# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=289

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**Page:** 290

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## [How to use string in @nlexpression](https://discourse.julialang.org/t/how-to-use-string-in-nlexpression/79374)

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**Author:** [@manoj.centura](https://discourse.julialang.org/u/manoj.centura)\
**Replies:** 1\
**Last updated:** [April 12, 2022, 6:47pm UTC](https://discourse.julialang.org/t/how-to-use-string-in-nlexpression/79374 "2022-04-12T18:47:59Z")

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Hi All, i want to create @NL expreesion on fly in JuMP. I am getting the below error. model = Model() @variable(model, x\[1:3\]) @constraint(model, c2, x\[1\] + 2 \* x\[3\] \>= 2) @constraint(model, c4, 4 \<= 2 \* x\[2\] \<= 5) …

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## [Help me beat my pythonist friend's code. Speeding up data reading with simple reduction from NetCDF file](https://discourse.julialang.org/t/help-me-beat-my-pythonist-friends-code-speeding-up-data-reading-with-simple-reduction-from-netcdf-file/76457)

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**Author:** [@aramirezreyes](https://discourse.julialang.org/u/aramirezreyes)\
**Replies:** 57\
**Last updated:** [April 12, 2022, 4:35pm UTC](https://discourse.julialang.org/t/help-me-beat-my-pythonist-friends-code-speeding-up-data-reading-with-simple-reduction-from-netcdf-file/76457 "2022-04-12T16:35:49Z")

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I work with atmospheric simulations and I use NetCDF files of the order of 80GB to 1TB. I am always jelous at my friend from the office (@lsterzinger) that does everything super fast in his python with xarray, zarr, da…

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## [Working around current MethodOfLines.jl known limitations](https://discourse.julialang.org/t/working-around-current-methodoflines-jl-known-limitations/79346)

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**Author:** [@jenrei](https://discourse.julialang.org/u/jenrei)\
**Replies:** 4\
**Last updated:** [April 12, 2022, 4:25pm UTC](https://discourse.julialang.org/t/working-around-current-methodoflines-jl-known-limitations/79346 "2022-04-12T16:25:58Z")

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Hi, I’m trying to solve the energy/heat equation with temperature dependent material properties (density, enthalpy and thermal conductivity). Therefore I’m running in the issues that are mentioned as (current) known limi…

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## [Mapping Hwloc logical index to OS index](https://discourse.julialang.org/t/mapping-hwloc-logical-index-to-os-index/79377)

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**Author:** [@Gregstrq](https://discourse.julialang.org/u/Gregstrq)\
**Replies:** 5\
**Last updated:** [April 12, 2022, 3:12pm UTC](https://discourse.julialang.org/t/mapping-hwloc-logical-index-to-os-index/79377 "2022-04-12T15:12:29Z")

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The docs for Hwloc library state that the logical indices of Processor units used by Hwloc are not the same as the indices used by OS. How does one map Hwloc logical indices to OS indices? Is this functionality exposed…

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## [Struggling to get scipy.newton performance using NonlinearSolve.jl](https://discourse.julialang.org/t/struggling-to-get-scipy-newton-performance-using-nonlinearsolve-jl/79369)

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**Author:** [@deserted\_eagle](https://discourse.julialang.org/u/deserted_eagle)\
**Replies:** 4\
**Last updated:** [April 12, 2022, 3:06pm UTC](https://discourse.julialang.org/t/struggling-to-get-scipy-newton-performance-using-nonlinearsolve-jl/79369 "2022-04-12T15:06:38Z")

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Hi everyone! I’m relatively new to Julia (1.7.2), coming from a Matlab and Python background. I really enjoy the language, but I also struggle sometimes in cases where in Matlab / numpy I would simply use vectorization a…

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## [Using juniper with ipopt and cbc in julia.1.6](https://discourse.julialang.org/t/using-juniper-with-ipopt-and-cbc-in-julia-1-6/78394)

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**Author:** [@manoj.centura](https://discourse.julialang.org/u/manoj.centura)\
**Replies:** 2\
**Last updated:** [April 12, 2022, 1:20pm UTC](https://discourse.julialang.org/t/using-juniper-with-ipopt-and-cbc-in-julia-1-6/78394 "2022-04-12T13:20:43Z")

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Subject to maximumqty == 111371.4 x\[1,1,1,1,1\] + x\[2,1,1,1,1\] + x\[3,1,1,1,1\] + x\[4,1,1,1,1\] + x\[5,1,1,1,1\] + x\[1,1,1,1,2\] + x\[2,1,1,1,2\] + x\[3,1,1,1,2\] + x\[4,1,1,1,2\] + x\[5,1,1,1,2\] - MaxWt == 0.0 x\[1,1,1,1,1\] - 56014…

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## [HTTP server with parallelism](https://discourse.julialang.org/t/http-server-with-parallelism/79370)

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**Author:** [@xor0110](https://discourse.julialang.org/u/xor0110)\
**Replies:** 1\
**Last updated:** [April 12, 2022, 9:34am UTC](https://discourse.julialang.org/t/http-server-with-parallelism/79370 "2022-04-12T09:34:20Z")

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This question relates a bit to HTTP.jl doesn't seem to be good at handling over 1k concurrent requests, in comparison to an alternative in Python?: I’m interested in creating a HTTP server that executes CPU-heavy tasks.…

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## [Suggestions on model and solvers](https://discourse.julialang.org/t/suggestions-on-model-and-solvers/79345)

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**Author:** [@Patrik\_Waldmann](https://discourse.julialang.org/u/Patrik_Waldmann)\
**Replies:** 3\
**Last updated:** [April 12, 2022, 4:47am UTC](https://discourse.julialang.org/t/suggestions-on-model-and-solvers/79345 "2022-04-12T04:47:36Z")

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I would be happy for suggestions on how and where to implement the model for the data below (the plan is to extend to a much larger data set later so speed is of interest): #Toy data A = \[1.0000 0 0.5000 0.5000 0.4714 0…

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## [Intersection of two rotated rectangles?](https://discourse.julialang.org/t/intersection-of-two-rotated-rectangles/79312)

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**Author:** [@vshesh](https://discourse.julialang.org/u/vshesh)\
**Replies:** 6\
**Last updated:** [April 12, 2022, 12:20am UTC](https://discourse.julialang.org/t/intersection-of-two-rotated-rectangles/79312 "2022-04-12T00:20:26Z")

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Is there a julia implemented version of deciding whether two rects intersect? rects are rotated about their top left corner, specified as \[x, y, width, height, angle\] so for example: \> collision(\[0,0,100,100,0\], \[40,4…

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## [Pre-allocated eigen value decomposition](https://discourse.julialang.org/t/pre-allocated-eigen-value-decomposition/79358)

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**Author:** [@jinml](https://discourse.julialang.org/u/jinml)\
**Replies:** 2\
**Last updated:** [April 11, 2022, 10:07pm UTC](https://discourse.julialang.org/t/pre-allocated-eigen-value-decomposition/79358 "2022-04-11T22:07:07Z")

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Is there a way to pre-allocate an array to hold the returned eigenvalues and vectors from eigen or eigen! ? Currently both functions return a factorization which does not seem to allow a pre-allocation. The following cod…

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## [Setting nonlinear objectives with JuMP](https://discourse.julialang.org/t/setting-nonlinear-objectives-with-jump/79343)

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**Author:** [@Hans\_W\_Borchers](https://discourse.julialang.org/u/Hans_W_Borchers)\
**Replies:** 4\
**Last updated:** [April 11, 2022, 7:59pm UTC](https://discourse.julialang.org/t/setting-nonlinear-objectives-with-jump/79343 "2022-04-11T19:59:18Z")

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Dear All, one year ago I have written a small note on how to use Julia from R through the ‘JuliaCall’ package. I wanted to update this page and encountered some problems with Julia’s JuMP package. See Notes on JuliaCall…

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## [Simple Flux LSTM for Time Series](https://discourse.julialang.org/t/simple-flux-lstm-for-time-series/35494)

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**Author:** [@compleat](https://discourse.julialang.org/u/compleat)\
**Replies:** 62\
**Last updated:** [April 11, 2022, 7:02pm UTC](https://discourse.julialang.org/t/simple-flux-lstm-for-time-series/35494 "2022-04-11T19:02:45Z")

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Hi, I have been trying for a long time to get Flux working for a basic time series. I think if I can get a really simple example working, I would be able to go from there, but when I try to do the ‘obvious’ thing, it fa…

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## [Compare 2 data sets - similar to SAS proc compare](https://discourse.julialang.org/t/compare-2-data-sets-similar-to-sas-proc-compare/79215)

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**Author:** [@ab2z](https://discourse.julialang.org/u/ab2z)\
**Replies:** 4\
**Last updated:** [April 11, 2022, 6:02pm UTC](https://discourse.julialang.org/t/compare-2-data-sets-similar-to-sas-proc-compare/79215 "2022-04-11T18:02:38Z")

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Question: what is the best command for comparing 2 datasets - something like proc compare in SAS ? I could not edit this Comparison 2 data sets , So I decide to open this new topic. I have the following example old=Da…

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## [Discrepency related to using \`\`\`lyapunovspectrum\`\`\` from DynamicalSystems.jl package](https://discourse.julialang.org/t/discrepency-related-to-using-lyapunovspectrum-from-dynamicalsystems-jl-package/75453)

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**Author:** [@pafloxy](https://discourse.julialang.org/u/pafloxy)\
**Replies:** 9\
**Last updated:** [April 11, 2022, 2:53pm UTC](https://discourse.julialang.org/t/discrepency-related-to-using-lyapunovspectrum-from-dynamicalsystems-jl-package/75453 "2022-04-11T14:53:07Z")

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Hi! I was trying out the lyapunovspectrum function in Julia, for a few standard dynamical systems like Rossler. I compared the results obtained by using lyapunovspectrum to the spectrum obtained by manually initiating a…

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## [\`@variables\` and \`@parameters\` macros not working on arrays](https://discourse.julialang.org/t/variables-and-parameters-macros-not-working-on-arrays/79252)

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**Author:** [@markjholmes](https://discourse.julialang.org/u/markjholmes)\
**Replies:** 14\
**Last updated:** [April 11, 2022, 1:51pm UTC](https://discourse.julialang.org/t/variables-and-parameters-macros-not-working-on-arrays/79252 "2022-04-11T13:51:30Z")

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I have Julia installed on two different computers and the code executes differently on each one despite having the same versions of VSCode, Julia, and installed packages (everything is the most recent release version). T…

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## [Request for review basic introductory pages on ML, Perceptron, Neural Networks](https://discourse.julialang.org/t/request-for-review-basic-introductory-pages-on-ml-perceptron-neural-networks/79341)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 0\
**Last updated:** [April 11, 2022, 11:53am UTC](https://discourse.julialang.org/t/request-for-review-basic-introductory-pages-on-ml-perceptron-neural-networks/79341 "2022-04-11T11:53:24Z")

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Hello, I have a couple of pages dealing with: General ML concepts and perceptron algorithm Neural network architectures These two small “pages” are targeted to non-cs / non-math students that know nothing of ML, with …

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## [JuMP docs on SDP replace \`logdet\` with \`tr\`—is this correct?](https://discourse.julialang.org/t/jump-docs-on-sdp-replace-logdet-with-tr-is-this-correct/79324)

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**Author:** [@maxkapur](https://discourse.julialang.org/u/maxkapur)\
**Replies:** 4\
**Last updated:** [April 11, 2022, 6:28am UTC](https://discourse.julialang.org/t/jump-docs-on-sdp-replace-logdet-with-tr-is-this-correct/79324 "2022-04-11T06:28:49Z")

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The JuMP documentation gives, as an example of a semidefinite program, the problem of finding the minimum-volume ellipse that contains a given list of ellipses centered at the origin: minimize trace(WX) subject to X…

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## [StochasticPrograms.jl - DIfficulties with vector @uncertain inputs](https://discourse.julialang.org/t/stochasticprograms-jl-difficulties-with-vector-uncertain-inputs/45957)

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**Author:** [@elalaouifaris](https://discourse.julialang.org/u/elalaouifaris)\
**Replies:** 10\
**Last updated:** [April 10, 2022, 4:43pm UTC](https://discourse.julialang.org/t/stochasticprograms-jl-difficulties-with-vector-uncertain-inputs/45957 "2022-04-10T16:43:36Z")

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Hi, I’m testing the StochasticPrograms.jl package (Awesome work by the way!) on a simple renewables energy sizing use case. I have difficulty figuring out how to use uncertain parameters in the 2nd stage with array inpu…

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## [The purpose of ThreadingUtilities.jl and Polyester.jl](https://discourse.julialang.org/t/the-purpose-of-threadingutilities-jl-and-polyester-jl/79226)

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**Author:** [@Gregstrq](https://discourse.julialang.org/u/Gregstrq)\
**Replies:** 9\
**Last updated:** [April 10, 2022, 2:12pm UTC](https://discourse.julialang.org/t/the-purpose-of-threadingutilities-jl-and-polyester-jl/79226 "2022-04-10T14:12:34Z")

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As far as I understand, both ThreadingUtilities.jl and Polyster.jl provide the threads with low overhead. Could someone (@Elrod) elaborate the precise difference between the packages and when one should be preferred ove…

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## [Makie rotate colorbar label](https://discourse.julialang.org/t/makie-rotate-colorbar-label/79263)

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**Author:** [@jewh](https://discourse.julialang.org/u/jewh)\
**Replies:** 5\
**Last updated:** [April 10, 2022, 12:44pm UTC](https://discourse.julialang.org/t/makie-rotate-colorbar-label/79263 "2022-04-10T12:44:41Z")

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How do I rotate the label on the colorbar in Makie? MWE: using CairoMakie M = rand(10, 10) fig = CairoMakie.Figure() ax = Axis(fig\[1,1\]) cplot = CairoMakie.contourf!(fig\[1,1\], 1:10, 1:10, M) Colorbar(fig\[1,2\], cplot, …

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## [CairoMakie contourf set colour limits](https://discourse.julialang.org/t/cairomakie-contourf-set-colour-limits/79261)

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**Author:** [@jewh](https://discourse.julialang.org/u/jewh)\
**Replies:** 13\
**Last updated:** [April 10, 2022, 11:12am UTC](https://discourse.julialang.org/t/cairomakie-contourf-set-colour-limits/79261 "2022-04-10T11:12:16Z")

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How do I change the limits for my colour scale in a CairoMakie contourf plot? For instance say I want to plot my data on a contour plot, with a colour bar: using CairoMakie M = rand(10, 10) / 10. # get data ∈ \[0, 1\] a…

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## [Using spectral methods and optimization to find period of a set of nonlinear autonomous differential equations](https://discourse.julialang.org/t/using-spectral-methods-and-optimization-to-find-period-of-a-set-of-nonlinear-autonomous-differential-equations/79293)

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**Author:** [@Gummala\_Navneeth](https://discourse.julialang.org/u/Gummala_Navneeth)\
**Replies:** 0\
**Last updated:** [April 10, 2022, 10:48am UTC](https://discourse.julialang.org/t/using-spectral-methods-and-optimization-to-find-period-of-a-set-of-nonlinear-autonomous-differential-equations/79293 "2022-04-10T10:48:07Z")

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hi all, I’m very new to Julia. I’m following these lectures to solve optimization problem. I will be providing a toy problem (2 DoF) which mimics my actual problem (12 DoF). I have a set of nonlinear non-autonomous dif…

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## [How to fit a FitzHugh-Nagumo model with DiffEqFlux.jl?](https://discourse.julialang.org/t/how-to-fit-a-fitzhugh-nagumo-model-with-diffeqflux-jl/79194)

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**Author:** [@PikaPei](https://discourse.julialang.org/u/PikaPei)\
**Replies:** 3\
**Last updated:** [April 10, 2022, 10:14am UTC](https://discourse.julialang.org/t/how-to-fit-a-fitzhugh-nagumo-model-with-diffeqflux-jl/79194 "2022-04-10T10:14:45Z")

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I try to apply the DiffEqFlux to the FitzHugh-Nagumo model, an excitable neuron model. Basically, I only replace the differential equations in this tutorial (Neural Ordinary Differential Equations with sciml\_train) with…

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## [Linear algebra of sparse matrices on GPU](https://discourse.julialang.org/t/linear-algebra-of-sparse-matrices-on-gpu/79287)

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**Author:** [@Vahid\_Hosseinzadeh](https://discourse.julialang.org/u/Vahid_Hosseinzadeh)\
**Replies:** 0\
**Last updated:** [April 10, 2022, 7:41am UTC](https://discourse.julialang.org/t/linear-algebra-of-sparse-matrices-on-gpu/79287 "2022-04-10T07:41:43Z")

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Hello everyone, I have a code with some computations in LinearAlgebra using SparseArrays. How can I use that to be performed on GPU? Can I use Cuda.jl? what functions are available in linear algebra? In my case, I need…

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## [Errors with Flux RNN set](https://discourse.julialang.org/t/errors-with-flux-rnn-set/79272)

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**Author:** [@stmorg](https://discourse.julialang.org/u/stmorg)\
**Replies:** 1\
**Last updated:** [April 9, 2022, 9:42pm UTC](https://discourse.julialang.org/t/errors-with-flux-rnn-set/79272 "2022-04-09T21:42:08Z")

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Hi everyone, I’m currently working on a final project that involves developing an RNN to represent a parameterized dynamic model. I have been able to do this fairly easily with a feedforward ANN in Flux but I have had ma…

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## [PGFPlotsX: annotate outside plot area](https://discourse.julialang.org/t/pgfplotsx-annotate-outside-plot-area/58357)

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**Author:** [@lmiq](https://discourse.julialang.org/u/lmiq)\
**Replies:** 5\
**Last updated:** [April 9, 2022, 10:47am UTC](https://discourse.julialang.org/t/pgfplotsx-annotate-outside-plot-area/58357 "2022-04-09T10:47:52Z")

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How can I put annotations outside the plotting area of a plot in PGFPlotsX? Example: using Plots pgfplotsx(grid=:false) scatter(rand(5),rand(5),xlim=\[0,1\],ylim=\[0,1\]) annotate!(0.5,0.5,text("inside plot")) annotate!(0,…

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## [Callback jump MOI interface lazy constraints are not cutting the solution properly](https://discourse.julialang.org/t/callback-jump-moi-interface-lazy-constraints-are-not-cutting-the-solution-properly/79227)

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**Author:** [@afazevedo](https://discourse.julialang.org/u/afazevedo)\
**Replies:** 1\
**Last updated:** [April 8, 2022, 10:50pm UTC](https://discourse.julialang.org/t/callback-jump-moi-interface-lazy-constraints-are-not-cutting-the-solution-properly/79227 "2022-04-08T22:50:50Z")

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Hey there, can anyone please help me? I am trying to solve a combinatorial optimization problem through lazy constraints using Gurobi as Solver. Bellow a code of my presets and variables: model = Model(Gurobi.Optimizer…

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## [Primer feasibility question - modelling soft tissue behavior using ML](https://discourse.julialang.org/t/primer-feasibility-question-modelling-soft-tissue-behavior-using-ml/76175)

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**Author:** [@davide445](https://discourse.julialang.org/u/davide445)\
**Replies:** 13\
**Last updated:** [April 8, 2022, 8:41pm UTC](https://discourse.julialang.org/t/primer-feasibility-question-modelling-soft-tissue-behavior-using-ml/76175 "2022-04-08T20:41:33Z")

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Get interested in Julia since seems crossing many of the themes i’m touching lately: HPC, biophysics, GPGPU, ML, with the goal to create interactive systems. Not a coder, I’m a solution designer that is deepening on dif…

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## [Custum DataInspector display-value \[Makie\]](https://discourse.julialang.org/t/custum-datainspector-display-value-makie/79235)

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**Author:** [@TheLateKronos](https://discourse.julialang.org/u/TheLateKronos)\
**Replies:** 1\
**Last updated:** [April 8, 2022, 8:24pm UTC](https://discourse.julialang.org/t/custum-datainspector-display-value-makie/79235 "2022-04-08T20:24:13Z")

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I have a scatterplot, showing the time-evolution of some neural networks (x-axis = time) against performance (y-axis = performance). Each network has an ID. It would be fantastic if I could get the network ID (which I wo…

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## [Iteratively compute eigenvalues of non-Hermitian sparse matrix](https://discourse.julialang.org/t/iteratively-compute-eigenvalues-of-non-hermitian-sparse-matrix/79236)

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**Author:** [@jamblejoe](https://discourse.julialang.org/u/jamblejoe)\
**Replies:** 0\
**Last updated:** [April 8, 2022, 6:58pm UTC](https://discourse.julialang.org/t/iteratively-compute-eigenvalues-of-non-hermitian-sparse-matrix/79236 "2022-04-08T18:58:11Z")

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Let A be a real, non-symmetric, sparse matrix with eigenvalues having real part smaller than or equal to 0. We can assume that if the real part of an eigenvalue λ is 0 then λ=0. The multiplicity of the 0 eigenvalue is gr…

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