# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=509

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**Page:** 510

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## [Best way to store data for GPU use](https://discourse.julialang.org/t/best-way-to-store-data-for-gpu-use/20792)

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**Author:** [@MrRobot](https://discourse.julialang.org/u/MrRobot)\
**Replies:** 7\
**Last updated:** [February 16, 2019, 5:27pm UTC](https://discourse.julialang.org/t/best-way-to-store-data-for-gpu-use/20792 "2019-02-16T17:27:14Z")

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Hello, I am writing code in Julia for molecular simulation. Currently it is only for CPU’s, but I would like to convert it to GPU’s once I have it running and tested. I am forever in a quandary about how to store data (…

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## [writing in excel](https://discourse.julialang.org/t/writing-in-excel/9577)

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**Author:** [@razieh95](https://discourse.julialang.org/u/razieh95)\
**Replies:** 3\
**Last updated:** [February 16, 2019, 4:56pm UTC](https://discourse.julialang.org/t/writing-in-excel/9577 "2019-02-16T16:56:53Z")

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hi. How write value variables in different excel sheets?

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## [Sensitivity analysis in optimization](https://discourse.julialang.org/t/sensitivity-analysis-in-optimization/20833)

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**Author:** [@rev](https://discourse.julialang.org/u/rev)\
**Replies:** 2\
**Last updated:** [February 15, 2019, 9:00pm UTC](https://discourse.julialang.org/t/sensitivity-analysis-in-optimization/20833 "2019-02-15T21:00:33Z")

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Hello All, New to Optimization & JuMP. Trying to do sensitivity analysis for this example, and wondering how to get reduced costs, objective coefficients, allowable increase/decrease, shadow prices, and final values for…

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## [Counterfactual Regret Minimization](https://discourse.julialang.org/t/counterfactual-regret-minimization/19543)

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**Author:** [@ajkeith](https://discourse.julialang.org/u/ajkeith)\
**Replies:** 1\
**Last updated:** [February 15, 2019, 8:52pm UTC](https://discourse.julialang.org/t/counterfactual-regret-minimization/19543 "2019-02-15T20:52:11Z")

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Is anyone aware of a Julia implementation of Counterfactual Regret Minimization (CFR)? I found a python implementation but I haven’t been able to find anything in Julia. I’m thinking about writing a Julia implementation…

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## [Function values under the cursor](https://discourse.julialang.org/t/function-values-under-the-cursor/3469)

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**Author:** [@Tulio\_Valentim](https://discourse.julialang.org/u/Tulio_Valentim)\
**Replies:** 4\
**Last updated:** [February 14, 2019, 3:00pm UTC](https://discourse.julialang.org/t/function-values-under-the-cursor/3469 "2019-02-14T15:00:42Z")

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Hi, someone could help me to plot a graph that show the function value under the cursor? For example in the image below if the black point is cursor it will show (-0.5,2) Tks

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## [Parameter Estimate Problem](https://discourse.julialang.org/t/parameter-estimate-problem/20695)

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**Author:** [@hzgzh](https://discourse.julialang.org/u/hzgzh)\
**Replies:** 6\
**Last updated:** [February 14, 2019, 7:37am UTC](https://discourse.julialang.org/t/parameter-estimate-problem/20695 "2019-02-14T07:37:53Z")

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I find the IDA() can’t converge,the program keeping runing ,can’t not stop,how to select DAE algorithm to solve the prob. using Plots,DifferentialEquations,SmoothingSplines,Optim,Sundials using DiffEqParamEstim t=\[ 0, …

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## [User-defined outputs in DifferentialEquations](https://discourse.julialang.org/t/user-defined-outputs-in-differentialequations/20754)

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**Author:** [@asprionj](https://discourse.julialang.org/u/asprionj)\
**Replies:** 3\
**Last updated:** [February 13, 2019, 4:34pm UTC](https://discourse.julialang.org/t/user-defined-outputs-in-differentialequations/20754 "2019-02-13T16:34:54Z")

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Hi, is there a possibility to specify outputs that are recorded along the state variables when running a simulation in DifferentialEquations? I could not find anything relating to this in the documentation… Of course, I…

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## [Functions in @distributed for do not work](https://discourse.julialang.org/t/functions-in-distributed-for-do-not-work/20737)

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**Author:** [@MMalakhov](https://discourse.julialang.org/u/MMalakhov)\
**Replies:** 3\
**Last updated:** [February 13, 2019, 10:04am UTC](https://discourse.julialang.org/t/functions-in-distributed-for-do-not-work/20737 "2019-02-13T10:04:21Z")

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Hello! I use Julia 1.0.2 on Atom. I’m trying to parallel my loop and there is a problem which I don’t understand. Parallel loops work great without functions inside. Also program work great on 1 worker with functions. …

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## [Query.jl: How can I write type-preserving methods for iterable tables](https://discourse.julialang.org/t/query-jl-how-can-i-write-type-preserving-methods-for-iterable-tables/19956)

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**Author:** [@ablaom](https://discourse.julialang.org/u/ablaom)\
**Replies:** 2\
**Last updated:** [February 13, 2019, 5:46am UTC](https://discourse.julialang.org/t/query-jl-how-can-i-write-type-preserving-methods-for-iterable-tables/19956 "2019-02-13T05:46:16Z")

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In MLJ.jl, we are trying to write a data-agnostic machine-learning framework and are presently trying to make this work using Query, to which I am new. We would like to write methods that take an iterable table as input…

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## [JuliaDB cross reference](https://discourse.julialang.org/t/juliadb-cross-reference/20705)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 3\
**Last updated:** [February 12, 2019, 8:00pm UTC](https://discourse.julialang.org/t/juliadb-cross-reference/20705 "2019-02-12T20:00:52Z")

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Disclaimer: I do not know any SQL. JuliaDB seems really straightforward so I’m trying it instead of some SQLish solution (although I suspect that’s what I should be using). I have a few tables (currently saved as .csv f…

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## [Sub set selection and column generation](https://discourse.julialang.org/t/sub-set-selection-and-column-generation/20716)

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**Author:** [@ndinsmore](https://discourse.julialang.org/u/ndinsmore)\
**Replies:** 0\
**Last updated:** [February 12, 2019, 5:55pm UTC](https://discourse.julialang.org/t/sub-set-selection-and-column-generation/20716 "2019-02-12T17:55:23Z")

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Before I ask my question let me give you an overview of the basic problem I am trying to solve: Given: 1.) a set of 2000+ nodes + node A & B 2.) With 20+ different connected graphs made up of a sub set of the given s…

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## [Problem defining a Straight Through Estimator gradient](https://discourse.julialang.org/t/problem-defining-a-straight-through-estimator-gradient/20698)

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**Author:** [@velix](https://discourse.julialang.org/u/velix)\
**Replies:** 0\
**Last updated:** [February 12, 2019, 11:31am UTC](https://discourse.julialang.org/t/problem-defining-a-straight-through-estimator-gradient/20698 "2019-02-12T11:31:00Z")

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Hi all, I am trying to define a custom STE gradient in Flux. The activation function is the sign function, and its gradient should just be the incoming gradient as is, iff its absolute value is \<= 1, or cancelled other…

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## [Using RemoteChannels in a Publisher/Subscriber Model](https://discourse.julialang.org/t/using-remotechannels-in-a-publisher-subscriber-model/20523)

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**Author:** [@colinxs](https://discourse.julialang.org/u/colinxs)\
**Replies:** 2\
**Last updated:** [February 12, 2019, 10:52am UTC](https://discourse.julialang.org/t/using-remotechannels-in-a-publisher-subscriber-model/20523 "2019-02-12T10:52:31Z")

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Hello all! I’m interested in leveraging Julia’s built-in RemoteChannels to replicate some of the functionality that ROS (http://www.ros.org/) provides. Unfortunately I’m running into some issues with calling put! on a R…

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## [Understanding GRU forward pass as implemented in Knet](https://discourse.julialang.org/t/understanding-gru-forward-pass-as-implemented-in-knet/20639)

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**Author:** [@Christian\_Dengler](https://discourse.julialang.org/u/Christian_Dengler)\
**Replies:** 1\
**Last updated:** [February 12, 2019, 5:00am UTC](https://discourse.julialang.org/t/understanding-gru-forward-pass-as-implemented-in-knet/20639 "2019-02-12T05:00:06Z")

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Hello all, I tried to reimplement the simple forward pass of a GRU layer in order to be able to evaluate the RNN in other languages after training in Julia. So far with no luck, and Im starting to be out of ideas. Is th…

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## [Please can you explain the use of get! and IdDict in optimisers.jl](https://discourse.julialang.org/t/please-can-you-explain-the-use-of-get-and-iddict-in-optimisers-jl/20685)

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**Author:** [@murphyk](https://discourse.julialang.org/u/murphyk)\
**Replies:** 5\
**Last updated:** [February 12, 2019, 12:51am UTC](https://discourse.julialang.org/t/please-can-you-explain-the-use-of-get-and-iddict-in-optimisers-jl/20685 "2019-02-12T00:51:24Z")

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I’m trying to understand the optimization code for momentum which reads function apply!(o::Momentum, x, Δ) η, ρ = o.eta, o.rho v = get!(o.velocity, x, zero(x))::typeof(x) @. v = ρ \* v - η \* Δ @. Δ = -v end I do…

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## [Uncertainties in DiffEqFlux.jl](https://discourse.julialang.org/t/uncertainties-in-diffeqflux-jl/20660)

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**Author:** [@spinkney](https://discourse.julialang.org/u/spinkney)\
**Replies:** 2\
**Last updated:** [February 11, 2019, 9:40pm UTC](https://discourse.julialang.org/t/uncertainties-in-diffeqflux-jl/20660 "2019-02-11T21:40:51Z")

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I watched the JuliaCon 2018 | PuMaS.jl: Pharmaceutical Modeling and Simulation Engine given by @ChrisRackauckas and saw the part about propagation of parameter uncertainties around 21:47. A (possibly) quick question reg…

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## [Electro and magneto statics](https://discourse.julialang.org/t/electro-and-magneto-statics/20634)

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**Author:** [@Lee\_Streeter](https://discourse.julialang.org/u/Lee_Streeter)\
**Replies:** 6\
**Last updated:** [February 11, 2019, 8:35pm UTC](https://discourse.julialang.org/t/electro-and-magneto-statics/20634 "2019-02-11T20:35:21Z")

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I’ve been hunting for a package for electro and magneto static modelling. The best I can find are a few FEM packages that have not had recent updates for over a year (according to github). Right now I’m looking into Dif…

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## [Automatic Differentiation](https://discourse.julialang.org/t/automatic-differentiation/17472)

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**Author:** [@kkmann](https://discourse.julialang.org/u/kkmann)\
**Replies:** 11\
**Last updated:** [February 11, 2019, 2:19pm UTC](https://discourse.julialang.org/t/automatic-differentiation/17472 "2019-02-11T14:19:18Z")

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Hey, I am still having a bit of a hard time figuring out what flux.jl actually does. One important aspect seems to be making gradients available automatically via tracking. How does that differ from the approach in Forw…

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## [Applying \`quantile\` to \`AbstractArray\`s](https://discourse.julialang.org/t/applying-quantile-to-abstractarray-s/20619)

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**Author:** [@heliosdrm](https://discourse.julialang.org/u/heliosdrm)\
**Replies:** 1\
**Last updated:** [February 10, 2019, 12:11am UTC](https://discourse.julialang.org/t/applying-quantile-to-abstractarray-s/20619 "2019-02-10T00:11:35Z")

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The docstring of quantile in the Statistics module says: quantile(itr, p; sorted=false) Compute the quantile(s) of a collection itr at a specified probability or vector or tuple of probabilities p on the interval \[0,…

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## [New blog post on banded matrices and ordinary differential equations using BandedMatrices.jl](https://discourse.julialang.org/t/new-blog-post-on-banded-matrices-and-ordinary-differential-equations-using-bandedmatrices-jl/18564)

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**Author:** [@dlfivefifty](https://discourse.julialang.org/u/dlfivefifty)\
**Replies:** 31\
**Last updated:** [February 9, 2019, 7:12am UTC](https://discourse.julialang.org/t/new-blog-post-on-banded-matrices-and-ordinary-differential-equations-using-bandedmatrices-jl/18564 "2019-02-09T07:12:55Z")

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I just posted my first blog post, on using BandedMatrices.jl to solve ordinary differential equations via finite differences / spectral methods: Banded matrices and ordinary differential equations This is first of a ser…

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## [GPU Map without reduction on multiple arrays indices](https://discourse.julialang.org/t/gpu-map-without-reduction-on-multiple-arrays-indices/20565)

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**Author:** [@mleprovost](https://discourse.julialang.org/u/mleprovost)\
**Replies:** 1\
**Last updated:** [February 8, 2019, 7:20am UTC](https://discourse.julialang.org/t/gpu-map-without-reduction-on-multiple-arrays-indices/20565 "2019-02-08T07:20:11Z")

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Hello, I would like to compute a multi-dimensional array (4-D) A of a 2 components function f on a large multi-dimensional domain (X,Y,T) with GPU. So A will have size: 2, NX, NY, NT. X, Y and T are 1D arrays I tried …

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## [Run external commands in parallel](https://discourse.julialang.org/t/run-external-commands-in-parallel/20268)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 10\
**Last updated:** [February 7, 2019, 6:59pm UTC](https://discourse.julialang.org/t/run-external-commands-in-parallel/20268 "2019-02-07T18:59:22Z")

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I have a computation for which the time-consuming part boils down to calling an external program, in particular with read(cmd, String) in parallel for 1-5 values of cmd. Should I just construct the commands, and use pma…

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## [StackOverflowError with julia v1.1 similar to previous bug v0.7](https://discourse.julialang.org/t/stackoverflowerror-with-julia-v1-1-similar-to-previous-bug-v0-7/20531)

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**Author:** [@tlagos](https://discourse.julialang.org/u/tlagos)\
**Replies:** 5\
**Last updated:** [February 7, 2019, 5:26pm UTC](https://discourse.julialang.org/t/stackoverflowerror-with-julia-v1-1-similar-to-previous-bug-v0-7/20531 "2019-02-07T17:26:42Z")

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Hi everyone, I’ve been dealing with a similar error that this one. The output is the following: ERROR: LoadError: StackOverflowError: Stacktrace: \[1\] (::Interpolations.GriddedInterpolation{Float64,1,Float64,Gridded{Li…

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## [DifferentialEquations.jl: complex-value matrix equations without in-place update](https://discourse.julialang.org/t/differentialequations-jl-complex-value-matrix-equations-without-in-place-update/20110)

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**Author:** [@Egwene\_al\_Vere](https://discourse.julialang.org/u/Egwene_al_Vere)\
**Replies:** 1\
**Last updated:** [February 7, 2019, 2:49pm UTC](https://discourse.julialang.org/t/differentialequations-jl-complex-value-matrix-equations-without-in-place-update/20110 "2019-02-07T14:49:30Z")

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To solve a stiff complex-value matrix equation, I’m using the Rosenbrock23() solver. As a minimum working example, (may not be stiff, just to illustrate the error I got) With in-place du, (function taking 4 arguments: d…

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## [How to design distributed (CPU/GPU) reinforcement learning methods?](https://discourse.julialang.org/t/how-to-design-distributed-cpu-gpu-reinforcement-learning-methods/20539)

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**Author:** [@jbrea](https://discourse.julialang.org/u/jbrea)\
**Replies:** 0\
**Last updated:** [February 7, 2019, 10:17am UTC](https://discourse.julialang.org/t/how-to-design-distributed-cpu-gpu-reinforcement-learning-methods/20539 "2019-02-07T10:17:55Z")

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Question to the experts on distributed computing: How should we design distributed reinforcement learning methods in julia? Ray has a nice approach with different optimizers for methods that move around gradients or ba…

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## [\[ANN\] AstroTime.jl: Astronomical time keeping in Julia](https://discourse.julialang.org/t/ann-astrotime-jl-astronomical-time-keeping-in-julia/20496)

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**Author:** [@helgee](https://discourse.julialang.org/u/helgee)\
**Replies:** 1\
**Last updated:** [February 7, 2019, 12:24am UTC](https://discourse.julialang.org/t/ann-astrotime-jl-astronomical-time-keeping-in-julia/20496 "2019-02-07T00:24:55Z")

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Hi folks! I have finally published the first version of AstroTime.jl :tada: This one has been an almost astronomically long time in the making (sorry, could not resist :smile:). The first commit (when the code was stil…

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## [Pipeline : from raw data to fitted model?](https://discourse.julialang.org/t/pipeline-from-raw-data-to-fitted-model/20477)

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**Author:** [@kirtsar](https://discourse.julialang.org/u/kirtsar)\
**Replies:** 6\
**Last updated:** [February 6, 2019, 10:22pm UTC](https://discourse.julialang.org/t/pipeline-from-raw-data-to-fitted-model/20477 "2019-02-06T22:22:31Z")

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Hello everyone! I’m a novice in machine learning domain. I’m interested in basic ML pipeline from raw dataframe with missing values and so on to the trained model. Is there any unified process of pipelining such method…

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## [How to fit a GLM to all (unnamed) features of arbitrary design matrix?](https://discourse.julialang.org/t/how-to-fit-a-glm-to-all-unnamed-features-of-arbitrary-design-matrix/20490)

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**Author:** [@murphyk](https://discourse.julialang.org/u/murphyk)\
**Replies:** 2\
**Last updated:** [February 6, 2019, 9:18pm UTC](https://discourse.julialang.org/t/how-to-fit-a-glm-to-all-unnamed-features-of-arbitrary-design-matrix/20490 "2019-02-06T21:18:13Z")

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I want to call the GLM.jl library as a blackbox, which means I want to use a formula of the form “y ~ .”, where y is the target column of my dataframe, and . is all the other features. Specifically, what I would like to…

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## [What other language allows you to do Rational matrix inversion?](https://discourse.julialang.org/t/what-other-language-allows-you-to-do-rational-matrix-inversion/20340)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 15\
**Last updated:** [February 6, 2019, 1:20am UTC](https://discourse.julialang.org/t/what-other-language-allows-you-to-do-rational-matrix-inversion/20340 "2019-02-06T01:20:37Z")

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I was just doing some Hackerrank for fun, in particular this one. Basically, you can describe the problem as a sequence of recurrence relations, and they told you that the solution is in the form of a rational number. S…

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## [Optim - provide gradient with fixed parameters](https://discourse.julialang.org/t/optim-provide-gradient-with-fixed-parameters/20181)

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**Author:** [@itzui](https://discourse.julialang.org/u/itzui)\
**Replies:** 10\
**Last updated:** [February 5, 2019, 8:10pm UTC](https://discourse.julialang.org/t/optim-provide-gradient-with-fixed-parameters/20181 "2019-02-05T20:10:12Z")

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I’m using Optim and the BFGS algarithm in order to minimize a function. In order to speed up the minimization I want to provide the gradient of the objective function. However both, the objective function as well as the …

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