T23:36:46Z")

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Hello, I’m new to Julia. I’m trying to estimate parameter of a system of differential equations for a epidemiological model. I can solve the system but i can’t fit the parameter to my data. function SEAIRD!(du, u, p, t) …

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## [Spawn task on thread after delay and fetch result later](https://discourse.julialang.org/t/spawn-task-on-thread-after-delay-and-fetch-result-later/63051)

<div class="topic-metadata">

**Author:** [@Christopher\_Fisher](https://discourse.julialang.org/u/Christopher_Fisher)\
**Replies:** 0\
**Last updated:** [June 16, 2021, 9:57pm UTC](https://discourse.julialang.org/t/spawn-task-on-thread-after-delay-and-fetch-result-later/63051 "2021-06-16T21:57:32Z")

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I am trying to execute a function on a different thread after a specified delay. I could use Timer, but I need to fetch the result. As shown below, my solution was to use sleep. I was wondering if this is there are bette…

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## [\[ANN\] COBREXA.jl: COnstraint-Based Reconstruction and EXa-scale Analysis in Julia](https://discourse.julialang.org/t/ann-cobrexa-jl-constraint-based-reconstruction-and-exa-scale-analysis-in-julia/63022)

<div class="topic-metadata">

**Author:** [@Elmo](https://discourse.julialang.org/u/Elmo)\
**Replies:** 2\
**Last updated:** [June 16, 2021, 7:43pm UTC](https://discourse.julialang.org/t/ann-cobrexa-jl-constraint-based-reconstruction-and-exa-scale-analysis-in-julia/63022 "2021-06-16T19:43:51Z")

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Large-scale mechanistic biological models present unique difficulties in terms of system identification and parameterization. Constraint-based reconstruction and analysis (COBRA) methods are a relatively recent developme…

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## [Having nothing as an outcome using GLPK and JuMP](https://discourse.julialang.org/t/having-nothing-as-an-outcome-using-glpk-and-jump/62948)

<div class="topic-metadata">

**Author:** [@marouane](https://discourse.julialang.org/u/marouane)\
**Replies:** 5\
**Last updated:** [June 16, 2021, 6:41pm UTC](https://discourse.julialang.org/t/having-nothing-as-an-outcome-using-glpk-and-jump/62948 "2021-06-16T18:41:19Z")

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i have this piece of code for optimization: using JuMP using GLPK function scan\_maker(A) m= Model(GLPK.Optimizer) level = size(A, 2) v = zeros(Int, level) ub = zeros(Int, level) lb = zeros(Int…

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## [Vscode-julia 1.2.4 fails with alt + enter execution (ctrl+enter works)](https://discourse.julialang.org/t/vscode-julia-1-2-4-fails-with-alt-enter-execution-ctrl-enter-works/62966)

<div class="topic-metadata">

**Author:** [@Steven\_Varga](https://discourse.julialang.org/u/Steven_Varga)\
**Replies:** 6\
**Last updated:** [June 16, 2021, 6:33pm UTC](https://discourse.julialang.org/t/vscode-julia-1-2-4-fails-with-alt-enter-execution-ctrl-enter-works/62966 "2021-06-16T18:33:00Z")

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update: tried the same setup with standard Julia 1.6.1 (as opposed to custom compile) and everything checks out. There should be something wrong with my Julia compile. On vscode 1.57.0 with julia 1.5.3 the ALT+ENTER exe…

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## [Suggestion violates cauality](https://discourse.julialang.org/t/suggestion-violates-cauality/62958)

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**Author:** [@Mark\_Nahabedian](https://discourse.julialang.org/u/Mark_Nahabedian)\
**Replies:** 4\
**Last updated:** [June 16, 2021, 6:30pm UTC](https://discourse.julialang.org/t/suggestion-violates-cauality/62958 "2021-06-16T18:30:49Z")

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Anyone seen this before: ERROR: LoadError: ArgumentError: Package Pkg not found in current path: - Run \`import Pkg; Pkg.add("Pkg")\` to install the Pkg package. Any ideas what I might have done to cause it? I’m using a…

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