# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=554

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**Page:** 555

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## [How is the max operator dealt with in DualNumbers.jl?](https://discourse.julialang.org/t/how-is-the-max-operator-dealt-with-in-dualnumbers-jl/5743)

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**Author:** [@vgdev](https://discourse.julialang.org/u/vgdev)\
**Replies:** 4\
**Last updated:** [September 6, 2017, 1:40pm UTC](https://discourse.julialang.org/t/how-is-the-max-operator-dealt-with-in-dualnumbers-jl/5743 "2017-09-06T13:40:34Z")

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I am minimizing an objective function using a local optimization algorithm and I am supplying it with the gradient generated by ForwardDiff. However, my objective function contains functionals including the max(x,0) oper…

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## [Is repeated calculations of eigenvalues without overwriting input matrix or allocating new arrays possible?](https://discourse.julialang.org/t/is-repeated-calculations-of-eigenvalues-without-overwriting-input-matrix-or-allocating-new-arrays-possible/5649)

<div class="topic-metadata">

**Author:** [@Sleort](https://discourse.julialang.org/u/Sleort)\
**Replies:** 8\
**Last updated:** [September 6, 2017, 3:28am UTC](https://discourse.julialang.org/t/is-repeated-calculations-of-eigenvalues-without-overwriting-input-matrix-or-allocating-new-arrays-possible/5649 "2017-09-06T03:28:18Z")

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In my simulation, I need to repeatedly update a few entries of a square matrix A and then calculate the corresponding eigenvalues \\lambda. Doing \\lambda = eigvals(A) will allocate new memory each time, while \\lambda = ei…

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## [How do computation while transferring data between processes](https://discourse.julialang.org/t/how-do-computation-while-transferring-data-between-processes/5722)

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**Author:** [@usefulhyun](https://discourse.julialang.org/u/usefulhyun)\
**Replies:** 0\
**Last updated:** [September 5, 2017, 8:50am UTC](https://discourse.julialang.org/t/how-do-computation-while-transferring-data-between-processes/5722 "2017-09-05T08:50:08Z")

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Hi, there I do data tranferring via RemoteChannel. But I found it is impossible that Julia process run sending, receiving and computation at once. RemoteChannel has its own process and its ID which is determined by an…

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## [Inappropriate memory allocation?](https://discourse.julialang.org/t/inappropriate-memory-allocation/5707)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 24\
**Last updated:** [September 4, 2017, 3:33pm UTC](https://discourse.julialang.org/t/inappropriate-memory-allocation/5707 "2017-09-04T15:33:42Z")

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I don’t know why this is happening, but this is what track-allocation is giving me: - """ - EuclideanDistance - - The Euclidean distance ||x-y||₂ - """ - struct Eucli…

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## [TopNode not defined when trying to use ParallelAccelerator](https://discourse.julialang.org/t/topnode-not-defined-when-trying-to-use-parallelaccelerator/5714)

<div class="topic-metadata">

**Author:** [@Naelson\_douglas](https://discourse.julialang.org/u/Naelson_douglas)\
**Replies:** 0\
**Last updated:** [September 4, 2017, 2:18pm UTC](https://discourse.julialang.org/t/topnode-not-defined-when-trying-to-use-parallelaccelerator/5714 "2017-09-04T14:18:48Z")

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Hello! I’m trying to use ParallelAccelerator(which depends on CompilerTools.jl) on top of Julia 5.2 as in the screenshot attached. But I’m getting the “TopNode not defined error”. I see this error was fixed on versio…

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## [ApproxFun failure](https://discourse.julialang.org/t/approxfun-failure/5704)

<div class="topic-metadata">

**Author:** [@chobbes](https://discourse.julialang.org/u/chobbes)\
**Replies:** 3\
**Last updated:** [September 4, 2017, 7:09am UTC](https://discourse.julialang.org/t/approxfun-failure/5704 "2017-09-04T07:09:52Z")

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In v6.0, using ApproxFun returns an error: INFO: Precompiling module ApproxFun. ERROR: LoadError: LoadError: Expected \`func\_signature = ...\` with func\_signature as a call Expr... got: f(g::Fun{S, T}) where {S, T \<: Rea…

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## [Is it possible to use @simd with multiple variable loop?](https://discourse.julialang.org/t/is-it-possible-to-use-simd-with-multiple-variable-loop/5701)

<div class="topic-metadata">

**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 5\
**Last updated:** [September 4, 2017, 12:05am UTC](https://discourse.julialang.org/t/is-it-possible-to-use-simd-with-multiple-variable-loop/5701 "2017-09-04T00:05:12Z")

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Any chance of something like the following work? @simd for i=1:10000, j=1:10000 # do something end

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## [Why can forwarddiff get gradient wrt. to multiple parameters in 1 function call?](https://discourse.julialang.org/t/why-can-forwarddiff-get-gradient-wrt-to-multiple-parameters-in-1-function-call/5698)

<div class="topic-metadata">

**Author:** [@vgdev](https://discourse.julialang.org/u/vgdev)\
**Replies:** 5\
**Last updated:** [September 3, 2017, 8:49pm UTC](https://discourse.julialang.org/t/why-can-forwarddiff-get-gradient-wrt-to-multiple-parameters-in-1-function-call/5698 "2017-09-03T20:49:04Z")

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I wonder how ForwardDiff.jl can compute the gradient wrt. to multiple parameters of a function my\_func(a,b,c,d,...) in one function evaluation? According to Giles, Michael B. “Monte Carlo evaluation of sensitivities in c…

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## [Matrix Addition with multithreads!](https://discourse.julialang.org/t/matrix-addition-with-multithreads/5674)

<div class="topic-metadata">

**Author:** [@usefulhyun](https://discourse.julialang.org/u/usefulhyun)\
**Replies:** 10\
**Last updated:** [September 2, 2017, 6:01am UTC](https://discourse.julialang.org/t/matrix-addition-with-multithreads/5674 "2017-09-02T06:01:41Z")

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Hi, there! I’d like to do matrix addition with multithreads. I can do matrix multiplication with multithreads via BLAS.set\_num\_threads(t). But I do not know how to do this with matrix addition. Can Anyone help me?

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## [Finite difference approximation using Calculus, getting the values f(x),f(x+e),f(x-e)](https://discourse.julialang.org/t/finite-difference-approximation-using-calculus-getting-the-values-f-x-f-x-e-f-x-e/5681)

<div class="topic-metadata">

**Author:** [@vgdev](https://discourse.julialang.org/u/vgdev)\
**Replies:** 1\
**Last updated:** [September 3, 2017, 1:10am UTC](https://discourse.julialang.org/t/finite-difference-approximation-using-calculus-getting-the-values-f-x-f-x-e-f-x-e/5681 "2017-09-03T01:10:17Z")

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I have a function f wich is slow to evaluate. So when doing finite differentiating by the use of Calculus.jl in order to approximate \\partial f/\\partial x \\approx \\frac{f(x-\\epsilon)-f(x)+f(x+\\epsilon)}{\\epsilon^2}, I a…

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## [Multi-Node Parallelism](https://discourse.julialang.org/t/multi-node-parallelism/5666)

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**Author:** [@garrett-hagemann](https://discourse.julialang.org/u/garrett-hagemann)\
**Replies:** 3\
**Last updated:** [September 2, 2017, 10:55pm UTC](https://discourse.julialang.org/t/multi-node-parallelism/5666 "2017-09-02T22:55:54Z")

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I’m attempting to use Julia in a multi-node environment. I’m using the Stampede 2 system at TACC. I followed the instructions found here: Building with Intel MKL on a KNL system to get a copy of Julia up and running on t…

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## [Build JuMP variable from array of tuples](https://discourse.julialang.org/t/build-jump-variable-from-array-of-tuples/5638)

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**Author:** [@bbrunaud](https://discourse.julialang.org/u/bbrunaud)\
**Replies:** 3\
**Last updated:** [September 2, 2017, 8:33am UTC](https://discourse.julialang.org/t/build-jump-variable-from-array-of-tuples/5638 "2017-09-02T08:33:39Z")

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Hello Let’s say that I have an array of tuples containing all the indices I need for a variable A = \[(:a1,:b1),(:a2,:b2)\] Now, I want to define a JuMP variable such that I can access x\[:a1,:b1\] for example. How do I a…

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## [Comparing DataFrames native API and Query](https://discourse.julialang.org/t/comparing-dataframes-native-api-and-query/5472)

<div class="topic-metadata">

**Author:** [@piever](https://discourse.julialang.org/u/piever)\
**Replies:** 4\
**Last updated:** [September 1, 2017, 5:57pm UTC](https://discourse.julialang.org/t/comparing-dataframes-native-api-and-query/5472 "2017-09-01T17:57:20Z")

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I’m trying to understand to what extent the functionality of Query.jl can replace data manipulations that are already implemented in the DataFrames.jl. So far I’m impressed with Query’s flexibility, but there are a coupl…

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## [Combining MySQL and Query](https://discourse.julialang.org/t/combining-mysql-and-query/5627)

<div class="topic-metadata">

**Author:** [@piever](https://discourse.julialang.org/u/piever)\
**Replies:** 4\
**Last updated:** [August 31, 2017, 11:24pm UTC](https://discourse.julialang.org/t/combining-mysql-and-query/5627 "2017-08-31T23:24:23Z")

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Is there a way to execute a Query.jl style Query directly on a MySQL database? Given that MySQL.jl gives an iterable tuple wiht MySQLRowIterator(con, command) I thought something like this could work: @from i in MySQLRo…

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## [HTTP.jl : response bodies truncated](https://discourse.julialang.org/t/http-jl-response-bodies-truncated/5659)

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**Author:** [@evanfields](https://discourse.julialang.org/u/evanfields)\
**Replies:** 2\
**Last updated:** [August 31, 2017, 9:26pm UTC](https://discourse.julialang.org/t/http-jl-response-bodies-truncated/5659 "2017-08-31T21:26:43Z")

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(I assume this is because I’m doing something wrong, but if it’s just a bug I can open an issue.) When using HTTP.jl and accessing a particular server, I find that all requests except the first lead to a truncated respo…

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## [Getting the reciprocal condition number when computing the reordered schur factorization](https://discourse.julialang.org/t/getting-the-reciprocal-condition-number-when-computing-the-reordered-schur-factorization/5653)

<div class="topic-metadata">

**Author:** [@blegat](https://discourse.julialang.org/u/blegat)\
**Replies:** 0\
**Last updated:** [August 31, 2017, 7:27am UTC](https://discourse.julialang.org/t/getting-the-reciprocal-condition-number-when-computing-the-reordered-schur-factorization/5653 "2017-08-31T07:27:44Z")

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When computing the reordered schur decomposition, LAPACK can optionally compute reciprocal condition numbers. Whether or not it does this computation depends on the JOB parameter. Currently, Julia sets this parameter to …

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## [More ticks in \`Plots.jl\`](https://discourse.julialang.org/t/more-ticks-in-plots-jl/5575)

<div class="topic-metadata">

**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 4\
**Last updated:** [August 29, 2017, 11:01am UTC](https://discourse.julialang.org/t/more-ticks-in-plots-jl/5575 "2017-08-29T11:01:01Z")

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Sometimes Plots.jl gives me too few ticks with some backends, especially GR, which is now my favourite. MWE: using Plots using StatPlots gr() # important x = linspace(0.2291313228541989, 0.3318750511155737, 100) plot(de…

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## [How to get started with GPU programming? OpenCL or CUDA?](https://discourse.julialang.org/t/how-to-get-started-with-gpu-programming-opencl-or-cuda/5441)

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**Author:** [@ttiveron](https://discourse.julialang.org/u/ttiveron)\
**Replies:** 7\
**Last updated:** [August 29, 2017, 10:29am UTC](https://discourse.julialang.org/t/how-to-get-started-with-gpu-programming-opencl-or-cuda/5441 "2017-08-29T10:29:29Z")

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Hello, Thank you for taking the time to read my post, I really appreciate it! I am currently a Windows using, C# developer, but have been learning Julia for some data research and personal projects. I want to learn how …

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## [The function to optimize in JuMP](https://discourse.julialang.org/t/the-function-to-optimize-in-jump/4964)

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**Author:** [@MCSikivie](https://discourse.julialang.org/u/MCSikivie)\
**Replies:** 24\
**Last updated:** [August 29, 2017, 2:03am UTC](https://discourse.julialang.org/t/the-function-to-optimize-in-jump/4964 "2017-08-29T02:03:09Z")

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Folks, my prior experience is mainly in Matlab and I’m new to Julia, so forgive me if my question is basic. I’ve written a likelihood function in Jupyter and want to maximize this function in JuMP. Since it’s 600 lines …

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## [Announcing DynamicalSystems.jl & Inviting for JuliaDynamics](https://discourse.julialang.org/t/announcing-dynamicalsystems-jl-inviting-for-juliadynamics/5613)

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**Author:** [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Replies:** 11\
**Last updated:** [August 28, 2017, 9:48pm UTC](https://discourse.julialang.org/t/announcing-dynamicalsystems-jl-inviting-for-juliadynamics/5613 "2017-08-28T21:48:31Z")

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Hi all. I have been working on a package on my free time that I have mentioned in a previous post in this category. Now it is at a decent state and has been accepted as a Julia package. It’s called DynamicalSystems.jl! W…

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## [Givens rotation based compact QR for sparse matrices](https://discourse.julialang.org/t/givens-rotation-based-compact-qr-for-sparse-matrices/5603)

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**Author:** [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)\
**Replies:** 4\
**Last updated:** [August 28, 2017, 7:03am UTC](https://discourse.julialang.org/t/givens-rotation-based-compact-qr-for-sparse-matrices/5603 "2017-08-28T07:03:49Z")

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Is there any implementation/API for the QR factorization based on Givens rotations that don’t produce the Q matrix but gives an API for applying the Givens rotations to a vector possibly after inverting/transposing them?…

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## [Is JuMPeR available for Julia v0.6.0?](https://discourse.julialang.org/t/is-jumper-available-for-julia-v0-6-0/5596)

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**Author:** [@gavelasq](https://discourse.julialang.org/u/gavelasq)\
**Replies:** 1\
**Last updated:** [August 27, 2017, 6:32pm UTC](https://discourse.julialang.org/t/is-jumper-available-for-julia-v0-6-0/5596 "2017-08-27T18:32:36Z")

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is JuMPeR available for Julia v0.6.0? I got an error in JuMP in the Pkg.checkout(“JuMP”) output saying that JuMPeR does not have an available version for Julia v0.6.0.

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## [Need help with Mamba.jl 🙄](https://discourse.julialang.org/t/need-help-with-mamba-jl-roll-eyes/5582)

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**Author:** [@KrishnaKanhaiya](https://discourse.julialang.org/u/KrishnaKanhaiya)\
**Replies:** 2\
**Last updated:** [August 26, 2017, 11:11pm UTC](https://discourse.julialang.org/t/need-help-with-mamba-jl-roll-eyes/5582 "2017-08-26T23:11:06Z")

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Hello everyone, I am using Stan and Mamba to write an API to find the distribution of the parameters of the differential equations. The API is using OrdinaryDiffEq, ParameterizedFunctions, DiffEqBayes, Mamba f1 = @od…

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## [I want to extract and convert to integer a column in a DataFrame](https://discourse.julialang.org/t/i-want-to-extract-and-convert-to-integer-a-column-in-a-dataframe/5566)

<div class="topic-metadata">

**Author:** [@Jean-Victor](https://discourse.julialang.org/u/Jean-Victor)\
**Replies:** 8\
**Last updated:** [August 26, 2017, 7:00pm UTC](https://discourse.julialang.org/t/i-want-to-extract-and-convert-to-integer-a-column-in-a-dataframe/5566 "2017-08-26T19:00:02Z")

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With Julia 0.5, I could do this: Calories=int(Nutrition\[2:11,2\]), where Nutrition is a DataFrame. With Julia 0.6, whatever I do of the kind spawns an ominous red box which floats over my program like a giant cloud in a…

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## [Mmapping a discontiguous file?](https://discourse.julialang.org/t/mmapping-a-discontiguous-file/2016)

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**Author:** [@tlnagy](https://discourse.julialang.org/u/tlnagy)\
**Replies:** 4\
**Last updated:** [August 26, 2017, 3:48am UTC](https://discourse.julialang.org/t/mmapping-a-discontiguous-file/2016 "2017-08-26T03:48:39Z")

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I’m writing a parser for OME-TIFFs, which are pretty large binary files with many sets of XY matrices (images) stored inside of them (I have a list of their offsets within each file). Another limitation is that these fil…

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## [Why is my ForwardDiff derivative caluculation 5x as slow as just evaluating the function, when allocations are just 2x?](https://discourse.julialang.org/t/why-is-my-forwarddiff-derivative-caluculation-5x-as-slow-as-just-evaluating-the-function-when-allocations-are-just-2x/5555)

<div class="topic-metadata">

**Author:** [@vgdev](https://discourse.julialang.org/u/vgdev)\
**Replies:** 10\
**Last updated:** [August 25, 2017, 3:50pm UTC](https://discourse.julialang.org/t/why-is-my-forwarddiff-derivative-caluculation-5x-as-slow-as-just-evaluating-the-function-when-allocations-are-just-2x/5555 "2017-08-25T15:50:16Z")

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So, I am trying to understand what impacts the speed of calculating the derivative of a function using ForwardDiff. I am evaluating the mean of several simulated paths of a stochastic variable. However, evaluating the de…

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## [Change Gtk widget background/font/border color](https://discourse.julialang.org/t/change-gtk-widget-background-font-border-color/5552)

<div class="topic-metadata">

**Author:** [@Loic\_Chappaz](https://discourse.julialang.org/u/Loic_Chappaz)\
**Replies:** 4\
**Last updated:** [August 25, 2017, 2:47pm UTC](https://discourse.julialang.org/t/change-gtk-widget-background-font-border-color/5552 "2017-08-25T14:47:01Z")

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Hi! We are building a GUI with Gtk.jl and we are using Notebook widgets to organize pages, and we have a couple nested Notebooks in there. To help track which tab/page is active, I would like to color the background of …

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## [Plotlyjs, electron, and exporting figures](https://discourse.julialang.org/t/plotlyjs-electron-and-exporting-figures/5507)

<div class="topic-metadata">

**Author:** [@ko56](https://discourse.julialang.org/u/ko56)\
**Replies:** 15\
**Last updated:** [August 23, 2017, 9:21pm UTC](https://discourse.julialang.org/t/plotlyjs-electron-and-exporting-figures/5507 "2017-08-23T21:21:28Z")

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I am using Julia 0.6 on FreeBSD with Plots.jl and plotly() for graphics. Is there a solution for exporting plots to pdf, say, which is less heavyweight than installing Electron? Electron does not work on FreeBSD. (I a…

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## [Plots: How to create a histogram such that sum of bar heights =1](https://discourse.julialang.org/t/plots-how-to-create-a-histogram-such-that-sum-of-bar-heights-1/5392)

<div class="topic-metadata">

**Author:** [@Seth\_Chandler](https://discourse.julialang.org/u/Seth_Chandler)\
**Replies:** 23\
**Last updated:** [August 23, 2017, 5:47pm UTC](https://discourse.julialang.org/t/plots-how-to-create-a-histogram-such-that-sum-of-bar-heights-1/5392 "2017-08-23T17:47:22Z")

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I want to use the Plots package to create a histogram such that the heights of the bars sum to one (preferably for each series). I was hopeful that normalize=true would do the trick, but its goal is to let the sum of th…

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## [SOS1 Constraints in Bonmin Solver - JuMP / AmplNLWriter](https://discourse.julialang.org/t/sos1-constraints-in-bonmin-solver-jump-amplnlwriter/5450)

<div class="topic-metadata">

**Author:** [@michaellindon](https://discourse.julialang.org/u/michaellindon)\
**Replies:** 7\
**Last updated:** [August 23, 2017, 12:56pm UTC](https://discourse.julialang.org/t/sos1-constraints-in-bonmin-solver-jump-amplnlwriter/5450 "2017-08-23T12:56:27Z")

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I would like to use Bonmin to perform MINLP. The model I have in mind has some SOS constraints of type 1. According to the bonmin documentation page 2, the B-BB algorithm accepts SOS1 constraints. When I try to solve th…

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