# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=541

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**Page:** 542

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## [Quadratic objective SDP](https://discourse.julialang.org/t/quadratic-objective-sdp/10003)

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**Author:** [@migarstka](https://discourse.julialang.org/u/migarstka)\
**Replies:** 1\
**Last updated:** [March 27, 2018, 4:38pm UTC](https://discourse.julialang.org/t/quadratic-objective-sdp/10003 "2018-03-27T16:38:44Z")

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I want to solve the following problem using either JuMP or Convex: \\min\_x \\quad x^TPx+2q^Tx+q^TPq\\\\ \\text{s.t.} \\quad \\text{mat}\\{x\\} \\in \\mathcal{S}\_+^n , where x \\in \\mathbb{R}^{n^2} is the vectorized decision vari…

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## [Learning Plots... now: marker\_z?](https://discourse.julialang.org/t/learning-plots-now-marker-z/9996)

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**Author:** [@BLI](https://discourse.julialang.org/u/BLI)\
**Replies:** 6\
**Last updated:** [March 27, 2018, 12:33pm UTC](https://discourse.julialang.org/t/learning-plots-now-marker-z/9996 "2018-03-27T12:33:23Z")

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I’m trying to learn Plots, and now: the marker\_z keyword. With xm=randn(100); ym=randn(100); the following two commands (pyplot backend) give almost the same plots: scatter(xm,ym) plot(xm,ym, markershape=:circle,li…

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## [3D line plots?](https://discourse.julialang.org/t/3d-line-plots/9921)

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**Author:** [@BLI](https://discourse.julialang.org/u/BLI)\
**Replies:** 3\
**Last updated:** [March 27, 2018, 1:39am UTC](https://discourse.julialang.org/t/3d-line-plots/9921 "2018-03-27T01:39:24Z")

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Yesterday, March 22, I did a 3D line plot using Plots/PyPlot: x = linspace(-2π,2π) plot(x,sin.(x),cos.(x)) This worked fine. Today, I did Pkg.update(), and re-ran the code. Doesn’t work, and I get long error message… …

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## [PostgreSQL.jl no longer works in v0.6](https://discourse.julialang.org/t/postgresql-jl-no-longer-works-in-v0-6/4581)

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**Author:** [@essenciary](https://discourse.julialang.org/u/essenciary)\
**Replies:** 27\
**Last updated:** [March 26, 2018, 4:05pm UTC](https://discourse.julialang.org/t/postgresql-jl-no-longer-works-in-v0-6/4581 "2018-03-26T16:05:44Z")

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Sadly, PostgreSQL.jl (https://github.com/JuliaDB/PostgreSQL.jl) has been lacking a maintainer for a year, and in Julia v0.6 is now dead as a dodo. I tried updating it in various occasions but in all honesty, low-level C…

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## [Problem with error reporting in Mocha](https://discourse.julialang.org/t/problem-with-error-reporting-in-mocha/9958)

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**Author:** [@Alejandro](https://discourse.julialang.org/u/Alejandro)\
**Replies:** 3\
**Last updated:** [March 26, 2018, 2:46am UTC](https://discourse.julialang.org/t/problem-with-error-reporting-in-mocha/9958 "2018-03-26T02:46:51Z")

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Hello. My name is Alejandro, nice to meet you all. On to business… I am a total Machine Learning novice beyond the theoretical aspect though now it seems I need to get to work in some applications if I am to actually ma…

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## [Decide and queue when core is available?](https://discourse.julialang.org/t/decide-and-queue-when-core-is-available/9949)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 5\
**Last updated:** [March 25, 2018, 2:43am UTC](https://discourse.julialang.org/t/decide-and-queue-when-core-is-available/9949 "2018-03-25T02:43:14Z")

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dear julia experts—I would like to queue tasks onto open CPU cores until one of my tasks has happened to find the correct solution. then I want to be done. In particular, I need to know how my master waits for many sla…

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## [Problem in cloning or adding OpenCV.jl](https://discourse.julialang.org/t/problem-in-cloning-or-adding-opencv-jl/9945)

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**Author:** [@tosalonijain](https://discourse.julialang.org/u/tosalonijain)\
**Replies:** 4\
**Last updated:** [March 24, 2018, 7:42pm UTC](https://discourse.julialang.org/t/problem-in-cloning-or-adding-opencv-jl/9945 "2018-03-24T19:42:40Z")

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julia\> Pkg.clone(“http://github.com/maxruby/OpenCV.jl”) INFO: Cloning OpenCV from http://github.com/maxruby/OpenCV.jl ERROR: OpenCV already exists Stacktrace: \[1\] clone(::String, ::SubString{String}) at ./pkg/entry.j…

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## [Quadratic Sieve and NFS factorization in Julia](https://discourse.julialang.org/t/quadratic-sieve-and-nfs-factorization-in-julia/9942)

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**Author:** [@Juan](https://discourse.julialang.org/u/Juan)\
**Replies:** 5\
**Last updated:** [March 24, 2018, 5:58pm UTC](https://discourse.julialang.org/t/quadratic-sieve-and-nfs-factorization-in-julia/9942 "2018-03-24T17:58:28Z")

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Hello. What’s the most advanced method used in primes.jl to factorize numbers? I’m looking for implementations of SIQS and NFS in Julia. I’ve only found this basic one of QS: https://github.com/hamukazu/quadratic\_sie…

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## [CUDAnative use multiple GPUs](https://discourse.julialang.org/t/cudanative-use-multiple-gpus/8274)

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**Author:** [@fnoelscher](https://discourse.julialang.org/u/fnoelscher)\
**Replies:** 5\
**Last updated:** [March 24, 2018, 1:15pm UTC](https://discourse.julialang.org/t/cudanative-use-multiple-gpus/8274 "2018-03-24T13:15:32Z")

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Hi, I am using julia on docker from maleadt/juliagpu and I’d like to use multiple GPUs, instead of one. The docs mention this: dev = CuDevice(0) CuContext(dev) do ctx # allocate things in this context @cuda ..…

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## [Uses of packages: JuliaDB, ExcelReaders, ExcelFiles and SymPy](https://discourse.julialang.org/t/uses-of-packages-juliadb-excelreaders-excelfiles-and-sympy/9920)

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**Author:** [@RaquelSantos](https://discourse.julialang.org/u/RaquelSantos)\
**Replies:** 4\
**Last updated:** [March 23, 2018, 7:13pm UTC](https://discourse.julialang.org/t/uses-of-packages-juliadb-excelreaders-excelfiles-and-sympy/9920 "2018-03-23T19:13:04Z")

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Whenever I try to install packages like: JuliaDB, ExcelReaders, ExcelFiles and SymPy, the program shows this message in the console: GitError (Code: ENOTFOUND, Class: Repository, Could not find repository from ‘DocString…

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## [Gtk, get coordinates of keypress](https://discourse.julialang.org/t/gtk-get-coordinates-of-keypress/9923)

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**Author:** [@Kurt\_Franke](https://discourse.julialang.org/u/Kurt_Franke)\
**Replies:** 1\
**Last updated:** [March 23, 2018, 4:53pm UTC](https://discourse.julialang.org/t/gtk-get-coordinates-of-keypress/9923 "2018-03-23T16:53:01Z")

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Hi, I’m trying to get a keypress to do something based on the mouse coordinate in a GtkCanvas widget. I can receive the keypress in the main GtkWindow, and I’d like to translate the coordinates with the library call gtk\_…

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## [ANN: Octo.jl: SQL Query DSL in Julia](https://discourse.julialang.org/t/ann-octo-jl-sql-query-dsl-in-julia/9912)

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**Author:** [@wookyoung](https://discourse.julialang.org/u/wookyoung)\
**Replies:** 2\
**Last updated:** [March 23, 2018, 1:53pm UTC](https://discourse.julialang.org/t/ann-octo-jl-sql-query-dsl-in-julia/9912 "2018-03-23T13:53:06Z")

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Hi. this package requires at least Julia 0.7-DEV, but I think that it needs some tests before to register the package. visit here and play SQL. https://github.com/wookay/Octo.jl Before using Repo, please install kind…

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## [Status of @tranform altering columns in DataFramesMeta](https://discourse.julialang.org/t/status-of-tranform-altering-columns-in-dataframesmeta/9904)

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**Author:** [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)\
**Replies:** 5\
**Last updated:** [March 22, 2018, 8:49pm UTC](https://discourse.julialang.org/t/status-of-tranform-altering-columns-in-dataframesmeta/9904 "2018-03-22T20:49:15Z")

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What is the status of altering a column that has already been altered in a @tranform block with DataFramesMeta? I have a dataframe with some messy descriptions in years and months in spanish, and I need to do some clean…

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## [Debugging, but code in conjugate gradient implementation. ](https://discourse.julialang.org/t/debugging-but-code-in-conjugate-gradient-implementation/9884)

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**Author:** [@Marcom](https://discourse.julialang.org/u/Marcom)\
**Replies:** 4\
**Last updated:** [March 22, 2018, 1:14pm UTC](https://discourse.julialang.org/t/debugging-but-code-in-conjugate-gradient-implementation/9884 "2018-03-22T13:14:51Z")

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Not sure this is the right place, but there seems to be an issue with how Julia is interpreting the inputs of a function. I am certain my code is correct as far as implementation of the problem statement. However, I keep…

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## [Using Julia with @parallel pmap or blank makes no difference in speed.](https://discourse.julialang.org/t/using-julia-with-parallel-pmap-or-blank-makes-no-difference-in-speed/9885)

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**Author:** [@Tillie](https://discourse.julialang.org/u/Tillie)\
**Replies:** 3\
**Last updated:** [March 22, 2018, 1:08pm UTC](https://discourse.julialang.org/t/using-julia-with-parallel-pmap-or-blank-makes-no-difference-in-speed/9885 "2018-03-22T13:08:23Z")

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Hi, the follwoing three test examples are minmal examples of my code. I do not understand why the speed is always the same. Moreover, Julia seems to use only one core. The whole CPU usage is only around 30%. If I us…

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## [Cross-correlation function in Julia vs. Python](https://discourse.julialang.org/t/cross-correlation-function-in-julia-vs-python/7573)

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**Author:** [@Duls91](https://discourse.julialang.org/u/Duls91)\
**Replies:** 12\
**Last updated:** [March 21, 2018, 7:29pm UTC](https://discourse.julialang.org/t/cross-correlation-function-in-julia-vs-python/7573 "2018-03-21T19:29:49Z")

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Hi there, I am new to Julia. I want to perform a cross-correlation with two 2d arrays (both 5X5). Using crosscor() (StatsBase.jl) returns a 9x5x5 array. What I would like is the cross-correlation matrix of dims M+N-1, s…

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## [Looking for guidance - signal processing team](https://discourse.julialang.org/t/looking-for-guidance-signal-processing-team/9855)

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**Author:** [@sirtom67](https://discourse.julialang.org/u/sirtom67)\
**Replies:** 1\
**Last updated:** [March 21, 2018, 11:44am UTC](https://discourse.julialang.org/t/looking-for-guidance-signal-processing-team/9855 "2018-03-21T11:44:58Z")

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Anyone interested in helping contribute to the DSP.jl project? I could use some help and guidance on how to contribute. The “esprit” function that I added this week finds the frequencies of sinusoidal signals: https://…

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## [distributed-memory QR / TSQR / linear algebra](https://discourse.julialang.org/t/distributed-memory-qr-tsqr-linear-algebra/9849)

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**Author:** [@nychiang](https://discourse.julialang.org/u/nychiang)\
**Replies:** 1\
**Last updated:** [March 20, 2018, 11:39pm UTC](https://discourse.julialang.org/t/distributed-memory-qr-tsqr-linear-algebra/9849 "2018-03-20T23:39:40Z")

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I’m looking for a distributed-memory parallel TSQR (tall and skinny QR) factorization package in Julia. However, it seems that there is no such implementation inside Julia, and what I can do is the following: — use MPI…

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## [\[ANN\] JDBC.jl Rejuvenated](https://discourse.julialang.org/t/ann-jdbc-jl-rejuvenated/9827)

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**Author:** [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Replies:** 3\
**Last updated:** [March 20, 2018, 2:01pm UTC](https://discourse.julialang.org/t/ann-jdbc-jl-rejuvenated/9827 "2018-03-20T14:01:48Z")

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Announcing JDBC.jl v0.3.0. This should provide you with a quick-and-easy way to get access to your databases with a Julia API almost immediately. It is very easy to get your data into a dataframe, for example using JD…

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## [Stepsize control in ODEProblem](https://discourse.julialang.org/t/stepsize-control-in-odeproblem/9772)

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**Author:** [@fedxa](https://discourse.julialang.org/u/fedxa)\
**Replies:** 11\
**Last updated:** [March 19, 2018, 1:31am UTC](https://discourse.julialang.org/t/stepsize-control-in-odeproblem/9772 "2018-03-19T01:31:29Z")

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Hello, I have a system of ODE, which is rather heterogeneous. That is one equation corresponds to some background property of a system, and then there are many (say, hundred) equations for individual evolution of compo…

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## [Solving a model and its modified copy](https://discourse.julialang.org/t/solving-a-model-and-its-modified-copy/9778)

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**Author:** [@varun7rs](https://discourse.julialang.org/u/varun7rs)\
**Replies:** 2\
**Last updated:** [March 18, 2018, 7:30pm UTC](https://discourse.julialang.org/t/solving-a-model-and-its-modified-copy/9778 "2018-03-18T19:30:08Z")

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As a follow-up to IainNZ’s comments on issue #399, I’ve slightly modified the code to experiment with variable fixings. While I only intend to fix variables of the object r, the fixings are applied to object p as well. I…

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## [CUDAnative ERROR: could not load library "libjulia.exe"](https://discourse.julialang.org/t/cudanative-error-could-not-load-library-libjulia-exe/9781)

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**Author:** [@Luxemecongineer](https://discourse.julialang.org/u/Luxemecongineer)\
**Replies:** 3\
**Last updated:** [March 18, 2018, 6:35pm UTC](https://discourse.julialang.org/t/cudanative-error-could-not-load-library-libjulia-exe/9781 "2018-03-18T18:35:03Z")

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I have passed tests of LLVM and CUDAdrv (non-documentation tests). But Pkg.test(“CUDAnative”) fails for ERROR: LoadError: could not load library "libjulia.exe" The specified module could not be found. Please, let me kn…

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## [BigFloat precision issue](https://discourse.julialang.org/t/bigfloat-precision-issue/9786)

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**Author:** [@vepiteski](https://discourse.julialang.org/u/vepiteski)\
**Replies:** 4\
**Last updated:** [March 18, 2018, 5:12pm UTC](https://discourse.julialang.org/t/bigfloat-precision-issue/9786 "2018-03-18T17:12:44Z")

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julia\> N=BigFloat(2.0,2048); julia\> S=sqrt(N); julia\> S^2-N -1.727233711018888925077270372560079914223200072887256277004740694033718360632485e-77 julia\> S.prec 256 julia\> N.prec 2048 Why only 256 precision from t…

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## [ANN: Docker image for CUDA packages](https://discourse.julialang.org/t/ann-docker-image-for-cuda-packages/5792)

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**Author:** [@maleadt](https://discourse.julialang.org/u/maleadt)\
**Replies:** 10\
**Last updated:** [March 18, 2018, 9:27am UTC](https://discourse.julialang.org/t/ann-docker-image-for-cuda-packages/5792 "2018-03-18T09:27:38Z")

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Hi all, Many JuliaGPU packages are pretty hard to install, so I’ve been working a little on a Docker image which comes with some CUDA packages preinstalled: maleadt/juliagpu, requiring nvidia-docker: $ docker pull male…

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## [Plotly Documentation and Examples](https://discourse.julialang.org/t/plotly-documentation-and-examples/9775)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 3\
**Last updated:** [March 17, 2018, 11:38pm UTC](https://discourse.julialang.org/t/plotly-documentation-and-examples/9775 "2018-03-17T23:38:26Z")

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I think pretty much most or all of the (introductory) examples at Plotly julia graphing library in Julia are broken at this point in 0.6.2. this is a pity—the outline and docs on their webpage look great. is there a ha…

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## [How to plot heatmap and contour plots in polar coordinates with Plots.jl?](https://discourse.julialang.org/t/how-to-plot-heatmap-and-contour-plots-in-polar-coordinates-with-plots-jl/7817)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 5\
**Last updated:** [March 17, 2018, 7:40am UTC](https://discourse.julialang.org/t/how-to-plot-heatmap-and-contour-plots-in-polar-coordinates-with-plots-jl/7817 "2018-03-17T07:40:09Z")

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It is really nice to have polar coordinates implemented in Plots.jl: using Plots; gr() plot(linspace(0,3π,100), rand(100), proj=:polar, m=:red) and even nicer to interact with them using the PlotlyJS backend. Howeve…

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## [How to link two widgets in InteractNext, WebIO?](https://discourse.julialang.org/t/how-to-link-two-widgets-in-interactnext-webio/9388)

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**Author:** [@jwikmark](https://discourse.julialang.org/u/jwikmark)\
**Replies:** 3\
**Last updated:** [March 16, 2018, 8:37pm UTC](https://discourse.julialang.org/t/how-to-link-two-widgets-in-interactnext-webio/9388 "2018-03-16T20:37:53Z")

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Suppose I have two sliders and I want the relationship x = 10-y to hold. I can do the following: using WebIO, InteractNext, Blink s = slider(0:10, label="x") t = slider(0:10, label="y") x = obs(s) y = obs(t) on(x) d…

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## [Eigenvalues problem in ApproxFun](https://discourse.julialang.org/t/eigenvalues-problem-in-approxfun/580)

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**Author:** [@mzaffalon](https://discourse.julialang.org/u/mzaffalon)\
**Replies:** 11\
**Last updated:** [March 16, 2018, 6:25pm UTC](https://discourse.julialang.org/t/eigenvalues-problem-in-approxfun/580 "2018-03-16T18:25:19Z")

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Is ApproxFun able to compute the eigenstates of a 1dimensional linear differential operator in the way Chebfun does? I assume not yet. I am interested in the Schroedinger equation. michele

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## [Using @NLexpression in JuMP within a loop](https://discourse.julialang.org/t/using-nlexpression-in-jump-within-a-loop/9751)

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**Author:** [@igorteo84](https://discourse.julialang.org/u/igorteo84)\
**Replies:** 0\
**Last updated:** [March 16, 2018, 4:25am UTC](https://discourse.julialang.org/t/using-nlexpression-in-jump-within-a-loop/9751 "2018-03-16T04:25:15Z")

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Hello, I’ve a JuMP related question and how to use @NLexpression within a loop mu is a JxN matrix that I’ve defined to be a variable in the MPEC model @variable(MPEC, mu\[j=1:J, n=1:N\], start=mu0\[j,n\]). v2 is a 5Tx100 …

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## [Why is source build Julia required to use GPU packages](https://discourse.julialang.org/t/why-is-source-build-julia-required-to-use-gpu-packages/9747)

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**Author:** [@cuchxq](https://discourse.julialang.org/u/cuchxq)\
**Replies:** 1\
**Last updated:** [March 15, 2018, 9:23pm UTC](https://discourse.julialang.org/t/why-is-source-build-julia-required-to-use-gpu-packages/9747 "2018-03-15T21:23:17Z")

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I am trying to use Julia GPU packages, and README files from juliaGPU GitHub repo all states that in order to use these packages, I need to build Julia from source. But why is that? Any help is appreciated! Thank you in …

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