# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=363

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

**Page:** 364

---

## [How to train/predict a very simple feed-forward neural network in Flux?](https://discourse.julialang.org/t/how-to-train-predict-a-very-simple-feed-forward-neural-network-in-flux/39534)

<div class="topic-metadata">

**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 6\
**Last updated:** [May 26, 2021, 8:42pm UTC](https://discourse.julialang.org/t/how-to-train-predict-a-very-simple-feed-forward-neural-network-in-flux/39534 "2021-05-26T20:42:40Z")

</div>

I must be idiot but I can’t realise how to do very basic… no Convolution, RNN, gates,… just a basic plain feed-forward neural network design/testing/validation in Flux. Somethink like: l1 = FullyConnectedLayer(tanh,2,3…

---

## [Factors for regression models in julia](https://discourse.julialang.org/t/factors-for-regression-models-in-julia/61836)

<div class="topic-metadata">

**Author:** [@Babou](https://discourse.julialang.org/u/Babou)\
**Replies:** 5\
**Last updated:** [May 26, 2021, 8:35pm UTC](https://discourse.julialang.org/t/factors-for-regression-models-in-julia/61836 "2021-05-26T20:35:50Z")

</div>

I want to build a linear mixed model in Julia but the R code I am basing it on requires the use of factors for the model. I came across a stackoverflow post on just this topic but it was from 2017 and I am hoping ther…

---

## [Is there a workaround to render symbols from Symbolics.jl in Pluto.jl](https://discourse.julialang.org/t/is-there-a-workaround-to-render-symbols-from-symbolics-jl-in-pluto-jl/61198)

<div class="topic-metadata">

**Author:** [@feanor12](https://discourse.julialang.org/u/feanor12)\
**Replies:** 4\
**Last updated:** [May 26, 2021, 8:27pm UTC](https://discourse.julialang.org/t/is-there-a-workaround-to-render-symbols-from-symbolics-jl-in-pluto-jl/61198 "2021-05-26T20:27:35Z")

</div>

When I use Symbolics.jl in Pluto.jl I get an invalid latex expression (at least for Mathjax). Is there a workaround to remove the text part from the output? I basically makes Symbolics.jl very bothersome to use. I …

---

## [Modeling Thermodynamic System in MTK](https://discourse.julialang.org/t/modeling-thermodynamic-system-in-mtk/61095)

<div class="topic-metadata">

**Author:** [@mbologna](https://discourse.julialang.org/u/mbologna)\
**Replies:** 1\
**Last updated:** [May 26, 2021, 8:21pm UTC](https://discourse.julialang.org/t/modeling-thermodynamic-system-in-mtk/61095 "2021-05-26T20:21:44Z")

</div>

I’m working on converting an existing Julia model using DifferentialEquations.jl and solving Stiff ODEs to using MTK. There seems to be some nuance to setting up ODESystems that I don’t understand. I’m modeling pressure …

---

## [How to show edges in mesh plot in Makie?](https://discourse.julialang.org/t/how-to-show-edges-in-mesh-plot-in-makie/61820)

<div class="topic-metadata">

**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 6\
**Last updated:** [May 26, 2021, 6:19pm UTC](https://discourse.julialang.org/t/how-to-show-edges-in-mesh-plot-in-makie/61820 "2021-05-26T18:19:32Z")

</div>

From the documentation, it is easy to plot a mesh given an array of coordinates and an array of connectivities: using GLMakie coords = \[ 0.0 0.0 1.0 0.0 1.0 1.0 0.0 1.0 \] connec = \[ 1 2 3 3 4 1 \] mesh(coo…

---

## [How to obtain the critical value F0 of a F-distribution?](https://discourse.julialang.org/t/how-to-obtain-the-critical-value-f0-of-a-f-distribution/36448)

<div class="topic-metadata">

**Author:** [@Fred](https://discourse.julialang.org/u/Fred)\
**Replies:** 3\
**Last updated:** [May 26, 2021, 12:16pm UTC](https://discourse.julialang.org/t/how-to-obtain-the-critical-value-f0-of-a-f-distribution/36448 "2021-05-26T12:16:50Z")

</div>

Hi, I am not statistician and I need some advises to do a statistical test in Julia. I would like to obtain the critical value F0 of a F-distribution available for example in these tables I read the Distributions.jl d…

---

## [Sensitivities with respect to initial conditions in DifferentialEquations.jl](https://discourse.julialang.org/t/sensitivities-with-respect-to-initial-conditions-in-differentialequations-jl/25555)

<div class="topic-metadata">

**Author:** [@rjpower4](https://discourse.julialang.org/u/rjpower4)\
**Replies:** 17\
**Last updated:** [May 26, 2021, 10:36am UTC](https://discourse.julialang.org/t/sensitivities-with-respect-to-initial-conditions-in-differentialequations-jl/25555 "2021-05-26T10:36:11Z")

</div>

For my research, I perform many differential corrections processes. Often times, for these processes I want the transition matrix, \\Phi(t\_1, t\_0), which is obtained by propagating the linearization of the system alongsid…

---

## [Font of annotations?](https://discourse.julialang.org/t/font-of-annotations/14998)

<div class="topic-metadata">

**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 3\
**Last updated:** [May 26, 2021, 9:24am UTC](https://discourse.julialang.org/t/font-of-annotations/14998 "2021-05-26T09:24:27Z")

</div>

dear Plots wizards—how do I set the font (size) of annotations? using Plots y= 2:20; x=2:20; f(x,y)=x+y; annotations= \[ (x\[i\],y\[j\],round(f(x\[i\],y\[j\]),digits=2)) for i=1:length(x) for j=1:length(y)\]; plot( ; annotations=…

---

## [Enumerating all possible solutions of Knapsack problem](https://discourse.julialang.org/t/enumerating-all-possible-solutions-of-knapsack-problem/61800)

<div class="topic-metadata">

**Author:** [@Tomas\_Pevny](https://discourse.julialang.org/u/Tomas_Pevny)\
**Replies:** 3\
**Last updated:** [May 26, 2021, 3:57am UTC](https://discourse.julialang.org/t/enumerating-all-possible-solutions-of-knapsack-problem/61800 "2021-05-26T03:57:36Z")

</div>

Dear All, I would like to ask, if anyone has experimented with an algorithm to enumerate all possible solutions of the knapsack problem. I have seen scientific papers solving this problem and would like to know, if some…

---

## [Help with JuMP variables](https://discourse.julialang.org/t/help-with-jump-variables/61733)

<div class="topic-metadata">

**Author:** [@Dan.phi](https://discourse.julialang.org/u/Dan.phi)\
**Replies:** 1\
**Last updated:** [May 25, 2021, 11:34pm UTC](https://discourse.julialang.org/t/help-with-jump-variables/61733 "2021-05-25T23:34:40Z")

</div>

I am trying to solve a constrained optimization problem using JuMP, but there is apparently a conflict between how I define the variables and one of the packages I call in the objective function. I just started with JuMP…

---

## [COSMO.jl & Convex.jl: setting intial values](https://discourse.julialang.org/t/cosmo-jl-convex-jl-setting-intial-values/61381)

<div class="topic-metadata">

**Author:** [@lrnv](https://discourse.julialang.org/u/lrnv)\
**Replies:** 4\
**Last updated:** [May 25, 2021, 7:49pm UTC](https://discourse.julialang.org/t/cosmo-jl-convex-jl-setting-intial-values/61381 "2021-05-25T19:49:44Z")

</div>

Hi, I’m using COSMO.jl as a solver from Convex.jl. I’m solving tseveral ‘related problems’ over and over again, which correspond to more precise versions of each others. I’d like to use the COSMO.jl warm starting featu…

---

## [KeyError: key "Xorg\_libXrender\_jll" not found](https://discourse.julialang.org/t/keyerror-key-xorg-libxrender-jll-not-found/61770)

<div class="topic-metadata">

**Author:** [@Aquaman](https://discourse.julialang.org/u/Aquaman)\
**Replies:** 0\
**Last updated:** [May 25, 2021, 10:22am UTC](https://discourse.julialang.org/t/keyerror-key-xorg-libxrender-jll-not-found/61770 "2021-05-25T10:22:24Z")

</div>

I cannot install Plots.jl in Julia 1.6.1 due to the error “KeyError: key “Xorg\_libXrender\_jll” not found”

---

## [JumpProblem with large number of jumps crashes](https://discourse.julialang.org/t/jumpproblem-with-large-number-of-jumps-crashes/61444)

<div class="topic-metadata">

**Author:** [@gzagatti](https://discourse.julialang.org/u/gzagatti)\
**Replies:** 13\
**Last updated:** [May 25, 2021, 8:00am UTC](https://discourse.julialang.org/t/jumpproblem-with-large-number-of-jumps-crashes/61444 "2021-05-25T08:00:06Z")

</div>

Hello, I am trying to solve a JumpProblem defined on a network. The problem consists of a SIR model in which I am trying to model every node of the network separately. I have a working code that works with a small net…

---

## [Trying to understand the use of shared memory on GPUs](https://discourse.julialang.org/t/trying-to-understand-the-use-of-shared-memory-on-gpus/61240)

<div class="topic-metadata">

**Author:** [@Ferran\_Mazzanti](https://discourse.julialang.org/u/Ferran_Mazzanti)\
**Replies:** 3\
**Last updated:** [May 25, 2021, 5:47am UTC](https://discourse.julialang.org/t/trying-to-understand-the-use-of-shared-memory-on-gpus/61240 "2021-05-25T05:47:38Z")

</div>

Hi, I’m trying to learn how to use shared memory on the GPU by following the very nice write-up in https://jenni-westoby.github.io/Julia\_GPU\_examples/dev/Vector\_dot\_product/ however, I fail to understand basic things …

---

## [Cxx.jl Compatability with Julia 1.5+](https://discourse.julialang.org/t/cxx-jl-compatability-with-julia-1-5/53782)

<div class="topic-metadata">

**Author:** [@cadojo](https://discourse.julialang.org/u/cadojo)\
**Replies:** 7\
**Last updated:** [May 25, 2021, 4:57am UTC](https://discourse.julialang.org/t/cxx-jl-compatability-with-julia-1-5/53782 "2021-05-25T04:57:52Z")

</div>

The package Cxx.jl seems to be partially compatible with Julia 1.3, and not compatible with Julia 1.5+ (as referenced by this discourse post and #464). Does Julia 1.5 introduce permanent incompatibilities with a project…

---

## [JSON3.jl parse custom type with NaN](https://discourse.julialang.org/t/json3-jl-parse-custom-type-with-nan/61295)

<div class="topic-metadata">

**Author:** [@ohmsweetohm1](https://discourse.julialang.org/u/ohmsweetohm1)\
**Replies:** 3\
**Last updated:** [May 25, 2021, 3:45am UTC](https://discourse.julialang.org/t/json3-jl-parse-custom-type-with-nan/61295 "2021-05-25T03:45:49Z")

</div>

The following works: struct Foo a::Vector{Float64} b::Float64 end JSON3.StructType(::Type{Foo}) = JSON3.Struct() str = JSON3.write(Foo(\[NaN, 2.3\], NaN), allow\_inf=true) JSON3.read(str, Foo, allow\_inf=true) Wi…

---

## [Fatal error while reading in messy data using DataFrames, CSV](https://discourse.julialang.org/t/fatal-error-while-reading-in-messy-data-using-dataframes-csv/61314)

<div class="topic-metadata">

**Author:** [@jessecm](https://discourse.julialang.org/u/jessecm)\
**Replies:** 6\
**Last updated:** [May 25, 2021, 3:28am UTC](https://discourse.julialang.org/t/fatal-error-while-reading-in-messy-data-using-dataframes-csv/61314 "2021-05-25T03:28:22Z")

</div>

Hi, while reading in a large, messy dataset, I got the message: using DataFrames, CSV, Random, Tables GBIF\_chordate = CSV.read("occurrence.txt", DataFrame; header = true); \*\*ERROR:\*\* thread = 1 fatal error, encountered …

---

## [Reshaping ID and STatus by CATegory](https://discourse.julialang.org/t/reshaping-id-and-status-by-category/61716)

<div class="topic-metadata">

**Author:** [@rocco\_sprmnt21](https://discourse.julialang.org/u/rocco_sprmnt21)\
**Replies:** 2\
**Last updated:** [May 24, 2021, 7:55pm UTC](https://discourse.julialang.org/t/reshaping-id-and-status-by-category/61716 "2021-05-24T19:55:42Z")

</div>

I would like to see (some of) the different ways in which we can transform the following dataframe df=DataFrame(CAT=\["A","B","C","A","B","C","D","E","A","C","D"\], ID=\[1,1,1,2,2,2,2,2,3,3,3\], ST=\["q","q"…

---

## [Reading Multiple Files in a Folder Into a tensor in Julia](https://discourse.julialang.org/t/reading-multiple-files-in-a-folder-into-a-tensor-in-julia/61324)

<div class="topic-metadata">

**Author:** [@phantom](https://discourse.julialang.org/u/phantom)\
**Replies:** 8\
**Last updated:** [May 24, 2021, 7:43pm UTC](https://discourse.julialang.org/t/reading-multiple-files-in-a-folder-into-a-tensor-in-julia/61324 "2021-05-24T19:43:04Z")

</div>

New to Julia and programming in general so this is a two part question. Suppose I have a Folder with 3,000 CSV files. Each file is roughly 7,000 x 7. (The number of rows may vary from file to file but the number of co…

---

## [How to implement a real time DAE solver](https://discourse.julialang.org/t/how-to-implement-a-real-time-dae-solver/61719)

<div class="topic-metadata">

**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 12\
**Last updated:** [May 24, 2021, 4:13pm UTC](https://discourse.julialang.org/t/how-to-implement-a-real-time-dae-solver/61719 "2021-05-24T16:13:27Z")

</div>

I have the following solver: differential\_vars = ones(Bool, 36) prob = DAEProblem(residual!, yd0, y0, tspan, differential\_vars=differential\_vars) solver = IDA(linear\_solver=:Dense) @time sol = solve(prob, solver, save…

---

## [Plotting a closed curve in 3D](https://discourse.julialang.org/t/plotting-a-closed-curve-in-3d/61691)

<div class="topic-metadata">

**Author:** [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Replies:** 4\
**Last updated:** [May 24, 2021, 2:23pm UTC](https://discourse.julialang.org/t/plotting-a-closed-curve-in-3d/61691 "2021-05-24T14:23:06Z")

</div>

How do you plot a closed curve in Julia? For instance using Plots.jl. I would like to draw an ellipse into a 3-dimensional plot.

---

## [Macro capturing intermediate values](https://discourse.julialang.org/t/macro-capturing-intermediate-values/61715)

<div class="topic-metadata">

**Author:** [@MeinAccount](https://discourse.julialang.org/u/MeinAccount)\
**Replies:** 0\
**Last updated:** [May 24, 2021, 10:15am UTC](https://discourse.julialang.org/t/macro-capturing-intermediate-values/61715 "2021-05-24T10:15:30Z")

</div>

I just wanted to show of a fun little macro I wrote. Doing a course on stochastic simulation, I’m writing small functions that simulate some process. For performance reasons I don’t want to emit all the intermediate valu…

---

## [Transforming dataframe columns selected via regex while keeping the other columns](https://discourse.julialang.org/t/transforming-dataframe-columns-selected-via-regex-while-keeping-the-other-columns/61702)

<div class="topic-metadata">

**Author:** [@anon71627001](https://discourse.julialang.org/u/anon71627001)\
**Replies:** 4\
**Last updated:** [May 24, 2021, 10:03am UTC](https://discourse.julialang.org/t/transforming-dataframe-columns-selected-via-regex-while-keeping-the-other-columns/61702 "2021-05-24T10:03:40Z")

</div>

Let’s say I have df = DataFrame(ax = 1:3, bx = 4:6, cy = 7:9, dy = 10:12) and want to double the values of each column that has an “x” in its header, while leaving the columns that don’t have an “x” in their header uncha…

---

## [SDDiP: Could not solve for Lagrangian duals. Iteration limit exceeded](https://discourse.julialang.org/t/sddip-could-not-solve-for-lagrangian-duals-iteration-limit-exceeded/61673)

<div class="topic-metadata">

**Author:** [@BYS](https://discourse.julialang.org/u/BYS)\
**Replies:** 5\
**Last updated:** [May 24, 2021, 8:44am UTC](https://discourse.julialang.org/t/sddip-could-not-solve-for-lagrangian-duals-iteration-limit-exceeded/61673 "2021-05-24T08:44:09Z")

</div>

I have tried a SDDP model including integer using “integrality\_handler=SDDP.SDDiP()”, and I set SDDP.train(model; iteration\_limit = 10) The results are as follows, ERROR: LoadError: Could not solve for Lagrangian dual…

---

## [Save multiple plots on separate pages of one PDF](https://discourse.julialang.org/t/save-multiple-plots-on-separate-pages-of-one-pdf/41953)

<div class="topic-metadata">

**Author:** [@corbat](https://discourse.julialang.org/u/corbat)\
**Replies:** 3\
**Last updated:** [May 24, 2021, 5:42am UTC](https://discourse.julialang.org/t/save-multiple-plots-on-separate-pages-of-one-pdf/41953 "2021-05-24T05:42:26Z")

</div>

Hi, is there a way to save multiple plots, more precisely multiple figures generated with Plots.jl, on separate pages of a single PDF file?

---

## [Optim.jl vs NLopt.jl vs?](https://discourse.julialang.org/t/optim-jl-vs-nlopt-jl-vs/61692)

<div class="topic-metadata">

**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 8\
**Last updated:** [May 24, 2021, 4:00am UTC](https://discourse.julialang.org/t/optim-jl-vs-nlopt-jl-vs/61692 "2021-05-24T04:00:08Z")

</div>

I have a kind of hard nonlinear optimization problem. 12 variables, I know the result of the function should be zero, but how to find the combination of 12 values that give a very low residual? So far I tried Optim.jl a…

---

## [Makie - High GPU usage for plots with a lot of points](https://discourse.julialang.org/t/makie-high-gpu-usage-for-plots-with-a-lot-of-points/55199)

<div class="topic-metadata">

**Author:** [@tt1234567](https://discourse.julialang.org/u/tt1234567)\
**Replies:** 15\
**Last updated:** [May 23, 2021, 6:59pm UTC](https://discourse.julialang.org/t/makie-high-gpu-usage-for-plots-with-a-lot-of-points/55199 "2021-05-23T18:59:29Z")

</div>

My laptop struggles a bit when I plot large numbers of points with Makie. It’s not just while it’s plotting but it carries on using the GPU after the plot’s completed. I’m using Windows 10 on a laptop with a core i7 proc…

---

## [How to layout figures in CairoMakie after they are generated](https://discourse.julialang.org/t/how-to-layout-figures-in-cairomakie-after-they-are-generated/61683)

<div class="topic-metadata">

**Author:** [@vjd](https://discourse.julialang.org/u/vjd)\
**Replies:** 2\
**Last updated:** [May 23, 2021, 4:20pm UTC](https://discourse.julialang.org/t/how-to-layout-figures-in-cairomakie-after-they-are-generated/61683 "2021-05-23T16:20:53Z")

</div>

Note: Question on slack that I reposting here for wider audience. Is there a way to layout figures in CairoMakie after they are generated? e.g. I have julia\> typeof(a1) Figure julia\> typeof(a2) Figure I want to snap …

---

## [How to solve Ax=b, with A,x,b are matrix](https://discourse.julialang.org/t/how-to-solve-ax-b-with-a-x-b-are-matrix/61663)

<div class="topic-metadata">

**Author:** [@Van\_Kh\_i\_Ph\_m](https://discourse.julialang.org/u/Van_Kh_i_Ph_m)\
**Replies:** 12\
**Last updated:** [May 23, 2021, 4:16pm UTC](https://discourse.julialang.org/t/how-to-solve-ax-b-with-a-x-b-are-matrix/61663 "2021-05-23T16:16:10Z")

</div>

How to solve Ax=b, with A,x,b are matrix And, Can anyone help me solve this function with Newton method with backtracking line search ?

---

## [JuliaCon2020 Dynamical Modelling BoF summary](https://discourse.julialang.org/t/juliacon2020-dynamical-modelling-bof-summary/44099)

<div class="topic-metadata">

**Author:** [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Replies:** 5\
**Last updated:** [January 26, 2021, 9:14am UTC](https://discourse.julialang.org/t/juliacon2020-dynamical-modelling-bof-summary/44099 "2021-01-26T09:14:34Z")

</div>

Hi everyone, below you will find the summary of the BoF session of JuliaCon2020. I’ve tried to make everything sensible, feel free to correct me in the comments! Our working definition of “dynamical modelling” is: Mod…

[Previous page](https://discourse.julialang.org/c/domain/10.md?page=362)

[Next page](https://discourse.julialang.org/c/domain/10.md?page=364)