# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=455

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

**Page:** 456

---

## [Sampling from a normal distribution](https://discourse.julialang.org/t/sampling-from-a-normal-distribution/36848)

<div class="topic-metadata">

**Author:** [@samantp](https://discourse.julialang.org/u/samantp)\
**Replies:** 4\
**Last updated:** [April 1, 2020, 4:28pm UTC](https://discourse.julialang.org/t/sampling-from-a-normal-distribution/36848 "2020-04-01T16:28:11Z")

</div>

I am trying to draw 1000 random values from a normal distribution with a specific mean and standard deviation. Additionally, the values cannot be negative, which is an added constraint. To do this I have been trying to u…

---

## [Optim.jl - How to find local maxima of multivariate function](https://discourse.julialang.org/t/optim-jl-how-to-find-local-maxima-of-multivariate-function/36853)

<div class="topic-metadata">

**Author:** [@mthelm85](https://discourse.julialang.org/u/mthelm85)\
**Replies:** 3\
**Last updated:** [April 1, 2020, 4:21pm UTC](https://discourse.julialang.org/t/optim-jl-how-to-find-local-maxima-of-multivariate-function/36853 "2020-04-01T16:21:56Z")

</div>

Pardon my ignorance (if you’ve seen any recent posts of mine you’ll know I’ve been studying calculus lately) but I’m trying to understand how to find local maxima of a multivariate function with Optim.jl. Given the follo…

---

## [Partially empty 2d histogram Plots.jl](https://discourse.julialang.org/t/partially-empty-2d-histogram-plots-jl/36828)

<div class="topic-metadata">

**Author:** [@isentropic](https://discourse.julialang.org/u/isentropic)\
**Replies:** 2\
**Last updated:** [April 1, 2020, 7:48am UTC](https://discourse.julialang.org/t/partially-empty-2d-histogram-plots-jl/36828 "2020-04-01T07:48:05Z")

</div>

Attempting plotting a small circle in 2d histogram (with custom bins and limits), gives a natural result in pyplot: However, Plots for some reason gives blank pixels (same image):

---

## [Zygote: meaning of @adjoint add(a, b) = add(a, b), Δ -\> (Δ, Δ)](https://discourse.julialang.org/t/zygote-meaning-of-adjoint-add-a-b-add-a-b/36707)

<div class="topic-metadata">

**Author:** [@jaynick](https://discourse.julialang.org/u/jaynick)\
**Replies:** 4\
**Last updated:** [March 31, 2020, 11:18pm UTC](https://discourse.julialang.org/t/zygote-meaning-of-adjoint-add-a-b-add-a-b/36707 "2020-03-31T23:18:52Z")

</div>

The zygote landing page has the example @adjoint add(a, b) = add(a, b), Δ -\> (Δ, Δ) Can someone explain what the Δ -\> (Δ, Δ) means? I would have expected the derivatives to be 1,1.

---

## [Number of constraints](https://discourse.julialang.org/t/number-of-constraints/36798)

<div class="topic-metadata">

**Author:** [@angeloaliano1](https://discourse.julialang.org/u/angeloaliano1)\
**Replies:** 1\
**Last updated:** [March 31, 2020, 7:59pm UTC](https://discourse.julialang.org/t/number-of-constraints/36798 "2020-03-31T19:59:57Z")

</div>

Dear all, The command num\_constraints() can determine the number of equality constraints in a given model? How can I find this?

---

## [CuArrays v2.0.1 results in segmentation fault for LinearAlgebra.mul!](https://discourse.julialang.org/t/cuarrays-v2-0-1-results-in-segmentation-fault-for-linearalgebra-mul/36755)

<div class="topic-metadata">

**Author:** [@fedoroff](https://discourse.julialang.org/u/fedoroff)\
**Replies:** 4\
**Last updated:** [March 31, 2020, 7:56am UTC](https://discourse.julialang.org/t/cuarrays-v2-0-1-results-in-segmentation-fault-for-linearalgebra-mul/36755 "2020-03-31T07:56:51Z")

</div>

The following code with CuArrays v2.0.1 results in segmentation fault on my computer: import CuArrays import LinearAlgebra N = 1024 y = CuArrays.zeros(N) x = CuArrays.zeros(N) A = CuArrays.zeros((N, N)) LinearAlgebra…

---

## [Alternative to deprecated NetworkViz?](https://discourse.julialang.org/t/alternative-to-deprecated-networkviz/36713)

<div class="topic-metadata">

**Author:** [@Xarg](https://discourse.julialang.org/u/Xarg)\
**Replies:** 1\
**Last updated:** [March 31, 2020, 3:21am UTC](https://discourse.julialang.org/t/alternative-to-deprecated-networkviz/36713 "2020-03-31T03:21:12Z")

</div>

Hi, I’m looking to convert one of my R notebooks to Julia, and one of the packages I’m using is VisNetwork which gives me an interactive graph I can click on nodes to get additional information on, and drag them around. …

---

## [Trouble making a pivot table](https://discourse.julialang.org/t/trouble-making-a-pivot-table/36610)

<div class="topic-metadata">

**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 19\
**Last updated:** [March 30, 2020, 1:21pm UTC](https://discourse.julialang.org/t/trouble-making-a-pivot-table/36610 "2020-03-30T13:21:00Z")

</div>

df1 = DataFrame(XLSX.readtable("C:/Users/Brett/Documents/Soc332Assignment3.xlsx","TestData")...) #change everything to Float64 for name in names(df1) df1\[!, name\] = identity.(df1\[:, name\]) end #change everythin…

---

## [GraphPlot.jl: possible to change font family?](https://discourse.julialang.org/t/graphplot-jl-possible-to-change-font-family/36699)

<div class="topic-metadata">

**Author:** [@Igor\_Douven](https://discourse.julialang.org/u/Igor_Douven)\
**Replies:** 3\
**Last updated:** [March 30, 2020, 1:04pm UTC](https://discourse.julialang.org/t/graphplot-jl-possible-to-change-font-family/36699 "2020-03-30T13:04:28Z")

</div>

I’m using gplot() from the GraphPlot.jl package to plot a graph created with LightGraphs.jl. I’d like to change the font family used for the node labels, but can’t find in the documentation how to do that. Does anyone kn…

---

## [Multiple variable assignment and ODE solution extracting](https://discourse.julialang.org/t/multiple-variable-assignment-and-ode-solution-extracting/36647)

<div class="topic-metadata">

**Author:** [@jmaffi](https://discourse.julialang.org/u/jmaffi)\
**Replies:** 4\
**Last updated:** [March 30, 2020, 12:11pm UTC](https://discourse.julialang.org/t/multiple-variable-assignment-and-ode-solution-extracting/36647 "2020-03-30T12:11:33Z")

</div>

Hi there! I am quite new to Julia and have read manuals, tutorials, FAQs, and almost all question threads regarding the following, but have not yet found a solution. I have a system of 17 ordinary differential equation…

---

## [Modifying legend markersize/linelength of a Plots/PyPlot plot after creation](https://discourse.julialang.org/t/modifying-legend-markersize-linelength-of-a-plots-pyplot-plot-after-creation/36723)

<div class="topic-metadata">

**Author:** [@dapz](https://discourse.julialang.org/u/dapz)\
**Replies:** 0\
**Last updated:** [March 30, 2020, 9:03am UTC](https://discourse.julialang.org/t/modifying-legend-markersize-linelength-of-a-plots-pyplot-plot-after-creation/36723 "2020-03-30T09:03:25Z")

</div>

Hi, I’m using a lot Plots.jl as I like having the common interface, but right now using mostly the PyPlot backend. I don’t want to use directly PyPlot as I coded some Plots recipes that I use. I have trouble with the le…

---

## [Procedural Nonlinear Constaint Generation - String to NLconstraint](https://discourse.julialang.org/t/procedural-nonlinear-constaint-generation-string-to-nlconstraint/34799)

<div class="topic-metadata">

**Author:** [@r-b0](https://discourse.julialang.org/u/r-b0)\
**Replies:** 9\
**Last updated:** [March 30, 2020, 1:53am UTC](https://discourse.julialang.org/t/procedural-nonlinear-constaint-generation-string-to-nlconstraint/34799 "2020-03-30T01:53:29Z")

</div>

I am implementing a large scale nonlinear program solver using the JuMP interface to IPOPT. The Nonlinear Modeling section of JuMP v0.21.0 documentation clearly explicates that all expressions used in NLconstraint and N…

---

## [Zygote docs suggest flux is out of date?](https://discourse.julialang.org/t/zygote-docs-suggest-flux-is-out-of-date/36706)

<div class="topic-metadata">

**Author:** [@jaynick](https://discourse.julialang.org/u/jaynick)\
**Replies:** 0\
**Last updated:** [March 29, 2020, 11:14pm UTC](https://discourse.julialang.org/t/zygote-docs-suggest-flux-is-out-of-date/36706 "2020-03-29T23:14:26Z")

</div>

In the zygote docs it says However, implicit parameters exist mainly for compatibility with Flux’s current AD; it’s recommended to use the other approaches unless you need this, where implicit parameters refer to the s…

---

## [DataFrame by new columns containing arrays](https://discourse.julialang.org/t/dataframe-by-new-columns-containing-arrays/36614)

<div class="topic-metadata">

**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 13\
**Last updated:** [March 29, 2020, 1:59pm UTC](https://discourse.julialang.org/t/dataframe-by-new-columns-containing-arrays/36614 "2020-03-29T13:59:45Z")

</div>

In DataFrames we can do this: by(iris, :Species, \[:PetalLength, :SepalLength\] =\> x -\> (a=mean(x.PetalLength)/mean(x.SepalLength), b=sum(x.PetalLength))) 3×3 DataFrame │ Row │ Species │ a │ b …

---

## [(not julia) Help make PPE for Hospitals (3-D printer required)](https://discourse.julialang.org/t/not-julia-help-make-ppe-for-hospitals-3-d-printer-required/36648)

<div class="topic-metadata">

**Author:** [@anon92994695](https://discourse.julialang.org/u/anon92994695)\
**Replies:** 1\
**Last updated:** [March 29, 2020, 1:55am UTC](https://discourse.julialang.org/t/not-julia-help-make-ppe-for-hospitals-3-d-printer-required/36648 "2020-03-29T01:55:27Z")

</div>

Many hospitals especially in the USA are in dire need of PPE and may not get it on time given the pandemic. For instance University of Michigan Hospital is accepting 3-D printed face shields (Ann Arbor residents join eff…

---

## [Extended Slack PPL discussion](https://discourse.julialang.org/t/extended-slack-ppl-discussion/36623)

<div class="topic-metadata">

**Author:** [@cscherrer](https://discourse.julialang.org/u/cscherrer)\
**Replies:** 5\
**Last updated:** [March 28, 2020, 5:25pm UTC](https://discourse.julialang.org/t/extended-slack-ppl-discussion/36623 "2020-03-28T17:25:51Z")

</div>

Hi, there was a nice thread today on the Julia Slack PPL channel. Because it’s the free version, this will scroll into oblivion, so I thought I’d capture it for reference and in case it’s useful to anyone else: I had …

---

## [Solving an optimal control problem with Optim.jl](https://discourse.julialang.org/t/solving-an-optimal-control-problem-with-optim-jl/36635)

<div class="topic-metadata">

**Author:** [@roi.holtzman](https://discourse.julialang.org/u/roi.holtzman)\
**Replies:** 4\
**Last updated:** [March 28, 2020, 2:17pm UTC](https://discourse.julialang.org/t/solving-an-optimal-control-problem-with-optim-jl/36635 "2020-03-28T14:17:57Z")

</div>

I am trying to solve an optimal control problem in Julia. I tried using NLOptControl.jl and JuMP.jl but ran into some difficulties. See this post. Therefore I am trying to use Optim.jl as an optimizer. Since my optimiza…

---

## [Is there a way to speed up this implementation of BLSTM layer?](https://discourse.julialang.org/t/is-there-a-way-to-speed-up-this-implementation-of-blstm-layer/36429)

<div class="topic-metadata">

**Author:** [@Azamat](https://discourse.julialang.org/u/Azamat)\
**Replies:** 1\
**Last updated:** [March 28, 2020, 11:00am UTC](https://discourse.julialang.org/t/is-there-a-way-to-speed-up-this-implementation-of-blstm-layer/36429 "2020-03-28T11:00:46Z")

</div>

I have implemented the BLSTM layer for a batch of sequences input stored as a 3D array with dimensions ordered as \[features × time × batch\]. And I wonder if there is a faster way to implement it. I’m interested in the sp…

---

## [Bug when using DSDP versus SCS optimiser with JuMP](https://discourse.julialang.org/t/bug-when-using-dsdp-versus-scs-optimiser-with-jump/36554)

<div class="topic-metadata">

**Author:** [@tdp](https://discourse.julialang.org/u/tdp)\
**Replies:** 2\
**Last updated:** [March 28, 2020, 8:30am UTC](https://discourse.julialang.org/t/bug-when-using-dsdp-versus-scs-optimiser-with-jump/36554 "2020-03-28T08:30:04Z")

</div>

Hi, How do I resolve the error below generated when I run my code using the DSDP optimiser? I get the right answer, without errors, when I run my code using the SCS optimiser instead. (This question is a follow-up to t…

---

## [Where can I get detailed longitudinal data of the COVID-19 pandemics?](https://discourse.julialang.org/t/where-can-i-get-detailed-longitudinal-data-of-the-covid-19-pandemics/36577)

<div class="topic-metadata">

**Author:** [@Juan](https://discourse.julialang.org/u/Juan)\
**Replies:** 4\
**Last updated:** [March 27, 2020, 4:56pm UTC](https://discourse.julialang.org/t/where-can-i-get-detailed-longitudinal-data-of-the-covid-19-pandemics/36577 "2020-03-27T16:56:32Z")

</div>

Where can I download a full dataset of the SARS-CoV-2 pandemics containing time information for each individual (date of infection, date of death, age, gender, weight, censoring information…) It’s important to get this …

---

## [Installing Ipopt](https://discourse.julialang.org/t/installing-ipopt/35608)

<div class="topic-metadata">

**Author:** [@varun\_yaramasu](https://discourse.julialang.org/u/varun_yaramasu)\
**Replies:** 8\
**Last updated:** [March 27, 2020, 4:46pm UTC](https://discourse.julialang.org/t/installing-ipopt/35608 "2020-03-27T16:46:58Z")

</div>

julia\> Pkg.build("Ipopt") Building CodecZlib ─→ \`C:\\Users\\yaramasv\\.juliapro\\JuliaPro\_v1.3.1-1\\packages\\CodecZlib\\5t9zO\\deps\\build.log\` Building MbedTLS ───→ \`C:\\Users\\yaramasv\\.juliapro\\JuliaPro\_v1.3.1-1\\packages\\…

---

## [Point Julia to Cbc built from source](https://discourse.julialang.org/t/point-julia-to-cbc-built-from-source/36516)

<div class="topic-metadata">

**Author:** [@joshuastowell25](https://discourse.julialang.org/u/joshuastowell25)\
**Replies:** 5\
**Last updated:** [March 27, 2020, 3:30pm UTC](https://discourse.julialang.org/t/point-julia-to-cbc-built-from-source/36516 "2020-03-27T15:30:57Z")

</div>

Hello All, I am trying to get JuMP and Cbc to use multithreading. Turns out that in order to do this you have to build Cbc from source with the --enable-cbc-parallel option. I have followed the cbc build instructions i…

---

## [Convert model with anonymous variables to "readable" form](https://discourse.julialang.org/t/convert-model-with-anonymous-variables-to-readable-form/36594)

<div class="topic-metadata">

**Author:** [@richard046](https://discourse.julialang.org/u/richard046)\
**Replies:** 5\
**Last updated:** [March 27, 2020, 2:29pm UTC](https://discourse.julialang.org/t/convert-model-with-anonymous-variables-to-readable-form/36594 "2020-03-27T14:29:34Z")

</div>

Hello, I have a code(written by others) that builds a JuMP model, but I can’t see what are the constraints, becouse it has \_\_anon\_\_ variables, like this: Min \_\_anon\_\_ + \_\_anon\_\_ Subject to \_\_anon\_\_ - \_\_anon\_\_ == 0.5 …

---

## [Spearman Correlation, How do I find rho?](https://discourse.julialang.org/t/spearman-correlation-how-do-i-find-rho/36291)

<div class="topic-metadata">

**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 17\
**Last updated:** [March 27, 2020, 8:26am UTC](https://discourse.julialang.org/t/spearman-correlation-how-do-i-find-rho/36291 "2020-03-27T08:26:57Z")

</div>

B= df.Crude\_Birth\_Rate Employment\_df = DataFrame(A=df.Female\_Employment,B=df.Crude\_Birth\_Rate, )corspearman(x=A, y=B) = cor(tiedrank(A), tiedrank(B)) I’m trying to do a Spearman Correlation Test, because I know from my…

---

## [Using a Voronoi tessellation to represent a density field](https://discourse.julialang.org/t/using-a-voronoi-tessellation-to-represent-a-density-field/36585)

<div class="topic-metadata">

**Author:** [@arnauqb](https://discourse.julialang.org/u/arnauqb)\
**Replies:** 0\
**Last updated:** [March 27, 2020, 7:13am UTC](https://discourse.julialang.org/t/using-a-voronoi-tessellation-to-represent-a-density-field/36585 "2020-03-27T07:13:16Z")

</div>

Hi all, I have a set of 2D points (x,y) with a density value associated to them. I want to create a 2D density field from that, using a Voronoi tessellation. I am then interested to be able to query the density value fo…

---

## [Potential bug on relative gap calculation](https://discourse.julialang.org/t/potential-bug-on-relative-gap-calculation/36323)

<div class="topic-metadata">

**Author:** [@Diego](https://discourse.julialang.org/u/Diego)\
**Replies:** 3\
**Last updated:** [March 27, 2020, 2:54am UTC](https://discourse.julialang.org/t/potential-bug-on-relative-gap-calculation/36323 "2020-03-27T02:54:09Z")

</div>

Whatever the MIP tolerance I get the relative mip gap is always zero. I am using: MOI.get(model, MOI.RelativeGap()) JuMP v"0.20.1" Xpress v"0.10.0" Seems to be an issue either in JuMP or in Xpress

---

## [How to do Cross Tabs?](https://discourse.julialang.org/t/how-to-do-cross-tabs/36533)

<div class="topic-metadata">

**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 4\
**Last updated:** [March 26, 2020, 10:11pm UTC](https://discourse.julialang.org/t/how-to-do-cross-tabs/36533 "2020-03-26T22:11:19Z")

</div>

Is there a package to do Cross Tabulation? I have HypothesisTests and StatsBase, but can’t find anything about Cross Tabulation in the documentation for each.

---

## [Multivariate Correlation Tables-- Partial Correlation Tables](https://discourse.julialang.org/t/multivariate-correlation-tables-partial-correlation-tables/36566)

<div class="topic-metadata">

**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 0\
**Last updated:** [March 26, 2020, 8:03pm UTC](https://discourse.julialang.org/t/multivariate-correlation-tables-partial-correlation-tables/36566 "2020-03-26T20:03:23Z")

</div>

In there a way to automatically generarate partial correlation tables?

---

## [How do I add arguments to a frequency table?](https://discourse.julialang.org/t/how-do-i-add-arguments-to-a-frequency-table/36517)

<div class="topic-metadata">

**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 14\
**Last updated:** [March 26, 2020, 5:04pm UTC](https://discourse.julialang.org/t/how-do-i-add-arguments-to-a-frequency-table/36517 "2020-03-26T17:04:34Z")

</div>

I’m trying to do a frequency table with a data frame ‘df’ frequencytable(df) I get an error, argument not provided. What arguments do I need?

---

## [Scalar product in objective](https://discourse.julialang.org/t/scalar-product-in-objective/36550)

<div class="topic-metadata">

**Author:** [@ohmsweetohm1](https://discourse.julialang.org/u/ohmsweetohm1)\
**Replies:** 1\
**Last updated:** [March 26, 2020, 1:43pm UTC](https://discourse.julialang.org/t/scalar-product-in-objective/36550 "2020-03-26T13:43:51Z")

</div>

I’ll illustrate the problem with the following simple example: import JuMP l = ones(4) model= JuMP.Model() JuMP.@variable(model, x) JuMP.@variable(model, y1) JuMP.@variable(model, y2) epxr = \[ JuMP.@expression(model…

[Previous page](https://discourse.julialang.org/c/domain/10.md?page=454)

[Next page](https://discourse.julialang.org/c/domain/10.md?page=456)