# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=544

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**Page:** 545

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## [Using JuMP fails](https://discourse.julialang.org/t/using-jump-fails/9054)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 1\
**Last updated:** [February 14, 2018, 12:59pm UTC](https://discourse.julialang.org/t/using-jump-fails/9054 "2018-02-14T12:59:18Z")

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Hello, after updating my packages I get the following error: julia\> using JuMP INFO: Precompiling module JuMP. WARNING: Module ReverseDiffSparse with uuid 11646900819455 is missing from the cache. This may mean module …

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## [Count number of substrings in dataframe column](https://discourse.julialang.org/t/count-number-of-substrings-in-dataframe-column/9036)

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**Author:** [@jacobcvt12](https://discourse.julialang.org/u/jacobcvt12)\
**Replies:** 8\
**Last updated:** [February 13, 2018, 11:07pm UTC](https://discourse.julialang.org/t/count-number-of-substrings-in-dataframe-column/9036 "2018-02-13T23:07:38Z")

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I have a dataset (read in from a CSV). I’m trying to count how many observations contain a substring (for simplicity, let’s call it “X”). In R, I can do this sum(stringr::str\_count(data$CITY, "X")) \> 0 I’m having troub…

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## [Making a callback event at a single timepoint](https://discourse.julialang.org/t/making-a-callback-event-at-a-single-timepoint/9038)

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**Author:** [@Torkel](https://discourse.julialang.org/u/Torkel)\
**Replies:** 4\
**Last updated:** [February 13, 2018, 4:44pm UTC](https://discourse.julialang.org/t/making-a-callback-event-at-a-single-timepoint/9038 "2018-02-13T16:44:51Z")

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Simple question. At a certain timepoint (e.g. t = 100) I want to make a callback, changing a parameter or variable value. The most intuitive way would be function condition(u,t,integrator) t == 100 end however the…

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## [Events that changes parameter values](https://discourse.julialang.org/t/events-that-changes-parameter-values/9015)

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**Author:** [@Torkel](https://discourse.julialang.org/u/Torkel)\
**Replies:** 4\
**Last updated:** [February 13, 2018, 4:01pm UTC](https://discourse.julialang.org/t/events-that-changes-parameter-values/9015 "2018-02-13T16:01:24Z")

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I am running simulations on chemical reaction systems. Usually for these I have some input signal and I want to investigate what happens to the system when suddenly an input is turned on. Typically I might have a variabl…

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## [Recommended way to save and read DataFrames in JSON format](https://discourse.julialang.org/t/recommended-way-to-save-and-read-dataframes-in-json-format/8990)

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**Author:** [@piever](https://discourse.julialang.org/u/piever)\
**Replies:** 8\
**Last updated:** [February 12, 2018, 6:33pm UTC](https://discourse.julialang.org/t/recommended-way-to-save-and-read-dataframes-in-json-format/8990 "2018-02-12T18:33:24Z")

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I need to save some tabular data in JSON format (from a game engine) to read it in Julia as a DataFrame (or IndexedTable). I’m trying to understand what is the best way to save this kind of data in JSON. The following tw…

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## [Arguments passing behaviour for @spawnat and fetch](https://discourse.julialang.org/t/arguments-passing-behaviour-for-spawnat-and-fetch/9018)

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**Author:** [@Gregstrq](https://discourse.julialang.org/u/Gregstrq)\
**Replies:** 0\
**Last updated:** [February 12, 2018, 5:06pm UTC](https://discourse.julialang.org/t/arguments-passing-behaviour-for-spawnat-and-fetch/9018 "2018-02-12T17:06:17Z")

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I am trying to figure out how data communication between procs is organized, but the docs are a bit vague about this. Do I understand correctly, that any time you do @spawnat worker\_id somefunc(args...), the arguments …

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## [Is there a way that I can attach string labels to integer values in CategoricalArrays?](https://discourse.julialang.org/t/is-there-a-way-that-i-can-attach-string-labels-to-integer-values-in-categoricalarrays/8970)

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**Author:** [@mwsohn](https://discourse.julialang.org/u/mwsohn)\
**Replies:** 9\
**Last updated:** [February 11, 2018, 10:24pm UTC](https://discourse.julialang.org/t/is-there-a-way-that-i-can-attach-string-labels-to-integer-values-in-categoricalarrays/8970 "2018-02-11T22:24:34Z")

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I noticed that CategoricalPool type allows labels for categorical values. I am wondering whether there is a way that I can convert an integer variable to a Categorical Array with string labels corresponding to each integ…

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## [Iterate over all numeric columns in DataFrames](https://discourse.julialang.org/t/iterate-over-all-numeric-columns-in-dataframes/8916)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 21\
**Last updated:** [February 11, 2018, 6:12am UTC](https://discourse.julialang.org/t/iterate-over-all-numeric-columns-in-dataframes/8916 "2018-02-11T06:12:58Z")

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beginner’s questions: how do I iterate over all numeric columns in a DataFrame, e.g., to calculate means or sum-cubed? bonus question: can DataFrames consider NaN to be a missing value for Float32 and Float64, too,…

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## [\`max\` constraints in JuMP](https://discourse.julialang.org/t/max-constraints-in-jump/8983)

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**Author:** [@jacob-roth](https://discourse.julialang.org/u/jacob-roth)\
**Replies:** 5\
**Last updated:** [February 11, 2018, 5:39am UTC](https://discourse.julialang.org/t/max-constraints-in-jump/8983 "2018-02-11T05:39:30Z")

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Similar to this question, how can I formulate a constraint involving max of the form \\sum\_{i=1}^m \[z\_i + t\]\_+ \\leq c where \[x\]\_+ = \\max(x,0), both t,c \\in \\mathbb{R}, and z = My \\in \\mathbb{R}^m for variable y \\in \\mathb…

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## [How do I do a binary classification with GLMnet, or Lasso?](https://discourse.julialang.org/t/how-do-i-do-a-binary-classification-with-glmnet-or-lasso/8933)

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**Author:** [@oxinabox](https://discourse.julialang.org/u/oxinabox)\
**Replies:** 4\
**Last updated:** [February 9, 2018, 3:40pm UTC](https://discourse.julialang.org/t/how-do-i-do-a-binary-classification-with-glmnet-or-lasso/8933 "2018-02-09T15:40:43Z")

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I wanted to include GLMnet and Lasso in http://white.ucc.asn.au/2017/12/18/7-Binary-Classifier-Libraries-in-Julia.html But I outright could not work out how to use them. I feel like they can be used for this, but ma…

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## [Fail Testing Mosek 8 -\> ERROR: LoadError: ReadOnlyMemoryError()](https://discourse.julialang.org/t/fail-testing-mosek-8-error-loaderror-readonlymemoryerror/8891)

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**Author:** [@erikfilias](https://discourse.julialang.org/u/erikfilias)\
**Replies:** 5\
**Last updated:** [February 9, 2018, 5:03am UTC](https://discourse.julialang.org/t/fail-testing-mosek-8-error-loaderror-readonlymemoryerror/8891 "2018-02-09T05:03:31Z")

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Testing Mosek on Windows with Julia v0.6.2 - 32 bits. I am trying to run this code: using JuMP using Mosek #using SCS model = Model(solver=MosekSolver()) #model = Model(solver=SCSSolver()) @variable(model, Q\[1:2, 1:2…

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## [How to handle simple events like step functions?](https://discourse.julialang.org/t/how-to-handle-simple-events-like-step-functions/8926)

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**Author:** [@Torkel](https://discourse.julialang.org/u/Torkel)\
**Replies:** 4\
**Last updated:** [February 8, 2018, 5:08pm UTC](https://discourse.julialang.org/t/how-to-handle-simple-events-like-step-functions/8926 "2018-02-08T17:08:41Z")

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Hello, In one paragraph I am trying to solve differential equations with discontinuities by solving them up to the discontinuity, change my system and input the old solution as initial conditions to a new problem. This…

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## [Eigenvalues of Hessenberg matrix (ZHSEQR)](https://discourse.julialang.org/t/eigenvalues-of-hessenberg-matrix-zhseqr/8919)

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**Author:** [@goerz](https://discourse.julialang.org/u/goerz)\
**Replies:** 2\
**Last updated:** [February 8, 2018, 8:13am UTC](https://discourse.julialang.org/t/eigenvalues-of-hessenberg-matrix-zhseqr/8919 "2018-02-08T08:13:50Z")

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Does Julia have a method to calculate the eigenvalues of a Hessenberg matrix? This would a wrapper around the ZHSEQR Lapack routine (I didn’t find anything in Base.LinAlg.LAPACK).

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## [Suggested minimal requirements for short-term plotting solution](https://discourse.julialang.org/t/suggested-minimal-requirements-for-short-term-plotting-solution/8877)

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**Author:** [@jlperla](https://discourse.julialang.org/u/jlperla)\
**Replies:** 38\
**Last updated:** [February 8, 2018, 3:10am UTC](https://discourse.julialang.org/t/suggested-minimal-requirements-for-short-term-plotting-solution/8877 "2018-02-08T03:10:21Z")

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For consideration (as discussed on Slack), here is a proposed list of requirements to try to find the best short-term (i.e. until stabilization of Makie/Plots/etc.) solution for teaching plotting for new users, students, …

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## [Running an ODEProblem until given a signal](https://discourse.julialang.org/t/running-an-odeproblem-until-given-a-signal/8913)

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**Author:** [@mindbound](https://discourse.julialang.org/u/mindbound)\
**Replies:** 2\
**Last updated:** [February 7, 2018, 11:51pm UTC](https://discourse.julialang.org/t/running-an-odeproblem-until-given-a-signal/8913 "2018-02-07T23:51:02Z")

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Is it possible for the timespan of an ODEProblem to be open-ended, i.e. for the problem to run until given an external signal (possibly via a discrete callback with an appropriate condition)? Intuitively, this would mean…

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## [Programmatic Image Tagging](https://discourse.julialang.org/t/programmatic-image-tagging/6581)

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**Author:** [@Daneel](https://discourse.julialang.org/u/Daneel)\
**Replies:** 8\
**Last updated:** [February 7, 2018, 8:03pm UTC](https://discourse.julialang.org/t/programmatic-image-tagging/6581 "2018-02-07T20:03:22Z")

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Here is my quick test of programmatic image tagging. My approach uses exiftool. The end goal is to be able to save useful metadata pertaining to plots into the saved images themselves. Definite Includes Specific keywo…

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## [SumOfSquares, JuMP; Implementing semidefinite constraint with specified domain](https://discourse.julialang.org/t/sumofsquares-jump-implementing-semidefinite-constraint-with-specified-domain/8830)

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**Author:** [@rdbrackston](https://discourse.julialang.org/u/rdbrackston)\
**Replies:** 2\
**Last updated:** [February 7, 2018, 4:02pm UTC](https://discourse.julialang.org/t/sumofsquares-jump-implementing-semidefinite-constraint-with-specified-domain/8830 "2018-02-07T16:02:51Z")

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Hello all, I am using the SumOfSquares package to obtain Lyapunov functions with some particular properties. Given a polynomial vector field defined by \\dot{x} = f(x), I wish to obtain Lyapunov functions V(x) such that …

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## [Replacement for os.path.walk in Python?](https://discourse.julialang.org/t/replacement-for-os-path-walk-in-python/8887)

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**Author:** [@amarbl](https://discourse.julialang.org/u/amarbl)\
**Replies:** 1\
**Last updated:** [February 7, 2018, 12:00pm UTC](https://discourse.julialang.org/t/replacement-for-os-path-walk-in-python/8887 "2018-02-07T12:00:14Z")

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Hi Folks, I am new to Julia, and beginning to port some machine learning projects over to Julia. One thing I am missing is the python os library which can walk a directory path quite easily. I am googling around and loo…

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## [Using results from ODEProblem while it is running](https://discourse.julialang.org/t/using-results-from-odeproblem-while-it-is-running/8874)

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**Author:** [@mindbound](https://discourse.julialang.org/u/mindbound)\
**Replies:** 2\
**Last updated:** [February 7, 2018, 1:55am UTC](https://discourse.julialang.org/t/using-results-from-odeproblem-while-it-is-running/8874 "2018-02-07T01:55:39Z")

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Hello all, I’m currently studying the documentation of DifferentialEquations.jl and trying to port my older computational neuroscience codes for using it instead of my own, less elegant and performant, ODE solvers. Whil…

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## [An illustration of Julia's beautiful design via truncated normal plots using StatsPlot.jl and Distributions.jl](https://discourse.julialang.org/t/an-illustration-of-julias-beautiful-design-via-truncated-normal-plots-using-statsplot-jl-and-distributions-jl/8876)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 0\
**Last updated:** [February 6, 2018, 10:58pm UTC](https://discourse.julialang.org/t/an-illustration-of-julias-beautiful-design-via-truncated-normal-plots-using-statsplot-jl-and-distributions-jl/8876 "2018-02-06T22:58:10Z")

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I was going to give a talk on a topic involving truncated normal distributions and I decided to write it in Julia. I googled how to do a density plot and quickly found an example for plotting the density of a normal func…

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## [How to change code on workers - Revise.jl not able](https://discourse.julialang.org/t/how-to-change-code-on-workers-revise-jl-not-able/8847)

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**Author:** [@pasha](https://discourse.julialang.org/u/pasha)\
**Replies:** 4\
**Last updated:** [February 6, 2018, 3:19pm UTC](https://discourse.julialang.org/t/how-to-change-code-on-workers-revise-jl-not-able/8847 "2018-02-06T15:19:27Z")

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I have a custom package that runs on multiple processes. If I addprocs(n); using Mypkg it will load the code to each worker (I can tell because of the annoying Nullable warnings). Now when I edit the source code, my Re…

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## [Constraints handling in JuMP/MOI](https://discourse.julialang.org/t/constraints-handling-in-jump-moi/8813)

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**Author:** [@bbrunaud](https://discourse.julialang.org/u/bbrunaud)\
**Replies:** 3\
**Last updated:** [February 6, 2018, 4:53am UTC](https://discourse.julialang.org/t/constraints-handling-in-jump-moi/8813 "2018-02-06T04:53:43Z")

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Hello all I’ve been looking at the code of the new JuMP with MOI, and I would like to understand how to update the things that are going to break in my code. In particular, I have been doing the following things Inspe…

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## [Trouble with ControlSystems.jl](https://discourse.julialang.org/t/trouble-with-controlsystems-jl/8783)

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**Author:** [@bo-lo](https://discourse.julialang.org/u/bo-lo)\
**Replies:** 13\
**Last updated:** [February 6, 2018, 1:21am UTC](https://discourse.julialang.org/t/trouble-with-controlsystems-jl/8783 "2018-02-06T01:21:01Z")

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Hi I am trying to use ControlSystems.jl to model circuits involving inductors, capacitors and resistances in the s domain. On my first try, I am getting a Zero denominator issue that I cannot debug. Here is the code (J…

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## [Gentleman's AS75 (+ Miller AS 274) Incremental WLS Algorithms](https://discourse.julialang.org/t/gentlemans-as75-miller-as-274-incremental-wls-algorithms/8822)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 7\
**Last updated:** [February 5, 2018, 9:14pm UTC](https://discourse.julialang.org/t/gentlemans-as75-miller-as-274-incremental-wls-algorithms/8822 "2018-02-05T21:14:12Z")

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Has someone already implemented Gentleman’s AS75 WLS code in Julia? It is not only fast and robust, but works nicely with adding single obs, one at a time. https://www.jstor.org/stable/2347147 https://www.jstor.org/st…

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## [Group, Mutate, Ungroup](https://discourse.julialang.org/t/group-mutate-ungroup/8819)

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**Author:** [@RandomString123](https://discourse.julialang.org/u/RandomString123)\
**Replies:** 2\
**Last updated:** [February 4, 2018, 11:18pm UTC](https://discourse.julialang.org/t/group-mutate-ungroup/8819 "2018-02-04T23:18:35Z")

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Is there a way developed to support the following workflow? I realize this example is trivial but it could be applied to more complex workflows like subgroup moving averages. And while there are ways to run calculations…

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## [JuMP; Rewriting an @eval @NLexpression with a user defined function in local scope w/ Expr](https://discourse.julialang.org/t/jump-rewriting-an-eval-nlexpression-with-a-user-defined-function-in-local-scope-w-expr/8757)

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**Author:** [@shoshievass](https://discourse.julialang.org/u/shoshievass)\
**Replies:** 6\
**Last updated:** [February 4, 2018, 4:07pm UTC](https://discourse.julialang.org/t/jump-rewriting-an-eval-nlexpression-with-a-user-defined-function-in-local-scope-w-expr/8757 "2018-02-04T16:07:45Z")

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I’m trying to use a user-defined function that takes in several distinct arguments, and then a splatted N-dim vector of parameters as an @NLexpression to be used in a constraint of an optimization problem. I described t…

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## [Parallel Map/Reduce with RemoteChannels - comments on MWE?](https://discourse.julialang.org/t/parallel-map-reduce-with-remotechannels-comments-on-mwe/8761)

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**Author:** [@pasha](https://discourse.julialang.org/u/pasha)\
**Replies:** 3\
**Last updated:** [February 3, 2018, 11:40pm UTC](https://discourse.julialang.org/t/parallel-map-reduce-with-remotechannels-comments-on-mwe/8761 "2018-02-03T23:40:18Z")

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Greetings, I’m working on a project that is a candidate for parallel map/reduce. So, I wrote a MWE of a framework for doing that below, using RemoteChannels and remote\_do(), and am interested in feedback. I’m just com…

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## [A Julian function interpolation library?](https://discourse.julialang.org/t/a-julian-function-interpolation-library/8721)

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**Author:** [@MaximilianJHuber](https://discourse.julialang.org/u/MaximilianJHuber)\
**Replies:** 5\
**Last updated:** [February 3, 2018, 8:45am UTC](https://discourse.julialang.org/t/a-julian-function-interpolation-library/8721 "2018-02-03T08:45:27Z")

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When you want to interpolate a function (match its values on some grid points and approximate it off grid) you: Generate a matrix with evaluations of basis function on the grid and find a linear combination of those th…

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## [Build issues of Ipopt](https://discourse.julialang.org/t/build-issues-of-ipopt/7095)

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**Author:** [@Rahul\_Sharma](https://discourse.julialang.org/u/Rahul_Sharma)\
**Replies:** 4\
**Last updated:** [February 2, 2018, 9:13am UTC](https://discourse.julialang.org/t/build-issues-of-ipopt/7095 "2018-02-02T09:13:49Z")

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Hi all, I am trying to install CoinOptServces package. But, the Ipopt package in it has build issues. It seems that the process ./get.Blas had an error (ProcessExited(1)). How do I install the package without any probe…

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## [JuMP User-Defined Function, Value and Gradient At Once](https://discourse.julialang.org/t/jump-user-defined-function-value-and-gradient-at-once/8681)

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**Author:** [@nhipsman](https://discourse.julialang.org/u/nhipsman)\
**Replies:** 3\
**Last updated:** [February 1, 2018, 8:27pm UTC](https://discourse.julialang.org/t/jump-user-defined-function-value-and-gradient-at-once/8681 "2018-02-01T20:27:26Z")

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Hi - I have a user-defined function for which I have an analytical gradient I’d like to use. Furthermore, most of the effort in calculating that gradient is already done in calculating the value of the function. Is th…

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