# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=425

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

**Page:** 426

---

## [Using ModelingToolkit to invert a symbolic matrix](https://discourse.julialang.org/t/using-modelingtoolkit-to-invert-a-symbolic-matrix/45642)

<div class="topic-metadata">

**Author:** [@Bruno\_Mendes](https://discourse.julialang.org/u/Bruno_Mendes)\
**Replies:** 10\
**Last updated:** [August 31, 2020, 9:31pm UTC](https://discourse.julialang.org/t/using-modelingtoolkit-to-invert-a-symbolic-matrix/45642 "2020-08-31T21:31:14Z")

</div>

Hi. I’m trying to invert a mass matrix with the purpose of decoupling the second order derivatives of a dynamic system, using ModelingToolkit.jl. The matrix is something like this: In Julia, the elements of this matr…

---

## [Faster small CUDA memory transfers (UnifiedMem?)](https://discourse.julialang.org/t/faster-small-cuda-memory-transfers-unifiedmem/45850)

<div class="topic-metadata">

**Author:** [@Alex\_Ellison](https://discourse.julialang.org/u/Alex_Ellison)\
**Replies:** 2\
**Last updated:** [August 31, 2020, 8:14pm UTC](https://discourse.julialang.org/t/faster-small-cuda-memory-transfers-unifiedmem/45850 "2020-08-31T20:14:21Z")

</div>

Hey, I’m trying to write a program which launches many kernels, but the launches depend on results of earlier kernels. Sometimes the result means a kernel should not be launched at all. They can be distributed across ma…

---

## [Table views](https://discourse.julialang.org/t/table-views/45834)

<div class="topic-metadata">

**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 7\
**Last updated:** [August 31, 2020, 5:37pm UTC](https://discourse.julialang.org/t/table-views/45834 "2020-08-31T17:37:24Z")

</div>

There are various efforts in the tables ecosystem to create a common language for table operations: Query.jl DataKnots.jl TableOperations.jl Volcanito.jl I couldn’t find in any of these efforts an operation to select …

---

## [Make plots in separate windows](https://discourse.julialang.org/t/make-plots-in-separate-windows/45815)

<div class="topic-metadata">

**Author:** [@Sanji\_Vinsmoke](https://discourse.julialang.org/u/Sanji_Vinsmoke)\
**Replies:** 7\
**Last updated:** [August 31, 2020, 8:01am UTC](https://discourse.julialang.org/t/make-plots-in-separate-windows/45815 "2020-08-31T08:01:22Z")

</div>

I want to plot different arrays and show the plot in separate windows when I run the julia script from the REPL using the include("\<name\>.jl") I searched it on the internet and I got to know about reuse = false, but whe…

---

## [LightGraphs: get all of the the shortest paths between 2 points?](https://discourse.julialang.org/t/lightgraphs-get-all-of-the-the-shortest-paths-between-2-points/28775)

<div class="topic-metadata">

**Author:** [@wherrera](https://discourse.julialang.org/u/wherrera)\
**Replies:** 1\
**Last updated:** [August 30, 2020, 8:46pm UTC](https://discourse.julialang.org/t/lightgraphs-get-all-of-the-the-shortest-paths-between-2-points/28775 "2020-08-30T20:46:33Z")

</div>

Consider using LightGraphs g = SimpleDiGraph(7) add\_edge!(g, 1, 2) add\_edge!(g, 2, 3) add\_edge!(g, 4, 5) add\_edge!(g, 5, 3) add\_edge!(g, 1, 5) add\_edge!(g, 6, 7) add\_edge!(g, 7, 3) add\_edge!(g, 1, 7) p = dijkstra\_shor…

---

## [Error building CPLEX](https://discourse.julialang.org/t/error-building-cplex/45798)

<div class="topic-metadata">

**Author:** [@Glaucio](https://discourse.julialang.org/u/Glaucio)\
**Replies:** 1\
**Last updated:** [August 30, 2020, 8:29pm UTC](https://discourse.julialang.org/t/error-building-cplex/45798 "2020-08-30T20:29:52Z")

</div>

me ajudem

---

## [How to sample a clustered group from a DataFrame?](https://discourse.julialang.org/t/how-to-sample-a-clustered-group-from-a-dataframe/45777)

<div class="topic-metadata">

**Author:** [@Jaepil\_Lee](https://discourse.julialang.org/u/Jaepil_Lee)\
**Replies:** 2\
**Last updated:** [August 30, 2020, 3:37pm UTC](https://discourse.julialang.org/t/how-to-sample-a-clustered-group-from-a-dataframe/45777 "2020-08-30T15:37:46Z")

</div>

Hello Julia users! I have been trying to implement a Bootstrap from a panel data, stored in DataFrames. I think I got it working, but I am doing it in a super inefficient way. For example, as soon as I draw a vector of…

---

## [Plotting coefplot](https://discourse.julialang.org/t/plotting-coefplot/45779)

<div class="topic-metadata">

**Author:** [@qwerytyui1234](https://discourse.julialang.org/u/qwerytyui1234)\
**Replies:** 4\
**Last updated:** [August 30, 2020, 3:25pm UTC](https://discourse.julialang.org/t/plotting-coefplot/45779 "2020-08-30T15:25:26Z")

</div>

Hello everyone, I am trying to plot something like this (attached below), but I am not able to find how to plot this particular way. How would you plot something like this? Thanks in advance.

---

## [Approximating via step function](https://discourse.julialang.org/t/approximating-via-step-function/43577)

<div class="topic-metadata">

**Author:** [@danicaratelli](https://discourse.julialang.org/u/danicaratelli)\
**Replies:** 2\
**Last updated:** [August 30, 2020, 6:53am UTC](https://discourse.julialang.org/t/approximating-via-step-function/43577 "2020-08-30T06:53:10Z")

</div>

Hello, I was wondering whether anyone knows of a package/function that approximates a function with a step function. As an example, below in blue is the data I am trying to approximate, in red is my wanted output (a ste…

---

## [How to create a loss function with 3 inputs in Flux?](https://discourse.julialang.org/t/how-to-create-a-loss-function-with-3-inputs-in-flux/45755)

<div class="topic-metadata">

**Author:** [@DeepQ](https://discourse.julialang.org/u/DeepQ)\
**Replies:** 2\
**Last updated:** [August 30, 2020, 3:51am UTC](https://discourse.julialang.org/t/how-to-create-a-loss-function-with-3-inputs-in-flux/45755 "2020-08-30T03:51:26Z")

</div>

How could I create a loss function with 3 inputs like loss(w,x,y)? Could someone show me an example?

---

## [Recommended Saves and Loads of DataFrame : JLD, CSV, etc](https://discourse.julialang.org/t/recommended-saves-and-loads-of-dataframe-jld-csv-etc/9074)

<div class="topic-metadata">

**Author:** [@ivo\_welch](https://discourse.julialang.org/u/ivo_welch)\
**Replies:** 8\
**Last updated:** [August 30, 2020, 3:36am UTC](https://discourse.julialang.org/t/recommended-saves-and-loads-of-dataframe-jld-csv-etc/9074 "2020-08-30T03:36:22Z")

</div>

I am using 0.6.2, but am planning to move to 1.0 when available. I read in an earlier discussion (/suggested-formats-for-saving-and-serialization/3230) that JLD has not been working. I have tried to save() some datafra…

---

## [Proposal for automatic diagram creation system for Julia - Inspiration Penrose](https://discourse.julialang.org/t/proposal-for-automatic-diagram-creation-system-for-julia-inspiration-penrose/45750)

<div class="topic-metadata">

**Author:** [@bradeneliason](https://discourse.julialang.org/u/bradeneliason)\
**Replies:** 1\
**Last updated:** [August 29, 2020, 6:31pm UTC](https://discourse.julialang.org/t/proposal-for-automatic-diagram-creation-system-for-julia-inspiration-penrose/45750 "2020-08-29T18:31:59Z")

</div>

Penrose is a system under development which automatically creates math diagrams that would be suitable for a textbook directly from abstract mathematical specification. A simple example is creating Venn diagrams from set…

---

## [Working with dictionaries in @variables and @constraints](https://discourse.julialang.org/t/working-with-dictionaries-in-variables-and-constraints/45726)

<div class="topic-metadata">

**Author:** [@sogrbilja](https://discourse.julialang.org/u/sogrbilja)\
**Replies:** 2\
**Last updated:** [August 29, 2020, 2:48pm UTC](https://discourse.julialang.org/t/working-with-dictionaries-in-variables-and-constraints/45726 "2020-08-29T14:48:43Z")

</div>

I wonder if it is possible to work with Dict in @variables and @constraints like this: \_ORDER\_PRODUCTS and UNITS are Dict @constraint(premex, PRODAMOUNTint\_upper\[op in \_ORDER\_PRODUCTS, u in UNITS, t in TIME\], …

---

## [Expressions for partial derivatives using AD tools](https://discourse.julialang.org/t/expressions-for-partial-derivatives-using-ad-tools/45741)

<div class="topic-metadata">

**Author:** [@JLHTM](https://discourse.julialang.org/u/JLHTM)\
**Replies:** 2\
**Last updated:** [August 29, 2020, 1:53pm UTC](https://discourse.julialang.org/t/expressions-for-partial-derivatives-using-ad-tools/45741 "2020-08-29T13:53:51Z")

</div>

I have two bivariate functions (more generally, n n-variable functions) f\_1(x\_1,x\_2) and f\_2(x\_1,x\_2). I need to solve the following system of equations: \\frac{\\partial f\_1}{\\partial x\_1} = 0 and \\frac{\\partial f\_2}{\\par…

---

## [ERROR: MethodError: no method matching Model](https://discourse.julialang.org/t/error-methoderror-no-method-matching-model/45699)

<div class="topic-metadata">

**Author:** [@cotepascal76](https://discourse.julialang.org/u/cotepascal76)\
**Replies:** 2\
**Last updated:** [August 29, 2020, 10:34am UTC](https://discourse.julialang.org/t/error-methoderror-no-method-matching-model/45699 "2020-08-29T10:34:26Z")

</div>

Hello, I’m new in Julia and JuMP and I just tried to install and test JuMP but I got this error (with all solvers that I tested): julia\> Model(Gurobi.Optimizer) ERROR: MethodError: no method matching Model(::Type{Gurob…

---

## [Why does Zygote produce a wrong derivative?](https://discourse.julialang.org/t/why-does-zygote-produce-a-wrong-derivative/45724)

<div class="topic-metadata">

**Author:** [@joachimbrand1](https://discourse.julialang.org/u/joachimbrand1)\
**Replies:** 5\
**Last updated:** [August 29, 2020, 9:06am UTC](https://discourse.julialang.org/t/why-does-zygote-produce-a-wrong-derivative/45724 "2020-08-29T09:06:32Z")

</div>

Trying to get my head around AD in Julia and being inspired by Jarret Revels’ example of computing the Jacobian of a cumprod() function with ForwardDiff.jl, I tried to see whether I could get the same done with Zygote.…

---

## [Creating an array of equations in ModelingToolkit](https://discourse.julialang.org/t/creating-an-array-of-equations-in-modelingtoolkit/45712)

<div class="topic-metadata">

**Author:** [@zdenek\_hurak](https://discourse.julialang.org/u/zdenek_hurak)\
**Replies:** 2\
**Last updated:** [August 29, 2020, 2:53am UTC](https://discourse.julialang.org/t/creating-an-array-of-equations-in-modelingtoolkit/45712 "2020-08-29T02:53:04Z")

</div>

I am trying to model a set of differential equations in ModelingToolkit. And I want to formulate it using vector variables. Namely, I will have a variable vector z = \[z₁, z₂, z₃\] (just a minimal example): julia\> using M…

---

## [Symmetrical log plot](https://discourse.julialang.org/t/symmetrical-log-plot/45709)

<div class="topic-metadata">

**Author:** [@gideonsimpson](https://discourse.julialang.org/u/gideonsimpson)\
**Replies:** 1\
**Last updated:** [August 29, 2020, 2:22am UTC](https://discourse.julialang.org/t/symmetrical-log-plot/45709 "2020-08-29T02:22:33Z")

</div>

Is there anyway to do a symmetrical log plot (i.e., in both positive and negative directions), through Plots.jl? I know matplotlib has this functionality.

---

## [Why applying an integration algorithm to whole DAEs?](https://discourse.julialang.org/t/why-applying-an-integration-algorithm-to-whole-daes/45620)

<div class="topic-metadata">

**Author:** [@takunoda](https://discourse.julialang.org/u/takunoda)\
**Replies:** 3\
**Last updated:** [August 28, 2020, 7:04pm UTC](https://discourse.julialang.org/t/why-applying-an-integration-algorithm-to-whole-daes/45620 "2020-08-28T19:04:32Z")

</div>

Let me ask a fundamental question which may be trivial to experts in this field. Compared with solving a set of ODEs, solving a set of DAEs is much more difficult. For instance, in the case of electrical circuits, the e…

---

## [Call a PowerModels' function in Matlab](https://discourse.julialang.org/t/call-a-powermodels-function-in-matlab/45647)

<div class="topic-metadata">

**Author:** [@Rasoul](https://discourse.julialang.org/u/Rasoul)\
**Replies:** 2\
**Last updated:** [August 28, 2020, 4:37pm UTC](https://discourse.julialang.org/t/call-a-powermodels-function-in-matlab/45647 "2020-08-28T16:37:11Z")

</div>

Hi All, I want to call the bound tightening code in the PowerModels (i.e. following function) in Matlab. run\_obbt\_opf(case, upper\_bound, solver, model\_constructor= QCWRTriPowerModel) I tried to call “bound\_tightening\_…

---

## [Setting really small values in ODE to zero](https://discourse.julialang.org/t/setting-really-small-values-in-ode-to-zero/45693)

<div class="topic-metadata">

**Author:** [@levasco](https://discourse.julialang.org/u/levasco)\
**Replies:** 3\
**Last updated:** [August 28, 2020, 2:31pm UTC](https://discourse.julialang.org/t/setting-really-small-values-in-ode-to-zero/45693 "2020-08-28T14:31:03Z")

</div>

In modelling biological communities with ODEs, given that individuals are somewhat finite entities, I am trying to avoid infinitesimal densities which are mathematically correct but make no sense. More specifically, I wa…

---

## [Need someone to explain to me this](https://discourse.julialang.org/t/need-someone-to-explain-to-me-this/45645)

<div class="topic-metadata">

**Author:** [@sogrbilja](https://discourse.julialang.org/u/sogrbilja)\
**Replies:** 4\
**Last updated:** [August 28, 2020, 1:24pm UTC](https://discourse.julialang.org/t/need-someone-to-explain-to-me-this/45645 "2020-08-28T13:24:13Z")

</div>

I am very new to Julia and will learn, but I would ask you if you can help an explain this line by line to me: @constraints(model, begin # Constraint 1 - Only one value appears in each cell cell\[i in…

---

## [JuliaCon 2020 Birds of a Feather](https://discourse.julialang.org/t/juliacon-2020-birds-of-a-feather/39181)

<div class="topic-metadata">

**Author:** [@cscherrer](https://discourse.julialang.org/u/cscherrer)\
**Replies:** 24\
**Last updated:** [August 28, 2020, 12:31pm UTC](https://discourse.julialang.org/t/juliacon-2020-birds-of-a-feather/39181 "2020-08-28T12:31:48Z")

</div>

The “Probabilistic Programming in Julia” BoF proposal was accepted! Here’s the text: Julia’s PPL community is strong and growing. The various groups already have a strong professional relationship, but a BoF would help…

---

## [Always encounter this error after installing new packages on HPC?](https://discourse.julialang.org/t/always-encounter-this-error-after-installing-new-packages-on-hpc/44093)

<div class="topic-metadata">

**Author:** [@zxjroger](https://discourse.julialang.org/u/zxjroger)\
**Replies:** 2\
**Last updated:** [August 28, 2020, 11:45am UTC](https://discourse.julialang.org/t/always-encounter-this-error-after-installing-new-packages-on-hpc/44093 "2020-08-28T11:45:24Z")

</div>

Each time after I add a new Julia package on HPC, if I do not remove all the compiled packages in the folder “.julia/compiled” and then recompile, I will run into some random bugs. This is really annoying and I wonder wh…

---

## [\[ANN\] EarthOrientation.jl](https://discourse.julialang.org/t/ann-earthorientation-jl/5200)

<div class="topic-metadata">

**Author:** [@helgee](https://discourse.julialang.org/u/helgee)\
**Replies:** 8\
**Last updated:** [August 28, 2020, 6:39am UTC](https://discourse.julialang.org/t/ann-earthorientation-jl/5200 "2020-08-28T06:39:25Z")

</div>

I proudly present EarthOrientation.jl. Fetch the latest IERS tables: using EarthOrientation EarthOrientation.update() Get the current Earth orientation parameters, e.g. for polar motion: xp, yp = polarmotion(now()) #…

---

## [Common API for tabular data backends](https://discourse.julialang.org/t/common-api-for-tabular-data-backends/21546)

<div class="topic-metadata">

**Author:** [@bkamins](https://discourse.julialang.org/u/bkamins)\
**Replies:** 44\
**Last updated:** [August 28, 2020, 1:35am UTC](https://discourse.julialang.org/t/common-api-for-tabular-data-backends/21546 "2020-08-28T01:35:43Z")

</div>

Following the discussion on Slack I would like to open a topic here to discuss the possibility to provide a common API for different packages/ecosystems providing tabular data handling. The major rationale is that this …

---

## [How to combine two layers?](https://discourse.julialang.org/t/how-to-combine-two-layers/45635)

<div class="topic-metadata">

**Author:** [@natema](https://discourse.julialang.org/u/natema)\
**Replies:** 1\
**Last updated:** [August 27, 2020, 10:06pm UTC](https://discourse.julialang.org/t/how-to-combine-two-layers/45635 "2020-08-27T22:06:48Z")

</div>

Let’s say we have trained a model m1 m1 = Chain(Dense(10, 10, relu), Dense(10,2), softmax) and we have then substituted Dense(10,2) with Dense(10,4) and trained the latter layer only, getting a model m2 m2 = Chain(Den…

---

## [Banded matrix with ones in the lower triangular portion of the matrix](https://discourse.julialang.org/t/banded-matrix-with-ones-in-the-lower-triangular-portion-of-the-matrix/45591)

<div class="topic-metadata">

**Author:** [@joeynelson](https://discourse.julialang.org/u/joeynelson)\
**Replies:** 1\
**Last updated:** [August 27, 2020, 8:02pm UTC](https://discourse.julialang.org/t/banded-matrix-with-ones-in-the-lower-triangular-portion-of-the-matrix/45591 "2020-08-27T20:02:55Z")

</div>

I’m working on monotone spline fitting using an ispline basis. The matrix formed is similar to a banded matrix, but has all ones in the lower triangle portion below the banded portion. Additionally, I’m adding a consta…

---

## [Calculating principal curvatures of point clouds](https://discourse.julialang.org/t/calculating-principal-curvatures-of-point-clouds/45621)

<div class="topic-metadata">

**Author:** [@Roy\_Toren](https://discourse.julialang.org/u/Roy_Toren)\
**Replies:** 0\
**Last updated:** [August 27, 2020, 12:24pm UTC](https://discourse.julialang.org/t/calculating-principal-curvatures-of-point-clouds/45621 "2020-08-27T12:24:33Z")

</div>

Hello everyone, I am trying to calculate the surface variance of 3D objects. I searched for implementations of such calculations in Julia but failed to find appropriate libraries. Do you know of any libraries which im…

---

## [Monochrome theme](https://discourse.julialang.org/t/monochrome-theme/45617)

<div class="topic-metadata">

**Author:** [@yordiak](https://discourse.julialang.org/u/yordiak)\
**Replies:** 5\
**Last updated:** [August 27, 2020, 12:00pm UTC](https://discourse.julialang.org/t/monochrome-theme/45617 "2020-08-27T12:00:53Z")

</div>

For publication purposes, I am interested to create a monochrome plots. In particular, how could I implement a monochrome theme in Plots (or in any other package) , similar to the Monochrome theme of Mathematica?

[Previous page](https://discourse.julialang.org/c/domain/10.md?page=424)

[Next page](https://discourse.julialang.org/c/domain/10.md?page=426)