# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=298

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**Page:** 299

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## [Eigenvectors of a symmetric tensor and a matrix](https://discourse.julialang.org/t/eigenvectors-of-a-symmetric-tensor-and-a-matrix/77604)

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**Author:** [@FrootLoops](https://discourse.julialang.org/u/FrootLoops)\
**Replies:** 2\
**Last updated:** [March 8, 2022, 8:09pm UTC](https://discourse.julialang.org/t/eigenvectors-of-a-symmetric-tensor-and-a-matrix/77604 "2022-03-08T20:09:35Z")

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Hi, I have a problem calculating the eigenvectors of a matrix/tensor. Maybe someone can explain why the outputs differ from each other. using LinearAlgebra, Tensors A = \[-24.978551803697826 -51.42238499537693 0.0; -51…

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## [Social Media Mapping](https://discourse.julialang.org/t/social-media-mapping/77605)

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**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 0\
**Last updated:** [March 8, 2022, 7:25pm UTC](https://discourse.julialang.org/t/social-media-mapping/77605 "2022-03-08T19:25:18Z")

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Is there anyone that has experience making maps of social networks, by friends or by posts?

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## [Stratified and weighted sampling in dataframes](https://discourse.julialang.org/t/stratified-and-weighted-sampling-in-dataframes/77565)

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**Author:** [@George\_Githinji](https://discourse.julialang.org/u/George_Githinji)\
**Replies:** 8\
**Last updated:** [March 8, 2022, 7:11pm UTC](https://discourse.julialang.org/t/stratified-and-weighted-sampling-in-dataframes/77565 "2022-03-08T19:11:37Z")

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I have a function that can take a random sample from a dataframe. However I ran into an issue when working with grouped a dataframe in which case I have grouped the data by several columns and I would like to sample with…

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## [Tuning the gamma parameter in FrankWolfe.jl](https://discourse.julialang.org/t/tuning-the-gamma-parameter-in-frankwolfe-jl/77023)

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**Author:** [@dridz](https://discourse.julialang.org/u/dridz)\
**Replies:** 7\
**Last updated:** [March 8, 2022, 5:47pm UTC](https://discourse.julialang.org/t/tuning-the-gamma-parameter-in-frankwolfe-jl/77023 "2022-03-08T17:47:33Z")

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Hi, I found out about the FrankWolfe.jl package and it looks great ! I am dealing with an optimization problem for which I have a lot of intuition about a good warm start and also about the order of magnitude of a good …

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## [Scalar indexing error when loading MNIST](https://discourse.julialang.org/t/scalar-indexing-error-when-loading-mnist/77496)

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**Author:** [@TheLateKronos](https://discourse.julialang.org/u/TheLateKronos)\
**Replies:** 2\
**Last updated:** [March 8, 2022, 5:37pm UTC](https://discourse.julialang.org/t/scalar-indexing-error-when-loading-mnist/77496 "2022-03-08T17:37:14Z")

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The following code in a fresh session produces a scalar indexing error: using Flux using MLDatasets categories = 0:9 xtrain, ytrain = MNIST.traindata(Float32) xtest, ytest = MNIST.testdata(Float32) ytrain, ytest = Flu…

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## [How to print multiple values in a loop](https://discourse.julialang.org/t/how-to-print-multiple-values-in-a-loop/77474)

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**Author:** [@Eric.O](https://discourse.julialang.org/u/Eric.O)\
**Replies:** 8\
**Last updated:** [March 8, 2022, 4:48pm UTC](https://discourse.julialang.org/t/how-to-print-multiple-values-in-a-loop/77474 "2022-03-08T16:48:05Z")

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I want to print my output in Julia, I have written it in the form presented below but I want to use a for loop to make it more concise. Any help on how to write the code below using for loop will be appreciated please. …

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## [MPI on Raspberry pi distributed computer](https://discourse.julialang.org/t/mpi-on-raspberry-pi-distributed-computer/77588)

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**Author:** [@Isonoglu](https://discourse.julialang.org/u/Isonoglu)\
**Replies:** 1\
**Last updated:** [March 8, 2022, 3:28pm UTC](https://discourse.julialang.org/t/mpi-on-raspberry-pi-distributed-computer/77588 "2022-03-08T15:28:51Z")

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Hello everyone. I’m a total beginner in Julia and cluster computing. I have already made a Raspberry pi distributed computer with 4 nodes. Any node can SSH to every other. Every node should perform some calculations “loc…

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## [Finding crossing points of two vectors of vertices](https://discourse.julialang.org/t/finding-crossing-points-of-two-vectors-of-vertices/15786)

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**Author:** [@jcook](https://discourse.julialang.org/u/jcook)\
**Replies:** 15\
**Last updated:** [March 8, 2022, 12:54pm UTC](https://discourse.julialang.org/t/finding-crossing-points-of-two-vectors-of-vertices/15786 "2022-03-08T12:54:32Z")

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Is there a tool out there that is able to find the locations of where two lines cross one another? By line I mean a vector of positions in the 2D plane, where the positions are connected by straight lines. I would prefer…

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## [Default norm used in ODE error control](https://discourse.julialang.org/t/default-norm-used-in-ode-error-control/70995)

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**Author:** [@Bernard\_GODARD](https://discourse.julialang.org/u/Bernard_GODARD)\
**Replies:** 4\
**Last updated:** [March 8, 2022, 1:47pm UTC](https://discourse.julialang.org/t/default-norm-used-in-ode-error-control/70995 "2022-03-08T13:47:41Z")

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The error control in DifferentialEquations using the default internal norm is as follow: Compute tolerance on i-th component: tolerance\_i = absoluteTolerance\_i + relativeTolerance\_i \* max( \\lvert previousState\_i \\rver…

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## [CBC solver](https://discourse.julialang.org/t/cbc-solver/77548)

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**Author:** [@Francisco\_Javier\_Mar](https://discourse.julialang.org/u/Francisco_Javier_Mar)\
**Replies:** 18\
**Last updated:** [March 8, 2022, 1:08pm UTC](https://discourse.julialang.org/t/cbc-solver/77548 "2022-03-08T13:08:01Z")

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I got this error while trying to test Alpine: Failed to precompile Cbc. What can I do to fix this ? Any suggestion ? My Julia version: JuliaPro\_v1.5.3-1

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## [Powermodels.jl SCS for a mixed-integer problem with SDP relaxation](https://discourse.julialang.org/t/powermodels-jl-scs-for-a-mixed-integer-problem-with-sdp-relaxation/77244)

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**Author:** [@lostamcimber](https://discourse.julialang.org/u/lostamcimber)\
**Replies:** 4\
**Last updated:** [March 8, 2022, 12:44pm UTC](https://discourse.julialang.org/t/powermodels-jl-scs-for-a-mixed-integer-problem-with-sdp-relaxation/77244 "2022-03-08T12:44:23Z")

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Hi all, I am trying to solve a mixed integer problem of a network with switches (switches are my binary variables). I can solve my OPF problem with quadratic relaxations like ‘SOCWRPowerModel’, ‘QCRMPowerModel’, ‘QCLSPo…

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## [GPU computing on AMD consumer hardware?](https://discourse.julialang.org/t/gpu-computing-on-amd-consumer-hardware/53841)

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**Author:** [@tp2750](https://discourse.julialang.org/u/tp2750)\
**Replies:** 11\
**Last updated:** [March 8, 2022, 12:40pm UTC](https://discourse.julialang.org/t/gpu-computing-on-amd-consumer-hardware/53841 "2022-03-08T12:40:55Z")

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I’m putting together a new computer and would like to be able to experiment with GPU computing in Julia (on Ubuntu). I would greatly prefer an AMD GPU because of the in-kernel driver support on Linux. My understanding i…

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## [How to add grid lines on top of a heatmap in Makie?](https://discourse.julialang.org/t/how-to-add-grid-lines-on-top-of-a-heatmap-in-makie/77578)

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**Author:** [@ForceBru](https://discourse.julialang.org/u/ForceBru)\
**Replies:** 2\
**Last updated:** [March 8, 2022, 12:30pm UTC](https://discourse.julialang.org/t/how-to-add-grid-lines-on-top-of-a-heatmap-in-makie/77578 "2022-03-08T12:30:52Z")

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I have some code which boils down to heatmap(matrix, colormap=Reverse(:grays)) and produces this plot: There’s a lot of white in the plot, and I’d like to emphasize that it’s not empty space, so I wanted to add grid …

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## [Solving KKT linear system (which solver for LDLᵀ factorization?)](https://discourse.julialang.org/t/solving-kkt-linear-system-which-solver-for-ldl-factorization/77544)

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**Author:** [@zdenek\_hurak](https://discourse.julialang.org/u/zdenek_hurak)\
**Replies:** 3\
**Last updated:** [March 8, 2022, 8:47am UTC](https://discourse.julialang.org/t/solving-kkt-linear-system-which-solver-for-ldl-factorization/77544 "2022-03-08T08:47:48Z")

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I would like to solve a system of linear equations given in a vector form as \\begin{bmatrix} Q & A^\\top \\\\ A & 0\\end{bmatrix}\\begin{bmatrix}x\\\\ \\lambda\\end{bmatrix} = \\begin{bmatrix} c \\\\ -b \\end{bmatrix} The matrix Q…

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## [How to standardize arrays in Julia?](https://discourse.julialang.org/t/how-to-standardize-arrays-in-julia/54046)

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**Author:** [@Shazman](https://discourse.julialang.org/u/Shazman)\
**Replies:** 7\
**Last updated:** [March 8, 2022, 7:46am UTC](https://discourse.julialang.org/t/how-to-standardize-arrays-in-julia/54046 "2022-03-08T07:46:16Z")

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I have two arrays (m and n) and each has one column with 100 elements. the first array is sampled from a normal distribution with mean 0 and standard deviation 1, the second one is sampled from a normal distribution with…

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## [Neos Server](https://discourse.julialang.org/t/neos-server/77549)

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**Author:** [@Francisco\_Javier\_Mar](https://discourse.julialang.org/u/Francisco_Javier_Mar)\
**Replies:** 1\
**Last updated:** [March 8, 2022, 2:19am UTC](https://discourse.julialang.org/t/neos-server/77549 "2022-03-08T02:19:13Z")

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I got this error while trying to install NEOSServer. What can I do ? ERROR: Unsatisfiable requirements detected for package HTTP \[cd3eb016\]: HTTP \[cd3eb016\] log: ├─possible versions are: \[0.6.10-0.6.14, 0.7.0-0.7.1, 0…

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## [Automotive/EV projects/packages?](https://discourse.julialang.org/t/automotive-ev-projects-packages/77533)

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**Author:** [@airpmb](https://discourse.julialang.org/u/airpmb)\
**Replies:** 2\
**Last updated:** [March 7, 2022, 7:46pm UTC](https://discourse.julialang.org/t/automotive-ev-projects-packages/77533 "2022-03-07T19:46:56Z")

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So I’m looking to dabble a bit with data from an OBD2 scanner, mostly to explore aspects of my EV’s energy consumption, and/or something about how the charging infrastructure is evolving, if I can find an appropriate API…

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## [CUDA.jl initialization test failing](https://discourse.julialang.org/t/cuda-jl-initialization-test-failing/77526)

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**Author:** [@RonRahaman](https://discourse.julialang.org/u/RonRahaman)\
**Replies:** 1\
**Last updated:** [March 7, 2022, 5:56pm UTC](https://discourse.julialang.org/t/cuda-jl-initialization-test-failing/77526 "2022-03-07T17:56:06Z")

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Hi all, I’m running tests for CUDA.jl (\]test CUDA) and I have one test failing. Should I be concerned, or can I safely ignore it? Error in testset initialization: Test Failed at /usr/local/pace-apps/manual/packages/jul…

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## [OneNote/Microsoft Graph API](https://discourse.julialang.org/t/onenote-microsoft-graph-api/76264)

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**Author:** [@airpmb](https://discourse.julialang.org/u/airpmb)\
**Replies:** 0\
**Last updated:** [February 11, 2022, 6:05pm UTC](https://discourse.julialang.org/t/onenote-microsoft-graph-api/76264 "2022-02-11T18:05:59Z")

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Has anyone experimented at all with the OneNote REST API?

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## [Error using system CUDA in CUDA.jl](https://discourse.julialang.org/t/error-using-system-cuda-in-cuda-jl/77423)

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**Author:** [@RonRahaman](https://discourse.julialang.org/u/RonRahaman)\
**Replies:** 3\
**Last updated:** [March 7, 2022, 4:19pm UTC](https://discourse.julialang.org/t/error-using-system-cuda-in-cuda-jl/77423 "2022-03-07T16:19:17Z")

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Hi all, I’m trying to install CUDA.jl using my system’s CUDA toolkit. The installation completes, but I get errors when I try to test it by running CUDA.version(). I set JULIA\_CUDA\_USE\_BINARYBUILDER=false and ensured t…

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## [Start using Molly.jl: place\_atoms not defined in module Molly?](https://discourse.julialang.org/t/start-using-molly-jl-place-atoms-not-defined-in-module-molly/77521)

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**Author:** [@ziolai](https://discourse.julialang.org/u/ziolai)\
**Replies:** 3\
**Last updated:** [March 7, 2022, 4:14pm UTC](https://discourse.julialang.org/t/start-using-molly-jl-place-atoms-not-defined-in-module-molly/77521 "2022-03-07T16:14:53Z")

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I started looking into Molly.jl and attempting to run one its examples. I get the error described below. Insight would be nice to receive. Thx! julia\> using Molly julia\> n\_atoms = 100 100 julia\> atom\_mass = 10.0u"u" …

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## [Concrete Operators in DiffEqOperators.jl for time-indepedent problems](https://discourse.julialang.org/t/concrete-operators-in-diffeqoperators-jl-for-time-indepedent-problems/77415)

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**Author:** [@ziolai](https://discourse.julialang.org/u/ziolai)\
**Replies:** 9\
**Last updated:** [March 7, 2022, 3:31pm UTC](https://discourse.julialang.org/t/concrete-operators-in-diffeqoperators-jl-for-time-indepedent-problems/77415 "2022-03-07T15:31:59Z")

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We are looking into the use of DiffEqOperators for time-independent problems. We are considering the Poisson equation on the unit interval and unit square. First a 1D implementation was made to figure out how to use it. …

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## [Outdated / bogus CUDA.jl documentation at https://juliagpu.gitlab.io/CUDA.jl?](https://discourse.julialang.org/t/outdated-bogus-cuda-jl-documentation-at-https-juliagpu-gitlab-io-cuda-jl/77515)

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**Author:** [@complyue](https://discourse.julialang.org/u/complyue)\
**Replies:** 1\
**Last updated:** [March 7, 2022, 3:13pm UTC](https://discourse.julialang.org/t/outdated-bogus-cuda-jl-documentation-at-https-juliagpu-gitlab-io-cuda-jl/77515 "2022-03-07T15:13:49Z")

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By CUDA.jl - Google Search , the first hit is the github repo, which is good, but the second hit is https://juliagpu.gitlab.io/CUDA.jl , which seems outdated, compared to https://cuda.juliagpu.org . But the later doesn’t…

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## [Stencil operations and Symbolics.jl](https://discourse.julialang.org/t/stencil-operations-and-symbolics-jl/75685)

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**Author:** [@vlc](https://discourse.julialang.org/u/vlc)\
**Replies:** 1\
**Last updated:** [March 7, 2022, 3:11pm UTC](https://discourse.julialang.org/t/stencil-operations-and-symbolics-jl/75685 "2022-03-07T15:11:36Z")

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Hi there, I’m writing a little package that solves classical PDEs on Cartesian grids, and am seeking advice on how to leverage Symbolics.jl to speed up operations such as matrix-vector products. As a MWE, I’ll focus on…

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## [Zygote and TimerOutputs, derivative of timed function](https://discourse.julialang.org/t/zygote-and-timeroutputs-derivative-of-timed-function/44234)

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**Author:** [@racinmat](https://discourse.julialang.org/u/racinmat)\
**Replies:** 3\
**Last updated:** [March 7, 2022, 12:45pm UTC](https://discourse.julialang.org/t/zygote-and-timeroutputs-derivative-of-timed-function/44234 "2022-03-07T12:45:00Z")

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Hi, sometimes I want to benchmark my code on my neural networks, especially their forward pass, using TimerOutputs.jl, but I don’t want to comment out all this when calculating gradients. Currently it’s crashing, not b…

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## [Make this more efficient?](https://discourse.julialang.org/t/make-this-more-efficient/77104)

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**Author:** [@r0b0ty](https://discourse.julialang.org/u/r0b0ty)\
**Replies:** 11\
**Last updated:** [March 7, 2022, 12:37pm UTC](https://discourse.julialang.org/t/make-this-more-efficient/77104 "2022-03-07T12:37:52Z")

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Hello, all. I have a DataFrame column, df.polygons, with strings of ten numbers separated by commas as shown below julia\> df.polygons 400000-element Vector{String}: “79,8,79.09999999999999,8,79.09999999999999,7.9,79…

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## [JuMP Hessian sparcity issues. Registered function's Hessians. atan2 issue](https://discourse.julialang.org/t/jump-hessian-sparcity-issues-registered-functions-hessians-atan2-issue/76342)

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**Author:** [@a6a3uh](https://discourse.julialang.org/u/a6a3uh)\
**Replies:** 6\
**Last updated:** [March 7, 2022, 5:43am UTC](https://discourse.julialang.org/t/jump-hessian-sparcity-issues-registered-functions-hessians-atan2-issue/76342 "2022-03-07T05:43:28Z")

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So there are a bunch of observations so far which I want to get some insights into. I’m describing issues with nonlinear solver btw. As soon as I’m using atan with 2 arguments JuMP seems registers this function for me (…

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## [Julia on Google Colab: Free GPU-Accelerated Shareable Notebooks](https://discourse.julialang.org/t/julia-on-google-colab-free-gpu-accelerated-shareable-notebooks/15319)

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**Author:** [@jekbradbury](https://discourse.julialang.org/u/jekbradbury)\
**Replies:** 58\
**Last updated:** [March 7, 2022, 4:26am UTC](https://discourse.julialang.org/t/julia-on-google-colab-free-gpu-accelerated-shareable-notebooks/15319 "2022-03-07T04:26:21Z")

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(Disclosure: While I work for Google, this is not an official Google product or announcement.) tl;dr: For Julia on Colab with GPUs, first open this notebook and run the cell (takes ~15-20 minutes), then open this one to…

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## [Convert DataFrameRow to Vector](https://discourse.julialang.org/t/convert-dataframerow-to-vector/77390)

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**Author:** [@Frankiewaang](https://discourse.julialang.org/u/Frankiewaang)\
**Replies:** 6\
**Last updated:** [March 6, 2022, 8:55pm UTC](https://discourse.julialang.org/t/convert-dataframerow-to-vector/77390 "2022-03-06T20:55:49Z")

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Hi Guys, I got a super easy question: when I want to convert a DataFrameRow with the same type to a Vector, I saw from some thread to use: Vector(data\[1,:\]) #or convert(Vector, data\[1,:\]) but some times I got the er…

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## [Optimizing using objective with an integral in it](https://discourse.julialang.org/t/optimizing-using-objective-with-an-integral-in-it/77162)

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**Author:** [@samerb](https://discourse.julialang.org/u/samerb)\
**Replies:** 5\
**Last updated:** [March 5, 2022, 11:05pm UTC](https://discourse.julialang.org/t/optimizing-using-objective-with-an-integral-in-it/77162 "2022-03-05T23:05:41Z")

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I’m new to JuMP and I’d like to minimize a function that has an integral in it. Here’s an example f(y) = \\int\_0^y y dy - y. Of course, this is just f(y)=(1/2)y^2-y which is minimized at y=1, but this is just a minimal ex…

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