# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=257

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**Page:** 258

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## [Building on OrdinaryDiffEq.jl vs DiffEqBase.jl](https://discourse.julialang.org/t/building-on-ordinarydiffeq-jl-vs-diffeqbase-jl/85620)

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**Author:** [@nathanaelbosch](https://discourse.julialang.org/u/nathanaelbosch)\
**Replies:** 3\
**Last updated:** [August 20, 2022, 11:36am UTC](https://discourse.julialang.org/t/building-on-ordinarydiffeq-jl-vs-diffeqbase-jl/85620 "2022-08-20T11:36:59Z")

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Hi everyone, I am curious about the best approach for implementing custom ODE solvers in the DifferentialEquations.jl ecosystem. As far as I know, there are mostly two options: Contributing to OrdinaryDiffEq.jl: Wh…

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## [Efficient calculation of block matrices with only the Linear Map given](https://discourse.julialang.org/t/efficient-calculation-of-block-matrices-with-only-the-linear-map-given/85814)

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**Author:** [@roflmaostc](https://discourse.julialang.org/u/roflmaostc)\
**Replies:** 4\
**Last updated:** [August 20, 2022, 11:31am UTC](https://discourse.julialang.org/t/efficient-calculation-of-block-matrices-with-only-the-linear-map-given/85814 "2022-08-20T11:31:31Z")

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Hi! I have the situation that I construct block matrices where I want to avoid to explicitly have them. For example, with Fourier transforms we can either use slow matrices or fast FFTs: using FFTW using LinearAlgebra…

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## [Optimization crashes Julia 1.8](https://discourse.julialang.org/t/optimization-crashes-julia-1-8/86050)

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**Author:** [@mzhenirovskyy](https://discourse.julialang.org/u/mzhenirovskyy)\
**Replies:** 1\
**Last updated:** [August 20, 2022, 2:48am UTC](https://discourse.julialang.org/t/optimization-crashes-julia-1-8/86050 "2022-08-20T02:48:42Z")

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The issue description is here: Does anybody see something like it? Any idea? Thanks!

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## [ByRow subset vs filter performance](https://discourse.julialang.org/t/byrow-subset-vs-filter-performance/86022)

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**Author:** [@hdavid16](https://discourse.julialang.org/u/hdavid16)\
**Replies:** 6\
**Last updated:** [August 19, 2022, 8:39pm UTC](https://discourse.julialang.org/t/byrow-subset-vs-filter-performance/86022 "2022-08-19T20:39:15Z")

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I just compared subset (using a :col =\> ByRow(==(0)) operation) vs filter (using a :col =\> ==(0) operation) on a DataFrame. In both cases, I set view=true and I see significantly less allocations when using filter vs whe…

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## [Playing/recording signals with PortAudio.jl](https://discourse.julialang.org/t/playing-recording-signals-with-portaudio-jl/85878)

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**Author:** [@Thomas\_Lei](https://discourse.julialang.org/u/Thomas_Lei)\
**Replies:** 3\
**Last updated:** [August 19, 2022, 6:46pm UTC](https://discourse.julialang.org/t/playing-recording-signals-with-portaudio-jl/85878 "2022-08-19T18:46:59Z")

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Hi all, I’m trying to use PortAudio.jl to stream and record audio signals. What I try to achieve is playing a signal through a loudspeaker and record this same signal through a mic. Basically, I want to record what I’m…

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## [How to seed the \`random\_layout\` in the GraphPlot package?](https://discourse.julialang.org/t/how-to-seed-the-random-layout-in-the-graphplot-package/86015)

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**Author:** [@math\_opt](https://discourse.julialang.org/u/math_opt)\
**Replies:** 1\
**Last updated:** [August 19, 2022, 3:46pm UTC](https://discourse.julialang.org/t/how-to-seed-the-random-layout-in-the-graphplot-package/86015 "2022-08-19T15:46:49Z")

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Can I seed the random\_layout when using the GraphPlot package to visualize a graph? For example: using GraphPlot using Graphs using Compose g = SimpleGraph() add\_vertices!(g,25) for i in 1:10 for j in 11:25 …

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## [CDF of a copula from Copulas.jl?](https://discourse.julialang.org/t/cdf-of-a-copula-from-copulas-jl/85786)

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**Author:** [@HJW019](https://discourse.julialang.org/u/HJW019)\
**Replies:** 24\
**Last updated:** [August 19, 2022, 2:41pm UTC](https://discourse.julialang.org/t/cdf-of-a-copula-from-copulas-jl/85786 "2022-08-19T14:41:15Z")

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I am experimenting with Copulas.jl to see if I could use it for my work. I am in general impressed. However, I found I could not get the CDF value from a joint distribution constructed by the copula. Getting the PDF valu…

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## [Lines on maps with PlotlyJS](https://discourse.julialang.org/t/lines-on-maps-with-plotlyjs/86000)

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**Author:** [@lgo](https://discourse.julialang.org/u/lgo)\
**Replies:** 1\
**Last updated:** [August 19, 2022, 1:54pm UTC](https://discourse.julialang.org/t/lines-on-maps-with-plotlyjs/86000 "2022-08-19T13:54:45Z")

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I want to use PlotlyJS to create lines on maps as explained here. I build on the maps example from the PlotlyJS documentation to “translate” the JavaScript code into the Julia/PlotlyJS notation, but the resulting map doe…

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## [Automatic differentiation with subset of parameters in ModelingToolkit](https://discourse.julialang.org/t/automatic-differentiation-with-subset-of-parameters-in-modelingtoolkit/85917)

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**Author:** [@Antomek](https://discourse.julialang.org/u/Antomek)\
**Replies:** 6\
**Last updated:** [August 19, 2022, 1:01pm UTC](https://discourse.julialang.org/t/automatic-differentiation-with-subset-of-parameters-in-modelingtoolkit/85917 "2022-08-19T13:01:09Z")

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Hello, I am building a large ODESystem using ModelingToolkit, on which I’d like to use automatic differentiation. Because it is large, there are many parameters, resulting from the many subsystems. However, I want to…

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## [How to increase the vertical gap between subplots in Plots.jl](https://discourse.julialang.org/t/how-to-increase-the-vertical-gap-between-subplots-in-plots-jl/85990)

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**Author:** [@Firstname\_Lastname](https://discourse.julialang.org/u/Firstname_Lastname)\
**Replies:** 2\
**Last updated:** [August 19, 2022, 10:11am UTC](https://discourse.julialang.org/t/how-to-increase-the-vertical-gap-between-subplots-in-plots-jl/85990 "2022-08-19T10:11:13Z")

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I have four subplots using MonteCarloMeasurements, Plots x = LinRange(1:0.1:3) a = 1 \\pm 0.1 b = 2 \\pm 0.3 f(x) = a\*x + b fig1 = plot(x, f.(x)) fig2 = plot(x, f.(x)) fig3 = plot(x, f.(x)) fig4 = plot(x, f.(x)) They…

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## [Inverse of symbolic matrix](https://discourse.julialang.org/t/inverse-of-symbolic-matrix/85764)

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**Author:** [@qwerty](https://discourse.julialang.org/u/qwerty)\
**Replies:** 27\
**Last updated:** [August 19, 2022, 9:32am UTC](https://discourse.julialang.org/t/inverse-of-symbolic-matrix/85764 "2022-08-19T09:32:52Z")

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using Symbolics, LinearAlgebra @variables q::Real iden = collect(I(4) .\* 1.0) k = inv(iden .\* q^2) I get true/q^2 on the diagonal instead of 1/q^2

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## [DataFrames.jl vcat column data from different rows](https://discourse.julialang.org/t/dataframes-jl-vcat-column-data-from-different-rows/85809)

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**Author:** [@ethomag](https://discourse.julialang.org/u/ethomag)\
**Replies:** 11\
**Last updated:** [August 19, 2022, 5:57am UTC](https://discourse.julialang.org/t/dataframes-jl-vcat-column-data-from-different-rows/85809 "2022-08-19T05:57:31Z")

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I have a number of networks packets with sampled data, that is fragmented and was wondering whether de-fragmentation can be done with DataFrames or if I have to pre-process the data first ? sort!(df, \[:frame, :subframe,…

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## [Catalyst.jl compositions with parameters as stoichiometric constants](https://discourse.julialang.org/t/catalyst-jl-compositions-with-parameters-as-stoichiometric-constants/85934)

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**Author:** [@snystrom](https://discourse.julialang.org/u/snystrom)\
**Replies:** 4\
**Last updated:** [August 19, 2022, 2:36am UTC](https://discourse.julialang.org/t/catalyst-jl-compositions-with-parameters-as-stoichiometric-constants/85934 "2022-08-19T02:36:47Z")

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I am trying to build a set of reaction models that I can compose together using Catalyst.jl, but running into a small problem. Say I want to model a system and include stoichiometric terms as parameters. For instance, t…

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## [DiffEqParamEstim with Modellingtoolkit](https://discourse.julialang.org/t/diffeqparamestim-with-modellingtoolkit/85788)

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**Author:** [@xztt](https://discourse.julialang.org/u/xztt)\
**Replies:** 11\
**Last updated:** [August 19, 2022, 2:22am UTC](https://discourse.julialang.org/t/diffeqparamestim-with-modellingtoolkit/85788 "2022-08-19T02:22:52Z")

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Hi I am generating a model using MTK and would like to generate a simple loss function for it. Is there a way in which I can access the observed variables in my solution when solving my problem. I know given a standar…

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## [Time it takes to multiply two floats](https://discourse.julialang.org/t/time-it-takes-to-multiply-two-floats/85933)

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**Author:** [@JUAN\_CARLOS\_GALVIS\_A](https://discourse.julialang.org/u/JUAN_CARLOS_GALVIS_A)\
**Replies:** 2\
**Last updated:** [August 18, 2022, 6:09pm UTC](https://discourse.julialang.org/t/time-it-takes-to-multiply-two-floats/85933 "2022-08-18T18:09:31Z")

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When i benchmark the multiplication of two Float16, compared to the multiplication of two Float64, it seems it takes the same time. Is this right?

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## [AMDGPU.jl has made such amazing progress over the last year!](https://discourse.julialang.org/t/amdgpu-jl-has-made-such-amazing-progress-over-the-last-year/75333)

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**Author:** [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Replies:** 16\
**Last updated:** [August 18, 2022, 2:43pm UTC](https://discourse.julialang.org/t/amdgpu-jl-has-made-such-amazing-progress-over-the-last-year/75333 "2022-08-18T14:43:07Z")

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I tried AMDGPU.jl last year for my 580 Radeon GPU and it was a chore to set everything up, even for a competent sysadmin. I tried it today, and I am amazed how great it is! I have a moderately recent Linux kernel (update…

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## [Automatically generated API and Frontend for a JuMP model](https://discourse.julialang.org/t/automatically-generated-api-and-frontend-for-a-jump-model/85333)

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**Author:** [@merrickj](https://discourse.julialang.org/u/merrickj)\
**Replies:** 4\
**Last updated:** [August 18, 2022, 10:28am UTC](https://discourse.julialang.org/t/automatically-generated-api-and-frontend-for-a-jump-model/85333 "2022-08-18T10:28:37Z")

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Dear JuMP community, We would like to share with you MOS, software that automatically generates an API and Frontend for an annotated optimization model: MOS Software Documentation — MOS documentation There are instruct…

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## [What is the optimised way to find connected components in a graph with edge weights greater than zero?](https://discourse.julialang.org/t/what-is-the-optimised-way-to-find-connected-components-in-a-graph-with-edge-weights-greater-than-zero/85902)

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**Author:** [@Manu\_Francis](https://discourse.julialang.org/u/Manu_Francis)\
**Replies:** 4\
**Last updated:** [August 18, 2022, 5:37am UTC](https://discourse.julialang.org/t/what-is-the-optimised-way-to-find-connected-components-in-a-graph-with-edge-weights-greater-than-zero/85902 "2022-08-18T05:37:16Z")

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Hi I am trying to find the connected components of a simple weighted graph with edge weights having a value greater than zero as below. using Graphs using SimpleWeightedGraphs len = 105\_000 g = SimpleWeighted…

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## [Generate Variables JuMP](https://discourse.julialang.org/t/generate-variables-jump/85900)

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**Author:** [@Yuri\_Mizusawa](https://discourse.julialang.org/u/Yuri_Mizusawa)\
**Replies:** 3\
**Last updated:** [August 18, 2022, 1:58am UTC](https://discourse.julialang.org/t/generate-variables-jump/85900 "2022-08-18T01:58:07Z")

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Hi, I’m not sure if I had to make a new post or continue the old one, but as I have a new question I created a new topic. I am solving an optimization problem with jump using the following table: Row │ time room\_1 …

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## [JuMP @Variable](https://discourse.julialang.org/t/jump-variable/85853)

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**Author:** [@Yuri\_Mizusawa](https://discourse.julialang.org/u/Yuri_Mizusawa)\
**Replies:** 2\
**Last updated:** [August 17, 2022, 11:05pm UTC](https://discourse.julialang.org/t/jump-variable/85853 "2022-08-17T23:05:15Z")

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Hi, I am solving an optimization problem with jump using the following table: Row │ time room\_1 room\_2 room\_3 w\_day │ Float64 Float64 Float64 Float64 String ─────┼────────────────────────────────…

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## [How is Optim.jl's IPNewton so good compared to (exponentiated) gradient descent?](https://discourse.julialang.org/t/how-is-optim-jls-ipnewton-so-good-compared-to-exponentiated-gradient-descent/85685)

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**Author:** [@ForceBru](https://discourse.julialang.org/u/ForceBru)\
**Replies:** 4\
**Last updated:** [August 17, 2022, 9:27pm UTC](https://discourse.julialang.org/t/how-is-optim-jls-ipnewton-so-good-compared-to-exponentiated-gradient-descent/85685 "2022-08-17T21:27:45Z")

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This question is about implementing an optimization algorithm in Julia and comparing it with IPNewton from Optim.jl. It’s kind of broad, so not sure if it fits here. Let me know if it doesn’t. I wrote some code to minim…

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## [Plots.jl with PGFPlotsX adds series in the wrong order](https://discourse.julialang.org/t/plots-jl-with-pgfplotsx-adds-series-in-the-wrong-order/85896)

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**Author:** [@Joseph\_Bradley](https://discourse.julialang.org/u/Joseph_Bradley)\
**Replies:** 2\
**Last updated:** [August 17, 2022, 9:23pm UTC](https://discourse.julialang.org/t/plots-jl-with-pgfplotsx-adds-series-in-the-wrong-order/85896 "2022-08-17T21:23:17Z")

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In Plots.jl, the PGFPlotsX backend won’t let me add another series with proper control over the z-order. Here is the MWE: using Plots pgfplotsx() input = range(0, 4π, 100) output = cos.(input) plt = scatter(input, out…

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## [How to scale the axes in Makie subplots?](https://discourse.julialang.org/t/how-to-scale-the-axes-in-makie-subplots/85881)

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**Author:** [@math\_opt](https://discourse.julialang.org/u/math_opt)\
**Replies:** 2\
**Last updated:** [August 17, 2022, 5:51pm UTC](https://discourse.julialang.org/t/how-to-scale-the-axes-in-makie-subplots/85881 "2022-08-17T17:51:56Z")

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When I create subplots, the y-axis is usually taller than the x-axis. I want them to be of same (or at least similar) length. For example, the following code produces: using CairoMakie function plot() f= Figure() …

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## [Want to learn Reinforcement Learning from scratch for mini-project](https://discourse.julialang.org/t/want-to-learn-reinforcement-learning-from-scratch-for-mini-project/85836)

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**Author:** [@Lighfe](https://discourse.julialang.org/u/Lighfe)\
**Replies:** 6\
**Last updated:** [August 17, 2022, 1:30pm UTC](https://discourse.julialang.org/t/want-to-learn-reinforcement-learning-from-scratch-for-mini-project/85836 "2022-08-17T13:30:03Z")

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Hello everyone, I’m quite new to Julia but have some basic knowledge of other programming languages. As a project for myself I want to train an RL algorithm for a boardgame. It’s a push-your-luck type of game, where yo…

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## [Create a function of derivatives in Symbolics.jl](https://discourse.julialang.org/t/create-a-function-of-derivatives-in-symbolics-jl/85808)

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**Author:** [@Albert\_Zevelev](https://discourse.julialang.org/u/Albert_Zevelev)\
**Replies:** 5\
**Last updated:** [August 17, 2022, 1:20pm UTC](https://discourse.julialang.org/t/create-a-function-of-derivatives-in-symbolics-jl/85808 "2022-08-17T13:20:21Z")

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I have a function f(x,u;p) where x, u are both vectors of variables and p is a vector of parameters. I would like to create a new function f\_{x}(x,u;p) = \\frac{\\partial f}{ \\partial x} and f\_{xu}(x,u;p) = \\frac{\\partial…

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## [Best way to take derivatives of unevenly spaced data (with interpolations? discrete derivatives?)](https://discourse.julialang.org/t/best-way-to-take-derivatives-of-unevenly-spaced-data-with-interpolations-discrete-derivatives/54097)

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**Author:** [@CosmoProf](https://discourse.julialang.org/u/CosmoProf)\
**Replies:** 37\
**Last updated:** [April 30, 2021, 12:44pm UTC](https://discourse.julialang.org/t/best-way-to-take-derivatives-of-unevenly-spaced-data-with-interpolations-discrete-derivatives/54097 "2021-04-30T12:44:34Z")

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Hi, I have a function f(t), where f is numerically sampled at discrete points in time t that are NOT evenly sampled in time. (This is unavoidable.) I need to take the first and second derivatives of f(t), compute a comp…

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## [Makie - tricontourf from matplotlib in Makie](https://discourse.julialang.org/t/makie-tricontourf-from-matplotlib-in-makie/77685)

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**Author:** [@cmarcotte](https://discourse.julialang.org/u/cmarcotte)\
**Replies:** 13\
**Last updated:** [August 17, 2022, 12:06pm UTC](https://discourse.julialang.org/t/makie-tricontourf-from-matplotlib-in-makie/77685 "2022-08-17T12:06:06Z")

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Hi everyone, I am trying to get something like tricontourf from matplotlib to work in Makie. The heatmap with three vector inputs example here is the closest I can find in the documentation, but there’s no obvious way t…

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## [Symbolics Einstein notation](https://discourse.julialang.org/t/symbolics-einstein-notation/85866)

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**Author:** [@qwerty](https://discourse.julialang.org/u/qwerty)\
**Replies:** 1\
**Last updated:** [August 17, 2022, 9:19am UTC](https://discourse.julialang.org/t/symbolics-einstein-notation/85866 "2022-08-17T09:19:41Z")

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How do I do this with the arrayop macro in Symbolics.jl? using Tullio, Symbolics @variables x₀ q = x₀\*rand(4, 4) t = x₀\*rand(4, 4, 4) @tullio r\[a, b, c\] := q\[a, i\]\*t\[i, b, c\] I tried this r = Symbolics.@arrayop (a, …

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## [Which library supports a non-allocating neural network model](https://discourse.julialang.org/t/which-library-supports-a-non-allocating-neural-network-model/85591)

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**Author:** [@jmair](https://discourse.julialang.org/u/jmair)\
**Replies:** 13\
**Last updated:** [August 17, 2022, 8:51am UTC](https://discourse.julialang.org/t/which-library-supports-a-non-allocating-neural-network-model/85591 "2022-08-17T08:51:10Z")

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Hi all, I have been using Flux.jl to create a simple model. I do not need to take gradients; I only need to evaluate a loss for a given set of parameters. Currently I use a setup similiar to this: using BenchmarkTools …

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## [How to correctly track optimization loss value with callback using particle swarm?](https://discourse.julialang.org/t/how-to-correctly-track-optimization-loss-value-with-callback-using-particle-swarm/85799)

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**Author:** [@thompsonmj](https://discourse.julialang.org/u/thompsonmj)\
**Replies:** 1\
**Last updated:** [August 17, 2022, 4:02am UTC](https://discourse.julialang.org/t/how-to-correctly-track-optimization-loss-value-with-callback-using-particle-swarm/85799 "2022-08-17T04:02:30Z")

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I’d like to track loss values in a particle swarm optimization with a callback, but I’m not sure where exactly the loss numbers being tracked in the callback are coming from. Comparing the trace printed by the optimizer…

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