# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=423

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**Page:** 424

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## [How to treat variable as binary in some points of model?](https://discourse.julialang.org/t/how-to-treat-variable-as-binary-in-some-points-of-model/46100)

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**Author:** [@sogrbilja](https://discourse.julialang.org/u/sogrbilja)\
**Replies:** 3\
**Last updated:** [September 5, 2020, 2:50pm UTC](https://discourse.julialang.org/t/how-to-treat-variable-as-binary-in-some-points-of-model/46100 "2020-09-05T14:50:16Z")

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I have a decision variable PRODAMOUNT and it is of Int type. I need it as binary in some points of the model, like here in the objective function second PRODAMOUNT should be used as 1 when there is a positive value in it…

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## [Error: Problems with using VectorOfArray() with DifferentialEquations package](https://discourse.julialang.org/t/error-problems-with-using-vectorofarray-with-differentialequations-package/46049)

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**Author:** [@MJMAG](https://discourse.julialang.org/u/MJMAG)\
**Replies:** 4\
**Last updated:** [September 5, 2020, 11:13am UTC](https://discourse.julialang.org/t/error-problems-with-using-vectorofarray-with-differentialequations-package/46049 "2020-09-05T11:13:32Z")

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Hey there, I am new to the community. I don’t have too much experience with the DifferentialEquations package. I am trying to model Lotka Volterra dynamics with two guilds and in these guilds various species. For this…

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## [Custom node dependent \`nodesize\`](https://discourse.julialang.org/t/custom-node-dependent-nodesize/46098)

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**Author:** [@ohmsweetohm1](https://discourse.julialang.org/u/ohmsweetohm1)\
**Replies:** 0\
**Last updated:** [September 5, 2020, 11:09am UTC](https://discourse.julialang.org/t/custom-node-dependent-nodesize/46098 "2020-09-05T11:09:13Z")

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Is it possible to use a custom method to compute the node size for a tree? using AbstractTrees, Plots, GraphRecipes mutable struct BinaryNode{T} data::T parent::BinaryNode{T} left::BinaryNode{T} right::…

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## [Shared base library for PPL](https://discourse.julialang.org/t/shared-base-library-for-ppl/45901)

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**Author:** [@cscherrer](https://discourse.julialang.org/u/cscherrer)\
**Replies:** 9\
**Last updated:** [September 5, 2020, 8:29am UTC](https://discourse.julialang.org/t/shared-base-library-for-ppl/45901 "2020-09-05T08:29:40Z")

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Hong Ge (are you on Disourse?) recently posted this comment in the probprog channel on Slack: …I think it is quite helpful to consider carefully how we, as a community, can work together to build a better platform for …

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## [Stipple.jl Issues on Heroku](https://discourse.julialang.org/t/stipple-jl-issues-on-heroku/46086)

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**Author:** [@nucklass](https://discourse.julialang.org/u/nucklass)\
**Replies:** 0\
**Last updated:** [September 5, 2020, 3:10am UTC](https://discourse.julialang.org/t/stipple-jl-issues-on-heroku/46086 "2020-09-05T03:10:59Z")

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Hi all, I’ve been trying out stipple the last few days as an alternative to RShiny and Tableau. I’ve been able to get a nice little dashboard and I wanted to post it online to share with a few other students. By followi…

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## [Apache Arrow 1.0 release](https://discourse.julialang.org/t/apache-arrow-1-0-release/43786)

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**Author:** [@dmbates](https://discourse.julialang.org/u/dmbates)\
**Replies:** 7\
**Last updated:** [September 5, 2020, 1:28am UTC](https://discourse.julialang.org/t/apache-arrow-1-0-release/43786 "2020-09-05T01:28:45Z")

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Version 1.0.0 of the Apache Arrow specification and implementations in several languages has been released Apache Arrow 1.0.0 Release | Apache Arrow As part of this release the Feather file specification (a file format …

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## [Regression Random Forests: Mean coeff of determination in cross-validation surprisingly too good for pure noise inputs](https://discourse.julialang.org/t/regression-random-forests-mean-coeff-of-determination-in-cross-validation-surprisingly-too-good-for-pure-noise-inputs/46073)

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**Author:** [@rio](https://discourse.julialang.org/u/rio)\
**Replies:** 1\
**Last updated:** [September 4, 2020, 11:26pm UTC](https://discourse.julialang.org/t/regression-random-forests-mean-coeff-of-determination-in-cross-validation-surprisingly-too-good-for-pure-noise-inputs/46073 "2020-09-04T23:26:46Z")

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I fitted a regression RF model on random (low dimensional) noise data and got surprising good estimates of the Mean Coeff of Determination using Cross-Validation. Here is my code, based on the example in https://github.…

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## [Recording entry and exit time of state space sets with DifferentialEquations.jl](https://discourse.julialang.org/t/recording-entry-and-exit-time-of-state-space-sets-with-differentialequations-jl/46029)

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**Author:** [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Replies:** 14\
**Last updated:** [September 4, 2020, 11:05pm UTC](https://discourse.julialang.org/t/recording-entry-and-exit-time-of-state-space-sets-with-differentialequations-jl/46029 "2020-09-04T23:05:55Z")

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I am trying to estimate entry and exit times in sets of the state space, as functionality for DynamicalSystems.jl. I have a working implementation for discrete systems but for continuous it turns out it is much harder. O…

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## [How to write device code?](https://discourse.julialang.org/t/how-to-write-device-code/11527)

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**Author:** [@floswald](https://discourse.julialang.org/u/floswald)\
**Replies:** 4\
**Last updated:** [September 4, 2020, 10:32pm UTC](https://discourse.julialang.org/t/how-to-write-device-code/11527 "2020-09-04T22:32:48Z")

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hi there newcomer question here. suppose i am looking at some cuda code that has a function like \_\_device\_\_ int binaryVal(const REAL x, const int n, const REAL\* X) { } where I read the \_\_device\_\_ thing as saying that …

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## [Tennis Lineup Optimizer](https://discourse.julialang.org/t/tennis-lineup-optimizer/46036)

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**Author:** [@Cameron\_Taylor](https://discourse.julialang.org/u/Cameron_Taylor)\
**Replies:** 2\
**Last updated:** [September 4, 2020, 4:03pm UTC](https://discourse.julialang.org/t/tennis-lineup-optimizer/46036 "2020-09-04T16:03:31Z")

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Hi all, I’m putting together a little tennis lineup optimizer program to play some daily fantasy contests during the US Open here. I’m trying to write a constraint that picks a set of players on the condition that a pl…

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## [Changing size of ODE system: resize! works but deleteat! doesn't](https://discourse.julialang.org/t/changing-size-of-ode-system-resize-works-but-deleteat-doesnt/45900)

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**Author:** [@levasco](https://discourse.julialang.org/u/levasco)\
**Replies:** 5\
**Last updated:** [September 4, 2020, 3:54pm UTC](https://discourse.julialang.org/t/changing-size-of-ode-system-resize-works-but-deleteat-doesnt/45900 "2020-09-04T15:54:51Z")

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I am playing around with the capacity of changing the size of an ODE system by tweaking the example presented here. For some reason, shrinking the model by resize!()ing the integrator works as expected, but the (equivale…

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## [Find dependent variables as GenericAffExpr](https://discourse.julialang.org/t/find-dependent-variables-as-genericaffexpr/46009)

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**Author:** [@umbe](https://discourse.julialang.org/u/umbe)\
**Replies:** 4\
**Last updated:** [September 4, 2020, 7:56am UTC](https://discourse.julialang.org/t/find-dependent-variables-as-genericaffexpr/46009 "2020-09-04T07:56:27Z")

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Hi everybody! I’m trying to find a way to obtain the dependent variables of a nonlinear system as GenericAffExpr, expressed as a function only of the independent variables of an optimization problem. To be more precise…

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## [Error evaluating sparse, analytical Jacobian from ModelingToolkit in DAE system](https://discourse.julialang.org/t/error-evaluating-sparse-analytical-jacobian-from-modelingtoolkit-in-dae-system/45764)

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**Author:** [@DAEhelp](https://discourse.julialang.org/u/DAEhelp)\
**Replies:** 4\
**Last updated:** [September 4, 2020, 1:30am UTC](https://discourse.julialang.org/t/error-evaluating-sparse-analytical-jacobian-from-modelingtoolkit-in-dae-system/45764 "2020-09-04T01:30:25Z")

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I am having trouble with taking a sparse, analytical Jacobian generated in ModelingToolkit and passing it to my Sundials IDA solver. Here is an MWE adapted from a previous question. Running this segment of code with a p…

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## [Using JuMPeR](https://discourse.julialang.org/t/using-jumper/46000)

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**Author:** [@RaquelSantos](https://discourse.julialang.org/u/RaquelSantos)\
**Replies:** 1\
**Last updated:** [September 3, 2020, 8:58pm UTC](https://discourse.julialang.org/t/using-jumper/46000 "2020-09-03T20:58:19Z")

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I look for articles that talk about robust optimization using JuMPeR. Can someone refer me? Thank you!

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## [ODE AutoTsit5(Rodas5()) switching bug (depends from tolerance history)](https://discourse.julialang.org/t/ode-autotsit5-rodas5-switching-bug-depends-from-tolerance-history/45288)

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**Author:** [@peatlux](https://discourse.julialang.org/u/peatlux)\
**Replies:** 8\
**Last updated:** [September 3, 2020, 7:42pm UTC](https://discourse.julialang.org/t/ode-autotsit5-rodas5-switching-bug-depends-from-tolerance-history/45288 "2020-09-03T19:42:00Z")

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I want to solve my coupled DiffEq with different algorithms, because i don’t know the specific characteristics of it. But i know that it can exhibit stiff behaviour in some cases. I need to solve it many times in a param…

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## [Providing More Initial Parameter Values than there are Parameters in the Function Being Optimized](https://discourse.julialang.org/t/providing-more-initial-parameter-values-than-there-are-parameters-in-the-function-being-optimized/45585)

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**Author:** [@donkeysaddle](https://discourse.julialang.org/u/donkeysaddle)\
**Replies:** 9\
**Last updated:** [September 3, 2020, 5:51pm UTC](https://discourse.julialang.org/t/providing-more-initial-parameter-values-than-there-are-parameters-in-the-function-being-optimized/45585 "2020-09-03T17:51:45Z")

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Why does the “extra” parameter value affect the optimization? Apologies if this is in the Optim documentation - I didn’t see it. For example: using Optim f(x) = (1.0 - x\[1\])^2 + 100.0 \* (x\[2\] - x\[1\]^2)^2 x0 = \[0.0, 0.…

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## [How to deal with multiple processes trying to load the same file (and crash)?](https://discourse.julialang.org/t/how-to-deal-with-multiple-processes-trying-to-load-the-same-file-and-crash/46005)

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**Author:** [@volkerkarle](https://discourse.julialang.org/u/volkerkarle)\
**Replies:** 3\
**Last updated:** [September 3, 2020, 2:52pm UTC](https://discourse.julialang.org/t/how-to-deal-with-multiple-processes-trying-to-load-the-same-file-and-crash/46005 "2020-09-03T14:52:14Z")

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hey folks, Right now I have the issue that multiple jobs on a cluster try to load the same data (my data is saved using JLD) and there is a problem with the disk, as a result the jobs fail. How can I deal with this issu…

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## [Zygote + CUDA: scalar getindex with custom activation function using multiplication](https://discourse.julialang.org/t/zygote-cuda-scalar-getindex-with-custom-activation-function-using-multiplication/45997)

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**Author:** [@HenriDeh](https://discourse.julialang.org/u/HenriDeh)\
**Replies:** 3\
**Last updated:** [September 3, 2020, 1:40pm UTC](https://discourse.julialang.org/t/zygote-cuda-scalar-getindex-with-custom-activation-function-using-multiplication/45997 "2020-09-03T13:40:35Z")

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This simple model training does not work because of the custom activation function: julia\> using CUDA,Flux julia\> CUDA.allowscalar(false) julia\> const c = 100 100 julia\> f(x) = σ(x)\*2\*c f (generic function with 1 met…

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## [Using LSTM with Conv layers](https://discourse.julialang.org/t/using-lstm-with-conv-layers/46007)

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**Author:** [@nantonel](https://discourse.julialang.org/u/nantonel)\
**Replies:** 0\
**Last updated:** [September 3, 2020, 1:32pm UTC](https://discourse.julialang.org/t/using-lstm-with-conv-layers/46007 "2020-09-03T13:32:16Z")

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I was wondering what is the best practice to use a LSTM (or any RNN) together with some convolutional layers using Flux and in general how to unite recurrent networks with other blocks. Say I have this simple problem wh…

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## [Obtain frequency response from digital filter with DSP.jl](https://discourse.julialang.org/t/obtain-frequency-response-from-digital-filter-with-dsp-jl/44618)

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**Author:** [@marcpabst](https://discourse.julialang.org/u/marcpabst)\
**Replies:** 4\
**Last updated:** [September 2, 2020, 4:59am UTC](https://discourse.julialang.org/t/obtain-frequency-response-from-digital-filter-with-dsp-jl/44618 "2020-09-02T04:59:33Z")

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Hi, I have a simple and potentially very stupid question. I use DSP.jl to construct a filter via digitalfilter(), which leaves me with a filter kernel I can apply to my signal. If I wanted to take a look at the respons…

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## [Need help with building constraints](https://discourse.julialang.org/t/need-help-with-building-constraints/45911)

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**Author:** [@sogrbilja](https://discourse.julialang.org/u/sogrbilja)\
**Replies:** 9\
**Last updated:** [September 2, 2020, 8:20pm UTC](https://discourse.julialang.org/t/need-help-with-building-constraints/45911 "2020-09-02T20:20:34Z")

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I am trying to fit images to A4 piece of paper, I am getting infeasible solution but I don’t understand why. params = Dict() params\["ROWS"\] = 1:297 params\["COLS"\] = 1:210 params\["TOTAL"\] = 210 \* 297 params\["I…

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## [Empty list in sum create an error](https://discourse.julialang.org/t/empty-list-in-sum-create-an-error/45962)

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**Author:** [@cotepascal76](https://discourse.julialang.org/u/cotepascal76)\
**Replies:** 6\
**Last updated:** [September 2, 2020, 7:14pm UTC](https://discourse.julialang.org/t/empty-list-in-sum-create-an-error/45962 "2020-09-02T19:14:31Z")

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I would to define a constraint in jump using this compact notation like: sum( sum( Flow\[p,j\] for j in A\[p\] if j == "TT" ) for p in pars) ) the problem is that for a given p, there may be no “TT” in A\[p\] list and in …

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## [\[ANN\] GMAT.jl: Run NASA's General Mission Analysis Tool from Julia](https://discourse.julialang.org/t/ann-gmat-jl-run-nasas-general-mission-analysis-tool-from-julia/45959)

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**Author:** [@helgee](https://discourse.julialang.org/u/helgee)\
**Replies:** 2\
**Last updated:** [September 2, 2020, 4:54pm UTC](https://discourse.julialang.org/t/ann-gmat-jl-run-nasas-general-mission-analysis-tool-from-julia/45959 "2020-09-02T16:54:53Z")

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Hi folks, I want to announce another small but exciting package: https://github.com/JuliaSpace/GMAT.jl This package allows you to run scripts written for NASA’s General Mission Analysis Tool from the convenience of yo…

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## [More accurate evalpoly](https://discourse.julialang.org/t/more-accurate-evalpoly/45932)

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**Author:** [@Oscar\_Smith](https://discourse.julialang.org/u/Oscar_Smith)\
**Replies:** 8\
**Last updated:** [September 2, 2020, 4:24pm UTC](https://discourse.julialang.org/t/more-accurate-evalpoly/45932 "2020-09-02T16:24:21Z")

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In my quest for a better exp function, I discovered that having a more accurate evalpoly function is necessary if you want low error. Our builtin version is very fast (1 flop per degree), but has an unfortunately high ma…

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## [SymPy vs Sympy.jl and/or symengine.jl](https://discourse.julialang.org/t/sympy-vs-sympy-jl-and-or-symengine-jl/39464)

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**Author:** [@SanAlphaTau](https://discourse.julialang.org/u/SanAlphaTau)\
**Replies:** 14\
**Last updated:** [September 2, 2020, 12:13pm UTC](https://discourse.julialang.org/t/sympy-vs-sympy-jl-and-or-symengine-jl/39464 "2020-09-02T12:13:15Z")

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Hello, I’ve been using python and sympy to build up a series of quite large symbolic equations. I then use python to evaluate them numerically and solve for minima (using a combination of lambdify and scipy optimize). T…

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## [How to make a Custom Layer work on GPU?](https://discourse.julialang.org/t/how-to-make-a-custom-layer-work-on-gpu/45836)

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**Author:** [@pineapplehunter](https://discourse.julialang.org/u/pineapplehunter)\
**Replies:** 3\
**Last updated:** [September 2, 2020, 11:57am UTC](https://discourse.julialang.org/t/how-to-make-a-custom-layer-work-on-gpu/45836 "2020-09-02T11:57:02Z")

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Hi. I’m trying to implement a funnel activation(FReLU) like this github for fun. https://github.com/megvii-model/FunnelAct An Pytorch implementation looks like this. import torch import torch.nn as nn class FReLU(nn.M…

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## [Understanding LightGraph's depth-first search](https://discourse.julialang.org/t/understanding-lightgraphs-depth-first-search/45785)

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**Author:** [@mroavi](https://discourse.julialang.org/u/mroavi)\
**Replies:** 2\
**Last updated:** [September 2, 2020, 11:39am UTC](https://discourse.julialang.org/t/understanding-lightgraphs-depth-first-search/45785 "2020-09-02T11:39:33Z")

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Hello everyone, I want to use the depth-first search functionality offered by LightGraphs.jl. However, I don’t seem to understand the results given by the dfs\_parents function. I wrote a simple example using LightGrap…

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## [A package for Inter-rater Reliability measures](https://discourse.julialang.org/t/a-package-for-inter-rater-reliability-measures/45938)

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**Author:** [@FPGro](https://discourse.julialang.org/u/FPGro)\
**Replies:** 0\
**Last updated:** [September 2, 2020, 9:30am UTC](https://discourse.julialang.org/t/a-package-for-inter-rater-reliability-measures/45938 "2020-09-02T09:30:29Z")

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Hello folks, Remotely related to something I work on, I stumbled about inter-rater relibility measures (see Wikipedia for example) and since I couldn’t find any existing implementations I decided to try implementing one…

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## [Linear Complementarity Problem. Non-obsolete package?](https://discourse.julialang.org/t/linear-complementarity-problem-non-obsolete-package/39665)

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**Author:** [@juliauser](https://discourse.julialang.org/u/juliauser)\
**Replies:** 14\
**Last updated:** [September 1, 2020, 12:33pm UTC](https://discourse.julialang.org/t/linear-complementarity-problem-non-obsolete-package/39665 "2020-09-01T12:33:19Z")

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I was wondering which is a fast and easy to use package for a LCP problem. The examples using Complementarity I found give me errors (things like curly brackets were used) and PATHSolver requires a license (I cannot get …

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## [Available Tables.jl implementations](https://discourse.julialang.org/t/available-tables-jl-implementations/45853)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 6\
**Last updated:** [September 1, 2020, 11:11am UTC](https://discourse.julialang.org/t/available-tables-jl-implementations/45853 "2020-09-01T11:11:01Z")

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Do we have a list of all implementations of Tables.jl in the ecosystem? The README file in Tables.jl points to integrations, but those are not necessarily table types. Do you know any other implementation besides the fo…

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