# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=456

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

**Page:** 457

---

## [Modify/reasign objective function of a model in JuMP](https://discourse.julialang.org/t/modify-reasign-objective-function-of-a-model-in-jump/36363)

<div class="topic-metadata">

**Author:** [@martincornejo](https://discourse.julialang.org/u/martincornejo)\
**Replies:** 1\
**Last updated:** [March 22, 2020, 9:19pm UTC](https://discourse.julialang.org/t/modify-reasign-objective-function-of-a-model-in-jump/36363 "2020-03-22T21:19:53Z")

</div>

I’m implementing a consensus ADMM model, and for that I wold like to iteratively solve two models, exchange information between them and solve them again with a modified objective function. The problem I’m facing right …

---

## [Franklin + API keys](https://discourse.julialang.org/t/franklin-api-keys/36321)

<div class="topic-metadata">

**Author:** [@tbeason](https://discourse.julialang.org/u/tbeason)\
**Replies:** 5\
**Last updated:** [March 22, 2020, 7:35pm UTC](https://discourse.julialang.org/t/franklin-api-keys/36321 "2020-03-22T19:35:40Z")

</div>

I am trying to build a website that just displays some sexy PlotlyJS plots using Franklin. So far, so good! But part of my code will rely on GitHub - micahjsmith/FredData.jl: Pull data from Federal Reserve Economic Data …

---

## [\[ANN\] New Version of AstroTime.jl v0.4.0](https://discourse.julialang.org/t/ann-new-version-of-astrotime-jl-v0-4-0/36340)

<div class="topic-metadata">

**Author:** [@helgee](https://discourse.julialang.org/u/helgee)\
**Replies:** 0\
**Last updated:** [March 22, 2020, 10:15am UTC](https://discourse.julialang.org/t/ann-new-version-of-astrotime-jl-v0-4-0/36340 "2020-03-22T10:15:15Z")

</div>

Hey folks, There is a new version of AstroTime.jl which is sufficiently different to warrant a new announcement here :tada: While the user-facing API has remained fairly stable, one of the most important features, tran…

---

## [JuMP Multiple Models Design Question](https://discourse.julialang.org/t/jump-multiple-models-design-question/36230)

<div class="topic-metadata">

**Author:** [@torgo](https://discourse.julialang.org/u/torgo)\
**Replies:** 5\
**Last updated:** [March 22, 2020, 12:26am UTC](https://discourse.julialang.org/t/jump-multiple-models-design-question/36230 "2020-03-22T00:26:35Z")

</div>

What is the rationale behind throwing an error in this? using JuMP m1 = Model() @variable(m1, x \>= 0) m2 = Model() @variable(m2, x \>= 0) @objective(m1, Min, x) # this will error w/ variable not owned gives ERROR: L…

---

## [Weave -- is there a way to set the margins for a pdf?](https://discourse.julialang.org/t/weave-is-there-a-way-to-set-the-margins-for-a-pdf/35345)

<div class="topic-metadata">

**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 2\
**Last updated:** [March 21, 2020, 9:37pm UTC](https://discourse.julialang.org/t/weave-is-there-a-way-to-set-the-margins-for-a-pdf/35345 "2020-03-21T21:37:54Z")

</div>

I’m able to output my data to PDF using Weave, but some of my tables are cut off and put on a row below, ruinning flow. This is understandable, but the right margin is a good 2.5" to 3" from the end of the page, where t…

---

## [How to plot very large numbers of points and save the figures with small latencies for raw audio images?](https://discourse.julialang.org/t/how-to-plot-very-large-numbers-of-points-and-save-the-figures-with-small-latencies-for-raw-audio-images/30597)

<div class="topic-metadata">

**Author:** [@mantzaris](https://discourse.julialang.org/u/mantzaris)\
**Replies:** 17\
**Last updated:** [March 21, 2020, 3:46pm UTC](https://discourse.julialang.org/t/how-to-plot-very-large-numbers-of-points-and-save-the-figures-with-small-latencies-for-raw-audio-images/30597 "2020-03-21T15:46:52Z")

</div>

I want to plot the raw signal data from audio data that is sampled at the standard 44Kbps but there is a challenge if the signal is taken for a very long time; eg. 3 hrs of signal. There is then considerable latency in t…

---

## [Convex.jl: slow in creating constraints?](https://discourse.julialang.org/t/convex-jl-slow-in-creating-constraints/34775)

<div class="topic-metadata">

**Author:** [@riccardomurri](https://discourse.julialang.org/u/riccardomurri)\
**Replies:** 34\
**Last updated:** [March 21, 2020, 11:57am UTC](https://discourse.julialang.org/t/convex-jl-slow-in-creating-constraints/34775 "2020-03-21T11:57:25Z")

</div>

Hello, I have code that builds constraints for Convex.jl in a loop; each iteration of the loop takes ~5 minutes (on fairly recent hardware). Is this expected or am I doing something wrong? # solution vector X = Variab…

---

## [Problem with cost function in JuMP](https://discourse.julialang.org/t/problem-with-cost-function-in-jump/36173)

<div class="topic-metadata">

**Author:** [@mleprovost](https://discourse.julialang.org/u/mleprovost)\
**Replies:** 3\
**Last updated:** [March 20, 2020, 9:43pm UTC](https://discourse.julialang.org/t/problem-with-cost-function-in-jump/36173 "2020-03-20T21:43:20Z")

</div>

Hello everyone, I am interested in the following optimization problem that I would like to solve with JuMP: \\begin{split} \\min\_{x \\in \\mathbb{R}^n} & (z^Tx)^2 - \\log(b^T x\[l:\\mbox{end}\])\\\\ \\mbox{ subject to }& x\[l:\\mbo…

---

## [CPLEX model answer \`has\_duals\` differently if variables were integer](https://discourse.julialang.org/t/cplex-model-answer-has-duals-differently-if-variables-were-integer/36276)

<div class="topic-metadata">

**Author:** [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Replies:** 1\
**Last updated:** [March 20, 2020, 7:10pm UTC](https://discourse.julialang.org/t/cplex-model-answer-has-duals-differently-if-variables-were-integer/36276 "2020-03-20T19:10:47Z")

</div>

Hey it is me again, XD, I would want to know if this behavior is expected (i.e., if this behavior is expected to be solver-dependent): import CPLEX, Gurobi, GLPK using JuMP function test\_duals(solver\_sym, relaxed\_mip)…

---

## [Benchmarking Optimization Heuristics](https://discourse.julialang.org/t/benchmarking-optimization-heuristics/36265)

<div class="topic-metadata">

**Author:** [@Phillip\_Sutton](https://discourse.julialang.org/u/Phillip_Sutton)\
**Replies:** 2\
**Last updated:** [March 20, 2020, 6:28pm UTC](https://discourse.julialang.org/t/benchmarking-optimization-heuristics/36265 "2020-03-20T18:28:06Z")

</div>

Does anyone have benchmarks/success stories in running Heuristics in Julia vice other Languages (Python, R, etc.)? I’m on a new team (so I don’t want to make too many bold changes) and a firm believer in Julia, looking f…

---

## [Name JuMP constraints in loop for use in writing .lp file](https://discourse.julialang.org/t/name-jump-constraints-in-loop-for-use-in-writing-lp-file/36220)

<div class="topic-metadata">

**Author:** [@ccampaigne](https://discourse.julialang.org/u/ccampaigne)\
**Replies:** 2\
**Last updated:** [March 19, 2020, 9:45pm UTC](https://discourse.julialang.org/t/name-jump-constraints-in-loop-for-use-in-writing-lp-file/36220 "2020-03-19T21:45:47Z")

</div>

Newb here (I’m a Python “user”). In JuMP 0.21.1, I want to create multiple named constraints either through vectorization or looping, and write LP files with those names so that I can easily search them for debugging pur…

---

## [Simple tool for train test split](https://discourse.julialang.org/t/simple-tool-for-train-test-split/473)

<div class="topic-metadata">

**Author:** [@klezmen](https://discourse.julialang.org/u/klezmen)\
**Replies:** 12\
**Last updated:** [March 20, 2020, 1:09am UTC](https://discourse.julialang.org/t/simple-tool-for-train-test-split/473 "2020-03-20T01:09:54Z")

</div>

Does anyone know a tool that enables me to split a dataframe in to a training set and a test set?

---

## [Error opening too many connections](https://discourse.julialang.org/t/error-opening-too-many-connections/29371)

<div class="topic-metadata">

**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 5\
**Last updated:** [March 19, 2020, 11:46pm UTC](https://discourse.julialang.org/t/error-opening-too-many-connections/29371 "2020-03-19T23:46:19Z")

</div>

I am trying to write a parallel algorithm to write to many files. Is there a way to detect how many connections I can open? Or a way to rate limit my code? ios = open.( "file".\*(1:3000), Ref("w"), ) gives error ERROR:…

---

## [Warm Starts in JuMP 0.21 & GLPK 0.12.1](https://discourse.julialang.org/t/warm-starts-in-jump-0-21-glpk-0-12-1/36223)

<div class="topic-metadata">

**Author:** [@azberman](https://discourse.julialang.org/u/azberman)\
**Replies:** 1\
**Last updated:** [March 19, 2020, 9:33pm UTC](https://discourse.julialang.org/t/warm-starts-in-jump-0-21-glpk-0-12-1/36223 "2020-03-19T21:33:17Z")

</div>

When I run a version of the code below, I receive the following error: Warning: MathOptInterface.VariablePrimalStart() is not supported by MathOptInterface.Bridges.LazyBridgeOptimizer{GLPK.Optimizer}. This information w…

---

## [Warning, invalid warm-start basis discarded](https://discourse.julialang.org/t/warning-invalid-warm-start-basis-discarded/26403)

<div class="topic-metadata">

**Author:** [@Qun](https://discourse.julialang.org/u/Qun)\
**Replies:** 18\
**Last updated:** [March 19, 2020, 8:02pm UTC](https://discourse.julialang.org/t/warning-invalid-warm-start-basis-discarded/26403 "2020-03-19T20:02:26Z")

</div>

I just learned how to use Julia 3 weeks ago. I used to use AIMMS to solve MIP problems. The considered MIP problem is about vehicle route problem. It involves over 50,000 binary variable. Without giving initial solution,…

---

## [Behaviour of sparse array variables in JuMP](https://discourse.julialang.org/t/behaviour-of-sparse-array-variables-in-jump/36185)

<div class="topic-metadata">

**Author:** [@martincornejo](https://discourse.julialang.org/u/martincornejo)\
**Replies:** 6\
**Last updated:** [March 19, 2020, 4:53pm UTC](https://discourse.julialang.org/t/behaviour-of-sparse-array-variables-in-jump/36185 "2020-03-19T16:53:17Z")

</div>

Take as an example a vector v which is of type Boolean and has n elements. Based on this vector we build a variable array x of the same length of v , but from which only the indices corresponding with the non-zero elemen…

---

## [Find simplex that contains point in triangulation](https://discourse.julialang.org/t/find-simplex-that-contains-point-in-triangulation/36181)

<div class="topic-metadata">

**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 3\
**Last updated:** [March 19, 2020, 4:43pm UTC](https://discourse.julialang.org/t/find-simplex-that-contains-point-in-triangulation/36181 "2020-03-19T16:43:58Z")

</div>

Suppose I have a triangulation on a domain in \\mathbb{R}^n, where the element simplexes are given by their vertices. What is the recommended approach for finding which simplex contains a given point? Naively, I would ju…

---

## [Define Truss Mesh in JuAFEM](https://discourse.julialang.org/t/define-truss-mesh-in-juafem/36191)

<div class="topic-metadata">

**Author:** [@FrootLoops](https://discourse.julialang.org/u/FrootLoops)\
**Replies:** 3\
**Last updated:** [March 19, 2020, 4:01pm UTC](https://discourse.julialang.org/t/define-truss-mesh-in-juafem/36191 "2020-03-19T16:01:58Z")

</div>

Hello everybody :slight\_smile: I am new to Julia and JuAFEM. Now I am trying to understand the linear Elasticity demo in juAFEM see. I understood a lot but I have big problems to adjust the code for my own purpose. I w…

---

## [Mesh/grid over convex polytope](https://discourse.julialang.org/t/mesh-grid-over-convex-polytope/36047)

<div class="topic-metadata">

**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 19\
**Last updated:** [March 19, 2020, 10:47am UTC](https://discourse.julialang.org/t/mesh-grid-over-convex-polytope/36047 "2020-03-19T10:47:31Z")

</div>

I have x\_1, \\dots, x\_m points in \\mathbb{R}^n defining a polytope as their convex hull, m \> n. Typically n = 2 or 3 and m = 4 or 5. I would like to make a more or less equispaced (adjusted when necessary) grid \\{ z\_j…

---

## [Repeatedly optimizing an LP with different data (changing coefficients/constraints)](https://discourse.julialang.org/t/repeatedly-optimizing-an-lp-with-different-data-changing-coefficients-constraints/36125)

<div class="topic-metadata">

**Author:** [@Smith](https://discourse.julialang.org/u/Smith)\
**Replies:** 7\
**Last updated:** [March 19, 2020, 8:57am UTC](https://discourse.julialang.org/t/repeatedly-optimizing-an-lp-with-different-data-changing-coefficients-constraints/36125 "2020-03-19T08:57:08Z")

</div>

Hi, I would like to solve an LP model for different sets of data and then write results to a CSV file. For illustration, assume the following code for one particular instance using JuMP using GLPK c = \[1,1\] A = \[1,1\] b …

---

## [Get on GroupedDataFrame](https://discourse.julialang.org/t/get-on-groupeddataframe/36108)

<div class="topic-metadata">

**Author:** [@Marc.Cox](https://discourse.julialang.org/u/Marc.Cox)\
**Replies:** 11\
**Last updated:** [March 18, 2020, 11:43pm UTC](https://discourse.julialang.org/t/get-on-groupeddataframe/36108 "2020-03-18T23:43:25Z")

</div>

Issue using the Base.get Get a group based on the values of the grouping columns example code here \>\> Functions · DataFrames.jl Base.get — Function. get(gd::GroupedDataFrame, key, default) Get a group based on the va…

---

## [Global sensitivity analysis - following time series](https://discourse.julialang.org/t/global-sensitivity-analysis-following-time-series/35770)

<div class="topic-metadata">

**Author:** [@alewolf](https://discourse.julialang.org/u/alewolf)\
**Replies:** 15\
**Last updated:** [March 18, 2020, 5:56pm UTC](https://discourse.julialang.org/t/global-sensitivity-analysis-following-time-series/35770 "2020-03-18T17:56:16Z")

</div>

I tested the example in https://docs.juliadiffeq.org/stable/analysis/global\_sensitivity/#GSA-examples-1. As expected it all went well. This example, calculates sensitivity with regard to the mean over time on u1 and th…

---

## [Simple example of Interactive + Dynamically Updating (VegaLite) graph with Julia backend](https://discourse.julialang.org/t/simple-example-of-interactive-dynamically-updating-vegalite-graph-with-julia-backend/36007)

<div class="topic-metadata">

**Author:** [@robertfeldt](https://discourse.julialang.org/u/robertfeldt)\
**Replies:** 5\
**Last updated:** [March 18, 2020, 3:50pm UTC](https://discourse.julialang.org/t/simple-example-of-interactive-dynamically-updating-vegalite-graph-with-julia-backend/36007 "2020-03-18T15:50:04Z")

</div>

I’m sure there are many ways this can be done in Julia but if anyone has seen very simple examples of how to produce interactive graphs that can be dynamically updated from (backend) Julia code that would be great? My s…

---

## [Problem changing Variables from Any to Real](https://discourse.julialang.org/t/problem-changing-variables-from-any-to-real/36116)

<div class="topic-metadata">

**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 10\
**Last updated:** [March 18, 2020, 3:41pm UTC](https://discourse.julialang.org/t/problem-changing-variables-from-any-to-real/36116 "2020-03-18T15:41:18Z")

</div>

I tried running this using XLSX df = DataFrame(XLSX.readtable("C:/Users/brett/OneDrive/Documents/FemData.xlsx", "Sheet1")...) for name in names(df) df\[!, name\] = identity.(df\[:, name\]) end print(df) It changed…

---

## [Indexing Nonlinear Expressions with nested indices in JuMP](https://discourse.julialang.org/t/indexing-nonlinear-expressions-with-nested-indices-in-jump/36140)

<div class="topic-metadata">

**Author:** [@shoshievass](https://discourse.julialang.org/u/shoshievass)\
**Replies:** 3\
**Last updated:** [March 18, 2020, 1:51pm UTC](https://discourse.julialang.org/t/indexing-nonlinear-expressions-with-nested-indices-in-jump/36140 "2020-03-18T13:51:11Z")

</div>

I’m trying to define a JuMP @NLexpression with embedded indexing and I need to use numerical indices instead of collections. I would have thought that the below would work but I’m getting an error saying that F was alrea…

---

## [Julia Database or CSV filtering](https://discourse.julialang.org/t/julia-database-or-csv-filtering/36104)

<div class="topic-metadata">

**Author:** [@bandaya](https://discourse.julialang.org/u/bandaya)\
**Replies:** 8\
**Last updated:** [March 18, 2020, 12:47pm UTC](https://discourse.julialang.org/t/julia-database-or-csv-filtering/36104 "2020-03-18T12:47:06Z")

</div>

Hi, I am using JuliaDB.jl package to upload CSV files but having problems with filtering or extracting some data. using JuliaDB # t = loadtable("MTab.csv") # Assume that the CSV contains the following data t = table(\[1,…

---

## [Why does LightGraphs.katz\_centrality give negative centrality scores?](https://discourse.julialang.org/t/why-does-lightgraphs-katz-centrality-give-negative-centrality-scores/21204)

<div class="topic-metadata">

**Author:** [@ennvvy](https://discourse.julialang.org/u/ennvvy)\
**Replies:** 1\
**Last updated:** [March 18, 2020, 3:40am UTC](https://discourse.julialang.org/t/why-does-lightgraphs-katz-centrality-give-negative-centrality-scores/21204 "2020-03-18T03:40:29Z")

</div>

I am using Katz\_centrality to determine the centrality measures for nodes in the network Julia 1.1.0. However, it yields negative values. Shouldn’t centrality scores be positive ?

---

## [Filtering DataFrame on String](https://discourse.julialang.org/t/filtering-dataframe-on-string/36117)

<div class="topic-metadata">

**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 2\
**Last updated:** [March 17, 2020, 10:56pm UTC](https://discourse.julialang.org/t/filtering-dataframe-on-string/36117 "2020-03-17T22:56:30Z")

</div>

Gahhhh… I show my ignorance. I have searched here and cannot quite get the answer. In the Kaggle covid-19 dataset I read covid\_19\_data.csv into a DataFrame The columns are: julia\> names(df) 8-element Array{Symbol,1}: …

---

## [JuMPv0.21 and deepcopy](https://discourse.julialang.org/t/jumpv0-21-and-deepcopy/36051)

<div class="topic-metadata">

**Author:** [@dmetivie](https://discourse.julialang.org/u/dmetivie)\
**Replies:** 7\
**Last updated:** [March 17, 2020, 5:03pm UTC](https://discourse.julialang.org/t/jumpv0-21-and-deepcopy/36051 "2020-03-17T17:03:17Z")

</div>

Hi, In JuMP Version 0.21 it says Calling deepcopy(::AbstractModel) now throws an error. Is there a new way to do deepcopy()? As far as I understand copy() is not what I want because the copied and original model are…

---

## [DSP.jl Resampled signal length doesn't match upsampling factor](https://discourse.julialang.org/t/dsp-jl-resampled-signal-length-doesnt-match-upsampling-factor/36036)

<div class="topic-metadata">

**Author:** [@meritwagner](https://discourse.julialang.org/u/meritwagner)\
**Replies:** 3\
**Last updated:** [March 17, 2020, 4:50pm UTC](https://discourse.julialang.org/t/dsp-jl-resampled-signal-length-doesnt-match-upsampling-factor/36036 "2020-03-17T16:50:31Z")

</div>

Hey guys, I ran into a problem, while trying out the resampling algorithm from the DSP package (v0.6.3). First I just create a test array with random numbers between 1 and 2. My plan is then to resample up by factor of…

[Previous page](https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=455)

[Next page](https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=457)