# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=457

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**Page:** 458

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## [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)

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**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")

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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…

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

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**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")

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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…

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

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**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")

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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…

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## [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)

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**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")

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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)…

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

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**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")

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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…

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## [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)

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**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")

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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…

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

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**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")

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

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

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**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")

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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:…

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## [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)

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**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")

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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…

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

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**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")

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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,…

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

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**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")

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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…

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

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**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")

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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…

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

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**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")

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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…

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

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**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")

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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…

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## [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)

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**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")

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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 …

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

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**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")

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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…

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

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**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")

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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…

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## [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)

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**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")

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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…

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

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**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")

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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…

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

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**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")

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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…

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

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**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")

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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,…

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

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**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")

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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 ?

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

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**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")

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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}: …

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

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**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")

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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…

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## [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)

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**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")

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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…

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## [How to call nonlinear solver in MathOptInterface](https://discourse.julialang.org/t/how-to-call-nonlinear-solver-in-mathoptinterface/36001)

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**Author:** [@zxjroger](https://discourse.julialang.org/u/zxjroger)\
**Replies:** 3\
**Last updated:** [March 17, 2020, 3:06pm UTC](https://discourse.julialang.org/t/how-to-call-nonlinear-solver-in-mathoptinterface/36001 "2020-03-17T15:06:53Z")

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I am trying to move from MathProgBase to MathOptInterface. My code works for the former package, but after I rewrote it using the latter package, I got an error saying Ipopt: Failed to construct problem. I believe it is …

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## [2-dimensional DataFrame column](https://discourse.julialang.org/t/2-dimensional-dataframe-column/36060)

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**Author:** [@martincornejo](https://discourse.julialang.org/u/martincornejo)\
**Replies:** 2\
**Last updated:** [March 17, 2020, 3:05pm UTC](https://discourse.julialang.org/t/2-dimensional-dataframe-column/36060 "2020-03-17T15:05:32Z")

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MATLAB-tables and pandas-dataframe enable more than one element per cell (column-row pair). Is the same possible in Julia DataFrames? I tried for example: julia\> df = DataFrame(A = ones(10), B = ones(10,2)) which promp…

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## [\`empty!\` for JuMP.Model or JuMP.direct\_model?](https://discourse.julialang.org/t/empty-for-jump-model-or-jump-direct-model/35673)

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**Author:** [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Replies:** 12\
**Last updated:** [March 17, 2020, 3:03am UTC](https://discourse.julialang.org/t/empty-for-jump-model-or-jump-direct-model/35673 "2020-03-17T03:03:19Z")

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I did not found a way of emptying a model (created with either JuMP.model or JuMP.direct\_model). There is a MathOptInterface.empty!, but it seems I need to call it over backend(model) and after I do that, I cannot add a…

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## [JuMP-dev 2020](https://discourse.julialang.org/t/jump-dev-2020/33158)

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**Author:** [@odow](https://discourse.julialang.org/u/odow)\
**Replies:** 2\
**Last updated:** [March 16, 2020, 7:43pm UTC](https://discourse.julialang.org/t/jump-dev-2020/33158 "2020-03-16T19:43:00Z")

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Dear all, We are pleased to announce that we are now inviting talk submissions for JuMP-dev 2020, to be held June 15-17, 2020 in Louvain-la-Neuve, Belgium, in conjunction with UCLouvain. For more information on JuMP-de…

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## [VegaLite: Text labels on bar charts](https://discourse.julialang.org/t/vegalite-text-labels-on-bar-charts/36048)

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**Author:** [@hellemo](https://discourse.julialang.org/u/hellemo)\
**Replies:** 2\
**Last updated:** [March 16, 2020, 6:38pm UTC](https://discourse.julialang.org/t/vegalite-text-labels-on-bar-charts/36048 "2020-03-16T18:38:04Z")

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I can’t figure out how to show the actual values on a bar chart in VegaLite, I tried adapting the examples but clearly I don’t understand what options are necessary to achieve what I want. I’m able to do each layer more…

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