# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1453

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

**Page:** 1454

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## [3D camera movements in Makie](https://discourse.julialang.org/t/3d-camera-movements-in-makie/57530)

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**Author:** [@weymouth](https://discourse.julialang.org/u/weymouth)\
**Replies:** 3\
**Last updated:** [March 19, 2021, 3:17pm UTC](https://discourse.julialang.org/t/3d-camera-movements-in-makie/57530 "2021-03-19T15:17:26Z")

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Are there any examples for 3D camera movements using the new Figure() set up for Makie and GLMakie?

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## [Using @warn like @assert?](https://discourse.julialang.org/t/using-warn-like-assert/57545)

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**Author:** [@markmbaum](https://discourse.julialang.org/u/markmbaum)\
**Replies:** 1\
**Last updated:** [March 19, 2021, 2:56pm UTC](https://discourse.julialang.org/t/using-warn-like-assert/57545 "2021-03-19T14:56:28Z")

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Short question! Is there a way to conditionally produce a warning without writing the if-end block? It would look like @warn x \< y "you should know that x is less than y" similar to the way that @assert works.

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## [Bottom banner in dark mode is not dark](https://discourse.julialang.org/t/bottom-banner-in-dark-mode-is-not-dark/47839)

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**Author:** [@thofma](https://discourse.julialang.org/u/thofma)\
**Replies:** 3\
**Last updated:** [March 19, 2021, 2:23pm UTC](https://discourse.julialang.org/t/bottom-banner-in-dark-mode-is-not-dark/47839 "2021-03-19T14:23:55Z")

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Either I never scrolled this far or this is new, but lately I have noticed that the bottom banner in dark mode is not dark, but white. This looks very odd.

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## [Constant linear equation d/dt x=Ax with DifferentialEquations.jl](https://discourse.julialang.org/t/constant-linear-equation-d-dt-x-ax-with-differentialequations-jl/57532)

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**Author:** [@jamblejoe](https://discourse.julialang.org/u/jamblejoe)\
**Replies:** 4\
**Last updated:** [March 19, 2021, 12:57pm UTC](https://discourse.julialang.org/t/constant-linear-equation-d-dt-x-ax-with-differentialequations-jl/57532 "2021-03-19T12:57:31Z")

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In Non-autonomous Linear ODE / Lie Group ODE Solvers · DifferentialEquations.jl are examples for solving d/dt x = A(t) x, time-dependent A, or state dependent A(x), d/dt x = A(x)x, but no example for just constant A. How…

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## [How to eliminate empty columns](https://discourse.julialang.org/t/how-to-eliminate-empty-columns/57484)

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**Author:** [@Laco\_Kovac](https://discourse.julialang.org/u/Laco_Kovac)\
**Replies:** 4\
**Last updated:** [March 19, 2021, 12:36pm UTC](https://discourse.julialang.org/t/how-to-eliminate-empty-columns/57484 "2021-03-19T12:36:22Z")

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Here is roughly the code which exports data from the table to CSV String using LibPQ, DataFrames, CSV executeResult = execute(conn, "SELECT c1, c2, c3, c4, c5 FROM some\_table WHERE some\_id = '$someId'") if (LibPQ.libpq…

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## [Convert png image into base64 string?](https://discourse.julialang.org/t/convert-png-image-into-base64-string/57515)

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**Author:** [@Ravinder\_Ram](https://discourse.julialang.org/u/Ravinder_Ram)\
**Replies:** 1\
**Last updated:** [March 19, 2021, 12:21pm UTC](https://discourse.julialang.org/t/convert-png-image-into-base64-string/57515 "2021-03-19T12:21:08Z")

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how to convert png image into base64 string and vice versa?

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## [Searching for a simple polynomial curve fitting example](https://discourse.julialang.org/t/searching-for-a-simple-polynomial-curve-fitting-example/5302)

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**Author:** [@J\_T](https://discourse.julialang.org/u/J_T)\
**Replies:** 6\
**Last updated:** [March 19, 2021, 5:10am UTC](https://discourse.julialang.org/t/searching-for-a-simple-polynomial-curve-fitting-example/5302 "2021-03-19T05:10:51Z")

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Im new to mathematical optimisation, so I’m looking for a simple example I can learn from … My (initial) problem looks like 1000 cartesian points in Float16 I want to find a polynomial p(x) (to be evaluated in Float16…

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## [\[ANN\]: InteractBase, a redesign of Interact to create and style web apps in Julia](https://discourse.julialang.org/t/ann-interactbase-a-redesign-of-interact-to-create-and-style-web-apps-in-julia/11471)

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**Author:** [@piever](https://discourse.julialang.org/u/piever)\
**Replies:** 2\
**Last updated:** [March 19, 2021, 11:29am UTC](https://discourse.julialang.org/t/ann-interactbase-a-redesign-of-interact-to-create-and-style-web-apps-in-julia/11471 "2021-03-19T11:29:51Z")

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I’m happy to announce the InteractBase, InteractBulma and InteractUIkit packages, to build interactive HTML5 widgets in Julia (InteractBulma and InteractUIkit are used to add “styling” to the widgets, using the Bulma or U…

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## [JSON.jl output undecorated/unquoted string](https://discourse.julialang.org/t/json-jl-output-undecorated-unquoted-string/57527)

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**Author:** [@essenciary](https://discourse.julialang.org/u/essenciary)\
**Replies:** 2\
**Last updated:** [March 19, 2021, 10:15am UTC](https://discourse.julialang.org/t/json-jl-output-undecorated-unquoted-string/57527 "2021-03-19T10:15:41Z")

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Hi, I have a singleton type Undefined which is meant to match JavaScript’s undefined primitive. As such, when JSON rendered, this should output as undefined instead of the default "undefined" (not wrapped in double quot…

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## [Conditional use of VSCode plot pane in \`Base.show\`?](https://discourse.julialang.org/t/conditional-use-of-vscode-plot-pane-in-base-show/57520)

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**Author:** [@korsbo](https://discourse.julialang.org/u/korsbo)\
**Replies:** 5\
**Last updated:** [March 19, 2021, 9:23am UTC](https://discourse.julialang.org/t/conditional-use-of-vscode-plot-pane-in-base-show/57520 "2021-03-19T09:23:07Z")

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Hi, I have a type that can usually, but not always, be displayed nicely (through Latexify) in the VSCode plot pane. I can use conditionals/error handling in my Base.show(::IO, ::MIME"juliavscode/html", ::MyType) overload…

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## [Hey, does anybody know why a generator does allocate memory while an iterator does](https://discourse.julialang.org/t/hey-does-anybody-know-why-a-generator-does-allocate-memory-while-an-iterator-does/57504)

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**Author:** [@BridgeBot](https://discourse.julialang.org/u/BridgeBot)\
**Replies:** 1\
**Last updated:** [March 19, 2021, 9:00am UTC](https://discourse.julialang.org/t/hey-does-anybody-know-why-a-generator-does-allocate-memory-while-an-iterator-does/57504 "2021-03-19T09:00:49Z")

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Hey, does anybody know why a generator does allocate memory while an iterator doesn’t when assigned to an existing location? julia&gt; x = randn((1000)); julia&gt; y = 1:1000 1:1000 julia&gt; g = (i for i=1:1000) Base…

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## [Discrete event simulation framework for discrete time](https://discourse.julialang.org/t/discrete-event-simulation-framework-for-discrete-time/55436)

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**Author:** [@manuka](https://discourse.julialang.org/u/manuka)\
**Replies:** 4\
**Last updated:** [March 19, 2021, 8:56am UTC](https://discourse.julialang.org/t/discrete-event-simulation-framework-for-discrete-time/55436 "2021-03-19T08:56:57Z")

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I would like to receive feedback on my simulation model. I have posted it in codereview.stackexchange but recieved almost no feedback (Discrete event simulation framework for discrete times in Julia - Code Review Stack E…

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## [Plots... with Dates along abscissa axis?](https://discourse.julialang.org/t/plots-with-dates-along-abscissa-axis/24454)

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**Author:** [@BLI](https://discourse.julialang.org/u/BLI)\
**Replies:** 7\
**Last updated:** [March 19, 2021, 8:52am UTC](https://discourse.julialang.org/t/plots-with-dates-along-abscissa-axis/24454 "2021-03-19T08:52:31Z")

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I have some data where I want to plot some quantity (ordinate) against dates (abscissa). The abscissa data are in Dates.Date() format. When plotting (I tested Plots with unicodeplots back-end), the dates are given in sec…

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## [How to parse/convert integers in DataFrame to float numbers](https://discourse.julialang.org/t/how-to-parse-convert-integers-in-dataframe-to-float-numbers/57507)

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**Author:** [@oo92](https://discourse.julialang.org/u/oo92)\
**Replies:** 30\
**Last updated:** [March 19, 2021, 6:54am UTC](https://discourse.julialang.org/t/how-to-parse-convert-integers-in-dataframe-to-float-numbers/57507 "2021-03-19T06:54:40Z")

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Hi. I am a beginner in Julia. I am trying to get data from a single row and perform statistics on it like taking the mean, median, etc. However, the error I am getting is telling me that I am trying to perform calculati…

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## [Can't use sort help, Here is code](https://discourse.julialang.org/t/cant-use-sort-help-here-is-code/57517)

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**Author:** [@Nitish\_Dubey](https://discourse.julialang.org/u/Nitish_Dubey)\
**Replies:** 2\
**Last updated:** [March 19, 2021, 6:48am UTC](https://discourse.julialang.org/t/cant-use-sort-help-here-is-code/57517 "2021-03-19T06:48:46Z")

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a = \[7 0 4 6 2 3 9\] 1×7 Array{Int64,2}: 7 0 4 6 2 3 9 julia\> sort(a) ERROR: UndefKeywordError: keyword argument dims not assigned Stacktrace: \[1\] sort(::Array{Int64,2}) at .\\sort.jl:1045 \[2\] top-level scope at…

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## [How to speed up this DataFrame operation](https://discourse.julialang.org/t/how-to-speed-up-this-dataframe-operation/57505)

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**Author:** [@amrods](https://discourse.julialang.org/u/amrods)\
**Replies:** 11\
**Last updated:** [March 19, 2021, 6:11am UTC](https://discourse.julialang.org/t/how-to-speed-up-this-dataframe-operation/57505 "2021-03-19T06:11:08Z")

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I have a DataFrame and I would like to store the data in an Array. This constructs the DataFrame: using DataFrames using DataFramesMeta using StatsBase n = 9^2\*2^2\*6^2\*42 const df = crossjoin( DataFram…

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## [How to do an operation like object.method() in Python](https://discourse.julialang.org/t/how-to-do-an-operation-like-object-method-in-python/57445)

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**Author:** [@zhangqian](https://discourse.julialang.org/u/zhangqian)\
**Replies:** 2\
**Last updated:** [March 19, 2021, 5:47am UTC](https://discourse.julialang.org/t/how-to-do-an-operation-like-object-method-in-python/57445 "2021-03-19T05:47:24Z")

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I am currently using Julia to do some fluid computation. Since I want to see the influence of some variables, like time steps, I need to store and prepare other persistent variables at first, and then pass the variable I…

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## [Garbage collector, C malloc and performance](https://discourse.julialang.org/t/garbage-collector-c-malloc-and-performance/57320)

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**Author:** [@KZiemian](https://discourse.julialang.org/u/KZiemian)\
**Replies:** 2\
**Last updated:** [March 19, 2021, 5:40am UTC](https://discourse.julialang.org/t/garbage-collector-c-malloc-and-performance/57320 "2021-03-19T05:40:50Z")

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I recently read very old blog post by Joel Spolsky Back to Basics from 2002 (side effect of reading about floating-point numbers, you know how this work). He stated that C code that use malloc can suffer for problems ver…

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## [Macro for generating struct](https://discourse.julialang.org/t/macro-for-generating-struct/57479)

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**Author:** [@Philippe\_Maincon1](https://discourse.julialang.org/u/Philippe_Maincon1)\
**Replies:** 4\
**Last updated:** [March 19, 2021, 5:40am UTC](https://discourse.julialang.org/t/macro-for-generating-struct/57479 "2021-03-19T05:40:00Z")

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I have written a macro that generates a new struct. It all works as intended when I test the macro from the REPL or from a script. Then of course, I want to call the macro in a function that does some cooking and retur…

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## [Hugely different solutions between JuMP/Ipopt and a commercial solver](https://discourse.julialang.org/t/hugely-different-solutions-between-jump-ipopt-and-a-commercial-solver/57218)

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**Author:** [@askvorts](https://discourse.julialang.org/u/askvorts)\
**Replies:** 4\
**Last updated:** [March 19, 2021, 12:34am UTC](https://discourse.julialang.org/t/hugely-different-solutions-between-jump-ipopt-and-a-commercial-solver/57218 "2021-03-19T00:34:34Z")

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I am using a commom portfolio optimization problem (maximizing the Sharpe ratio) to improve my knowledge of non-linear optimization using JuMP and Ipopt. The objective is Max pmean' w / sqrt(w' pcov w) subject to bound a…

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## [A precise definition of what it means to be an instance of an abstract type](https://discourse.julialang.org/t/a-precise-definition-of-what-it-means-to-be-an-instance-of-an-abstract-type/57270)

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**Author:** [@path-doc](https://discourse.julialang.org/u/path-doc)\
**Replies:** 42\
**Last updated:** [March 18, 2021, 11:32pm UTC](https://discourse.julialang.org/t/a-precise-definition-of-what-it-means-to-be-an-instance-of-an-abstract-type/57270 "2021-03-18T23:32:39Z")

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This question builds on What is difference between Type{T} and T - #16 by Henrique\_Becker Are there any objections to the definition below? Based on the following two quotes from Types · The Julia Language One partic…

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## [Writing tests in VS Code: workflow, autocomplete, and tooltips](https://discourse.julialang.org/t/writing-tests-in-vs-code-workflow-autocomplete-and-tooltips/57488)

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**Author:** [@tpgillam](https://discourse.julialang.org/u/tpgillam)\
**Replies:** 8\
**Last updated:** [March 18, 2021, 9:41pm UTC](https://discourse.julialang.org/t/writing-tests-in-vs-code-workflow-autocomplete-and-tooltips/57488 "2021-03-18T21:41:26Z")

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Hello all! I’m currently writing a package for the purpose of learning Julia, and am finding that autocomplete & hover-tooltips for types defined in the package do not seem to appear when in a test file. Problem Speci…

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## [How to propagate @inbounds properly](https://discourse.julialang.org/t/how-to-propagate-inbounds-properly/57487)

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**Author:** [@Uroc327](https://discourse.julialang.org/u/Uroc327)\
**Replies:** 8\
**Last updated:** [March 18, 2021, 8:47pm UTC](https://discourse.julialang.org/t/how-to-propagate-inbounds-properly/57487 "2021-03-18T20:47:08Z")

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I have a bunch of more or less complex functions that have arrays and indices as arguments. I’d like to specify @inbounds once at the top-level function and propagate this down through all nested and standalone functions…

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## [Performance disadvantages of structs?](https://discourse.julialang.org/t/performance-disadvantages-of-structs/57397)

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**Author:** [@Ribeiro](https://discourse.julialang.org/u/Ribeiro)\
**Replies:** 19\
**Last updated:** [March 18, 2021, 7:45pm UTC](https://discourse.julialang.org/t/performance-disadvantages-of-structs/57397 "2021-03-18T19:45:31Z")

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Hello, I have a lot of large arrays (matrices of floats, vectors of floats, vectors of StaticArrays of floats, vectors of StaticArrays of ints) in my code and calling functions is becoming cumbersome, as I have way too …

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## [Save additional quantities using DifferentialEquations.jl pkg](https://discourse.julialang.org/t/save-additional-quantities-using-differentialequations-jl-pkg/34011)

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**Author:** [@moesphere](https://discourse.julialang.org/u/moesphere)\
**Replies:** 26\
**Last updated:** [March 18, 2021, 7:44pm UTC](https://discourse.julialang.org/t/save-additional-quantities-using-differentialequations-jl-pkg/34011 "2021-03-18T19:44:25Z")

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Within my ODE function additional quantities are calculated which I would like to save to extract them later for e.g. inspection or plotting. There is the approach with the SavingCallback; however, the save\_func(u, t, i…

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## [Expression manipulation in Symbolics](https://discourse.julialang.org/t/expression-manipulation-in-symbolics/57486)

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**Author:** [@klaff](https://discourse.julialang.org/u/klaff)\
**Replies:** 4\
**Last updated:** [March 18, 2021, 7:05pm UTC](https://discourse.julialang.org/t/expression-manipulation-in-symbolics/57486 "2021-03-18T19:05:54Z")

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Playing with Symbolics like so: julia\> @variables a b c (a, b, c) julia\> par(x,y) = 1/(1/x+1/y) par (generic function with 1 method) julia\> ex1 = par(a, par(b,c)) (a^-1 + ((b^-1 + c^-1)^-1)^-1)^-1 julia\> simplify(ex1…

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## [Counting How Many Times a Point Passes Through a Grid of Coordinates](https://discourse.julialang.org/t/counting-how-many-times-a-point-passes-through-a-grid-of-coordinates/57229)

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**Author:** [@PJoynt](https://discourse.julialang.org/u/PJoynt)\
**Replies:** 4\
**Last updated:** [March 18, 2021, 6:49pm UTC](https://discourse.julialang.org/t/counting-how-many-times-a-point-passes-through-a-grid-of-coordinates/57229 "2021-03-18T18:49:45Z")

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Hi Everyone, I am currently trying to figure out how to count the number of times an object passes through each grid point defined by a set of coordinates. My grid is defined by x-coordinates and y-coordinates as: long…

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## [How to debug IDA](https://discourse.julialang.org/t/how-to-debug-ida/54643)

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**Author:** [@ohmsweetohm1](https://discourse.julialang.org/u/ohmsweetohm1)\
**Replies:** 1\
**Last updated:** [March 18, 2021, 6:26pm UTC](https://discourse.julialang.org/t/how-to-debug-ida/54643 "2021-03-18T18:26:07Z")

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I have a large DAE problem (102 variables) and have trouble finding consistent initial conditions. I always get: \[IDAS ERROR\] IDACalcIC Newton/Linesearch algorithm failed to converge. Is there a way to debug this?

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## [Optimizing the calculation of many distances](https://discourse.julialang.org/t/optimizing-the-calculation-of-many-distances/57343)

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**Author:** [@jsbyrnes](https://discourse.julialang.org/u/jsbyrnes)\
**Replies:** 28\
**Last updated:** [March 18, 2021, 5:11pm UTC](https://discourse.julialang.org/t/optimizing-the-calculation-of-many-distances/57343 "2021-03-18T17:11:08Z")

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Hey everyone, I’m translating some code from Julia to MATLAB and I have a seismic imaging program that now works in Julia and is a bit faster than MATLAB - but not a ton. The profiler says that the function pasted below …

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## [Confused about categories](https://discourse.julialang.org/t/confused-about-categories/57447)

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**Author:** [@TheLateKronos](https://discourse.julialang.org/u/TheLateKronos)\
**Replies:** 7\
**Last updated:** [March 18, 2021, 4:05pm UTC](https://discourse.julialang.org/t/confused-about-categories/57447 "2021-03-18T16:05:09Z")

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Tooling, Domains, Usage. I am not sure which category should be used when I have a questions reguarding some specific Package. Is it one of these, or would it be a good idea to add a new Packages category?

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