# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=521

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**Page:** 522

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## [Vertices that direct an edge to itself, using LightGraphs.jl, DiGraph()](https://discourse.julialang.org/t/vertices-that-direct-an-edge-to-itself-using-lightgraphs-jl-digraph/16403)

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**Author:** [@liubomyrv](https://discourse.julialang.org/u/liubomyrv)\
**Replies:** 2\
**Last updated:** [October 18, 2018, 7:44am UTC](https://discourse.julialang.org/t/vertices-that-direct-an-edge-to-itself-using-lightgraphs-jl-digraph/16403 "2018-10-18T07:44:44Z")

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Hello Julia community. I am using Julia v.0.6.4 to make visualization for a structural analysis of a linear system. And for this I am using graphs from LightGraphs.jl and specifically directed graphs function DiGraph(). …

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## [Jacchia-Bowman 2008 Atmospheric model is now available in SatelliteToolbox.jl](https://discourse.julialang.org/t/jacchia-bowman-2008-atmospheric-model-is-now-available-in-satellitetoolbox-jl/16375)

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**Author:** [@Ronis\_BR](https://discourse.julialang.org/u/Ronis_BR)\
**Replies:** 3\
**Last updated:** [October 18, 2018, 2:50am UTC](https://discourse.julialang.org/t/jacchia-bowman-2008-atmospheric-model-is-now-available-in-satellitetoolbox-jl/16375 "2018-10-18T02:50:44Z")

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Hi guys! I am back! I just want to let you know that we now have a native implementation of the Jacchia-Bowman 2008 atmospheric model in SatelliteToolbox.jl. You just need to use master because I still need to implement…

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## [Is there someone working on a port of R margins?](https://discourse.julialang.org/t/is-there-someone-working-on-a-port-of-r-margins/16469)

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**Author:** [@mwsohn](https://discourse.julialang.org/u/mwsohn)\
**Replies:** 0\
**Last updated:** [October 17, 2018, 10:50pm UTC](https://discourse.julialang.org/t/is-there-someone-working-on-a-port-of-r-margins/16469 "2018-10-17T22:50:21Z")

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This will be a very useful package to port.

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## [Querying \`JuMP.NLPEvaluator\` for objective value and constraints with MathProgBase](https://discourse.julialang.org/t/querying-jump-nlpevaluator-for-objective-value-and-constraints-with-mathprogbase/16427)

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**Author:** [@jacob-roth](https://discourse.julialang.org/u/jacob-roth)\
**Replies:** 5\
**Last updated:** [October 17, 2018, 9:51pm UTC](https://discourse.julialang.org/t/querying-jump-nlpevaluator-for-objective-value-and-constraints-with-mathprogbase/16427 "2018-10-17T21:51:56Z")

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I have an NLP model nlp\_model, and I want to evaluate its objective function / constraints at a point x. I first create an NLPEvaluator as mpb\_model = JuMP.NLPEvaluator(nlp\_model) and then try to query it with MathProgBa…

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## [Coloring pointcloud in MeshCat](https://discourse.julialang.org/t/coloring-pointcloud-in-meshcat/16465)

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**Author:** [@cserteGT3](https://discourse.julialang.org/u/cserteGT3)\
**Replies:** 0\
**Last updated:** [October 17, 2018, 7:54pm UTC](https://discourse.julialang.org/t/coloring-pointcloud-in-meshcat/16465 "2018-10-17T19:54:17Z")

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I’m experimenting with MeshCat for my project involving pointclouds and meshes. I wanted to place several pointclouds in the visualizer with different colors. I loaded them from .ply files (only vertices, without faces). …

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## [Batching issues](https://discourse.julialang.org/t/batching-issues/16444)

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**Author:** [@sdwfrost](https://discourse.julialang.org/u/sdwfrost)\
**Replies:** 1\
**Last updated:** [October 17, 2018, 6:40pm UTC](https://discourse.julialang.org/t/batching-issues/16444 "2018-10-17T18:40:49Z")

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Hi all, I’m trying to get my head around how Flux deals with batching. I can see how the mlp.jl example works in the model zoo - making one big batch using hcat, then using repeated((X,Y),200) to effectively go through …

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## [Cost for reactive power in PowerModels?](https://discourse.julialang.org/t/cost-for-reactive-power-in-powermodels/16441)

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**Author:** [@timueh](https://discourse.julialang.org/u/timueh)\
**Replies:** 1\
**Last updated:** [October 17, 2018, 3:27pm UTC](https://discourse.julialang.org/t/cost-for-reactive-power-in-powermodels/16441 "2018-10-17T15:27:38Z")

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Hi there, I am using PowerModels quite a bit – thanks @ccoffrin for this nice tool! Usually, the cost function for optimal power flow problems depends solely on the active power. For several reasons, I would like to ad…

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## [Learning Bayesian data analysis using Julia](https://discourse.julialang.org/t/learning-bayesian-data-analysis-using-julia/5370)

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**Author:** [@EricChameroy](https://discourse.julialang.org/u/EricChameroy)\
**Replies:** 22\
**Last updated:** [October 16, 2018, 1:38pm UTC](https://discourse.julialang.org/t/learning-bayesian-data-analysis-using-julia/5370 "2018-10-16T13:38:49Z")

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Hi everyone, I’m trying to teach myself Bayesian data analysis (and Julia) by working through Statistical Rethinking by Richard McElreath. Has anyone, familiar with the book, tried working through the code examples usin…

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## [Logical processes remain active after my parallelized program ends](https://discourse.julialang.org/t/logical-processes-remain-active-after-my-parallelized-program-ends/16338)

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**Author:** [@dsHitman](https://discourse.julialang.org/u/dsHitman)\
**Replies:** 4\
**Last updated:** [October 16, 2018, 10:06am UTC](https://discourse.julialang.org/t/logical-processes-remain-active-after-my-parallelized-program-ends/16338 "2018-10-16T10:06:45Z")

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Hi, I have developed a parallel version of a cellular automata but when the programm ends the logical process continue to remain active as the programm didn’t ends. Why?

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## [DataFrame group by first column, and sort by last column](https://discourse.julialang.org/t/dataframe-group-by-first-column-and-sort-by-last-column/16357)

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**Author:** [@mbeach42](https://discourse.julialang.org/u/mbeach42)\
**Replies:** 4\
**Last updated:** [October 16, 2018, 12:26am UTC](https://discourse.julialang.org/t/dataframe-group-by-first-column-and-sort-by-last-column/16357 "2018-10-16T00:26:48Z")

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Hi, Probably a simple question, but with DataFrames.jl I’m having trouble returning the data frame grouped by the first column, the sorted by the last column. Here’s a MWE using DataFrames A = rand(5,5) A\[:,1\] = \[…

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## [Fast sampling from discrete distributions](https://discourse.julialang.org/t/fast-sampling-from-discrete-distributions/16372)

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**Author:** [@vancleve](https://discourse.julialang.org/u/vancleve)\
**Replies:** 0\
**Last updated:** [October 15, 2018, 11:40pm UTC](https://discourse.julialang.org/t/fast-sampling-from-discrete-distributions/16372 "2018-10-15T23:40:45Z")

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I’m writing some population simulations that make heavy use of categorical/multinomial sampling. I can see from the code that the categorical and multinomial samplers use the alias table method. In this multinomial, the…

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## [How to pass a preconditioner to NLopt?](https://discourse.julialang.org/t/how-to-pass-a-preconditioner-to-nlopt/16361)

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**Author:** [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Replies:** 0\
**Last updated:** [October 15, 2018, 7:46pm UTC](https://discourse.julialang.org/t/how-to-pass-a-preconditioner-to-nlopt/16361 "2018-10-15T19:46:03Z")

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I found very scarce documentation about this. https://nlopt.readthedocs.io/en/stable/NLopt\_Reference/#preconditioning-with-approximate-hessians This only describes the C interface, and it seems to only support the meth…

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## [Reinforcement Learning Package](https://discourse.julialang.org/t/reinforcement-learning-package/5113)

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**Author:** [@jbrea](https://discourse.julialang.org/u/jbrea)\
**Replies:** 2\
**Last updated:** [October 15, 2018, 8:36am UTC](https://discourse.julialang.org/t/reinforcement-learning-package/5113 "2018-10-15T08:36:57Z")

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I started to write a julia package for reinforcement learning: https://jbrea.github.io/TabularReinforcementLearning.jl/latest/ Currently it contains a few algorithms for tabular environments and, on a separate branch, …

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## [JuMP.NLPEvaluator output format](https://discourse.julialang.org/t/jump-nlpevaluator-output-format/16280)

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**Author:** [@astor87](https://discourse.julialang.org/u/astor87)\
**Replies:** 1\
**Last updated:** [October 14, 2018, 4:48am UTC](https://discourse.julialang.org/t/jump-nlpevaluator-output-format/16280 "2018-10-14T04:48:23Z")

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I am trying to evaluate my constraints from my nonlinear program using IPOPT. From this discussion (https://groups.google.com/forum/#!searchin/julia-opt/evaluating$20constraints%7Csort:date/julia-opt/m1ObRwgrvGE/Mo8bjsZ1…

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## [DataFrames.jl - Vectorized row-wise function application](https://discourse.julialang.org/t/dataframes-jl-vectorized-row-wise-function-application/14513)

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**Author:** [@mdsalerno](https://discourse.julialang.org/u/mdsalerno)\
**Replies:** 3\
**Last updated:** [October 13, 2018, 10:06pm UTC](https://discourse.julialang.org/t/dataframes-jl-vectorized-row-wise-function-application/14513 "2018-10-13T22:06:22Z")

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What are efficient ways to row-wise apply a function f over a DataFrame? Looking through the DataFrames.jl documentation, I have found plenty of examples of column-wise aggregation. However, say that I want to take one…

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## [Inv() producing NaNs when called on a Tridiagonal](https://discourse.julialang.org/t/inv-producing-nans-when-called-on-a-tridiagonal/16269)

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**Author:** [@mdsalerno](https://discourse.julialang.org/u/mdsalerno)\
**Replies:** 2\
**Last updated:** [October 13, 2018, 6:53pm UTC](https://discourse.julialang.org/t/inv-producing-nans-when-called-on-a-tridiagonal/16269 "2018-10-13T18:53:20Z")

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I’m creating a 90x90 tridiagonal matrix using the function below, which I store in the variable A90. When I call inv(A90), I get a matrix of all NaNs, but if I call inv(Matrix(A90)), the inverse is successfully computed…

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## [Newbie using CSV with categorical=true](https://discourse.julialang.org/t/newbie-using-csv-with-categorical-true/16259)

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**Author:** [@ilanggear](https://discourse.julialang.org/u/ilanggear)\
**Replies:** 7\
**Last updated:** [October 13, 2018, 3:31pm UTC](https://discourse.julialang.org/t/newbie-using-csv-with-categorical-true/16259 "2018-10-13T15:31:51Z")

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How do I use the categorical=true feature of CSV.validate(…)? I’ve tried a bunch of variations, and keep getting the error “ERROR: TypeError: in setfield!, expected Union{Missing, CategoricalString{UInt32}}, got String”…

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## [Can't install any convex hull packages under 0.6.4](https://discourse.julialang.org/t/cant-install-any-convex-hull-packages-under-0-6-4/16245)

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**Author:** [@Arrigo\_Benedetti](https://discourse.julialang.org/u/Arrigo_Benedetti)\
**Replies:** 1\
**Last updated:** [October 12, 2018, 6:38pm UTC](https://discourse.julialang.org/t/cant-install-any-convex-hull-packages-under-0-6-4/16245 "2018-10-12T18:38:53Z")

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I have tried to install both ConvexHull.jl and QHull.jl for convex hull computations under Julia 0.6.4 running on Windows 10 and they both fail to install: julia\> Pkg.add("ConvexHull") ERROR: unknown package ConvexHull …

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## [Distance optimization over a matrix of observations](https://discourse.julialang.org/t/distance-optimization-over-a-matrix-of-observations/16198)

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**Author:** [@jtackm](https://discourse.julialang.org/u/jtackm)\
**Replies:** 6\
**Last updated:** [October 12, 2018, 4:21pm UTC](https://discourse.julialang.org/t/distance-optimization-over-a-matrix-of-observations/16198 "2018-10-12T16:21:04Z")

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Given a MxN matrix A with M observations and N features, as well as a non-linear distance function f, with observations being identical (f(A\[i, :\], A\[j, :\]) == 0.0 for each i,j). I would like to disturb the observations…

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## [Support for Complex-valued CuArray](https://discourse.julialang.org/t/support-for-complex-valued-cuarray/16177)

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**Author:** [@fucai](https://discourse.julialang.org/u/fucai)\
**Replies:** 2\
**Last updated:** [October 12, 2018, 1:34am UTC](https://discourse.julialang.org/t/support-for-complex-valued-cuarray/16177 "2018-10-12T01:34:33Z")

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It seems the support for complex -valued CuArray is not yet in place. Or, I may miss something here. Thanks. ‘’’ using GPUArrays, CuArrays x = randn(Float32, 3,3); x = complex(x); cx = cu(x); y = map(sin, cx) ‘’’ …

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## [Way to prevent ylabel covering yticks with pgf plots.jl?](https://discourse.julialang.org/t/way-to-prevent-ylabel-covering-yticks-with-pgf-plots-jl/16204)

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**Author:** [@djsegal](https://discourse.julialang.org/u/djsegal)\
**Replies:** 0\
**Last updated:** [October 11, 2018, 9:25pm UTC](https://discourse.julialang.org/t/way-to-prevent-ylabel-covering-yticks-with-pgf-plots-jl/16204 "2018-10-11T21:25:44Z")

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I keep running into an issue with ylabels covering yticks: What’s the easiest way to avoid this? I tried left\_margin, but that didn’t work // is there a way to just put the ylabel vertically above the top tick? (whe…

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## [The sum of an array is faster in the sequential version than in the parallelized version](https://discourse.julialang.org/t/the-sum-of-an-array-is-faster-in-the-sequential-version-than-in-the-parallelized-version/16171)

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**Author:** [@dsHitman](https://discourse.julialang.org/u/dsHitman)\
**Replies:** 9\
**Last updated:** [October 11, 2018, 3:57pm UTC](https://discourse.julialang.org/t/the-sum-of-an-array-is-faster-in-the-sequential-version-than-in-the-parallelized-version/16171 "2018-10-11T15:57:19Z")

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I have an i7 with 8 logical process but the sum of an array is faster in the sequential versione than in the parallel. Why? Am I doing something wrong? Thanks for the answers. using Distributed x = rand(1000000) #print…

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## [Writing an indicator function in JuMP](https://discourse.julialang.org/t/writing-an-indicator-function-in-jump/16145)

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**Author:** [@shoshievass](https://discourse.julialang.org/u/shoshievass)\
**Replies:** 7\
**Last updated:** [October 11, 2018, 2:46pm UTC](https://discourse.julialang.org/t/writing-an-indicator-function-in-jump/16145 "2018-10-11T14:46:39Z")

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I’d like to penalize negative values for a linear function of parameters without using an @constraint (since I’d like it to be possible, but costly to violate the constraint) Is there a way to do this within JuMP w/o de…

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## [How to use crossentropy in a multi-class classification Flux.jl neural network?](https://discourse.julialang.org/t/how-to-use-crossentropy-in-a-multi-class-classification-flux-jl-neural-network/16140)

<div class="topic-metadata">

**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 3\
**Last updated:** [October 11, 2018, 10:18am UTC](https://discourse.julialang.org/t/how-to-use-crossentropy-in-a-multi-class-classification-flux-jl-neural-network/16140 "2018-10-11T10:18:37Z")

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I am having trouble defining the crossentropy loss using Flux.jl. using Flux,StatsBase model = Flux.Chain( Dense(13\*16, 128, relu), Dense(128, 64, relu), Dense(64, 32, relu), Dense(32, 4, relu), softmax); l…

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## [Can not use CuArray on Julia 0.7](https://discourse.julialang.org/t/can-not-use-cuarray-on-julia-0-7/16089)

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**Author:** [@cuchxq](https://discourse.julialang.org/u/cuchxq)\
**Replies:** 3\
**Last updated:** [October 10, 2018, 4:19pm UTC](https://discourse.julialang.org/t/can-not-use-cuarray-on-julia-0-7/16089 "2018-10-10T16:19:14Z")

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When I use 0.7 and try to use CuArray, the following error happens: julia\> using CuArrays ┌ Warning: \`using A: B\` will only be allowed for single bindings, not modules. Use \`using A.B\` instead │ caller = ip:0x0 └ @ Co…

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## [Axis Tick Labels in Makie.jl](https://discourse.julialang.org/t/axis-tick-labels-in-makie-jl/16118)

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**Author:** [@sdmcallister](https://discourse.julialang.org/u/sdmcallister)\
**Replies:** 1\
**Last updated:** [October 10, 2018, 2:42pm UTC](https://discourse.julialang.org/t/axis-tick-labels-in-makie-jl/16118 "2018-10-10T14:42:03Z")

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Is it possible in Makie to have x-axis or y-axis tick labels that are non-numeric? I couldn’t see a way to do this in the documentation. For example, if I plot a bar chart, can the x-axis be a label like “Group 1” or “Ja…

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## [Sum of squares optimization](https://discourse.julialang.org/t/sum-of-squares-optimization/15075)

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**Author:** [@Rasoul](https://discourse.julialang.org/u/Rasoul)\
**Replies:** 5\
**Last updated:** [October 10, 2018, 12:34pm UTC](https://discourse.julialang.org/t/sum-of-squares-optimization/15075 "2018-10-10T12:34:42Z")

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I have the following optimization problem that I want to solve by the sum of squares approach. It has a linear objective function and I am looking for the best set of (a, b, and c) that satisfies a specific polynomial. m…

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## [Stepwise logistic regress - GLM - non-callable --\> callable (Non-call expression encountered)](https://discourse.julialang.org/t/stepwise-logistic-regress-glm-non-callable-callable-non-call-expression-encountered/16087)

<div class="topic-metadata">

**Author:** [@tobi](https://discourse.julialang.org/u/tobi)\
**Replies:** 7\
**Last updated:** [October 10, 2018, 12:11pm UTC](https://discourse.julialang.org/t/stepwise-logistic-regress-glm-non-callable-callable-non-call-expression-encountered/16087 "2018-10-10T12:11:18Z")

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Hello, I am trying to write a loop for a logistic regession. I have a dataframe with about 20 columns and I would like to use one of the columns after each other and print the coeftable afterwards. In the end I am aimin…

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## [Tiny fonts when using GR (Plots or not) in Jupyter](https://discourse.julialang.org/t/tiny-fonts-when-using-gr-plots-or-not-in-jupyter/16085)

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**Author:** [@Paulo\_Jabardo](https://discourse.julialang.org/u/Paulo_Jabardo)\
**Replies:** 4\
**Last updated:** [October 10, 2018, 11:17am UTC](https://discourse.julialang.org/t/tiny-fonts-when-using-gr-plots-or-not-in-jupyter/16085 "2018-10-10T11:17:25Z")

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High guys! A small glitch on GR when plotting in Jupyter is annoying me. When I plot something, the labels on the axes are very small and unreadable. This only happens on Jupyter, using GR directly or through Plots.jl. A…

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## [How to suppress printing of Flux.@epochs?](https://discourse.julialang.org/t/how-to-suppress-printing-of-flux-epochs/16063)

<div class="topic-metadata">

**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 3\
**Last updated:** [October 9, 2018, 11:36am UTC](https://discourse.julialang.org/t/how-to-suppress-printing-of-flux-epochs/16063 "2018-10-09T11:36:57Z")

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Flux.@epochs prints out lots of info. How do I suppress its input totally? Current Suppressor.jl doesn’t work on v1.0.x so can’t use that. MWE using Flux model = Flux.Chain( Dense(14\*16+4, 128, relu), Dense(128…

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