# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=553

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**Page:** 554

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## [How to check if LU factorization failed?](https://discourse.julialang.org/t/how-to-check-if-lu-factorization-failed/5553)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 29\
**Last updated:** [September 20, 2017, 10:41pm UTC](https://discourse.julialang.org/t/how-to-check-if-lu-factorization-failed/5553 "2017-09-20T22:41:17Z")

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I am currently using lufact() in a project, but I couldn’t figure out by just reading the docs how one can check if the factorization failed. Normally, one would check if the pivots are zero, but how to do that with the …

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## [Any interest in a JavaScript to julia translating tool?](https://discourse.julialang.org/t/any-interest-in-a-javascript-to-julia-translating-tool/6011)

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**Author:** [@TravisA9](https://discourse.julialang.org/u/TravisA9)\
**Replies:** 0\
**Last updated:** [September 20, 2017, 9:19pm UTC](https://discourse.julialang.org/t/any-interest-in-a-javascript-to-julia-translating-tool/6011 "2017-09-20T21:19:44Z")

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Just wanted to see how much interest there is in having a tool for translating js to jl? Any old js projects you have been meaning to port to julia? …in my case I once made a script to make a really rough translation. I…

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## [Reading and processing Data files concurrently](https://discourse.julialang.org/t/reading-and-processing-data-files-concurrently/5972)

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**Author:** [@Fred](https://discourse.julialang.org/u/Fred)\
**Replies:** 18\
**Last updated:** [September 20, 2017, 8:15pm UTC](https://discourse.julialang.org/t/reading-and-processing-data-files-concurrently/5972 "2017-09-20T20:15:11Z")

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Hi, I have many data files to process (calculate the median of each row and then compare the medians together) and I would like top process them in parallel since the first steps are independent. I tried the following …

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## [Quick way to find tight constraints?](https://discourse.julialang.org/t/quick-way-to-find-tight-constraints/5975)

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**Author:** [@Halil1](https://discourse.julialang.org/u/Halil1)\
**Replies:** 2\
**Last updated:** [September 20, 2017, 7:27pm UTC](https://discourse.julialang.org/t/quick-way-to-find-tight-constraints/5975 "2017-09-20T19:27:08Z")

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Hello all, Is there a straight-forward method for understanding which constraints of the model are tight? I will run some scenarios which I will change multiple parameters at a time, so just curious if there is any qui…

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## [TensorFlow : CPU warnings](https://discourse.julialang.org/t/tensorflow-cpu-warnings/5993)

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**Author:** [@Colin\_Beckingham](https://discourse.julialang.org/u/Colin_Beckingham)\
**Replies:** 4\
**Last updated:** [September 20, 2017, 2:12pm UTC](https://discourse.julialang.org/t/tensorflow-cpu-warnings/5993 "2017-09-20T14:12:14Z")

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Each time I run a TF programme it runs fine but starts out warning me in about 20 lines of messages that I really should be putting my Intel CPU to better use by using the MKL instructions. So I put several hours into tr…

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## [How to know which plotting backend is in use?](https://discourse.julialang.org/t/how-to-know-which-plotting-backend-is-in-use/5987)

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**Author:** [@chobbes](https://discourse.julialang.org/u/chobbes)\
**Replies:** 6\
**Last updated:** [September 20, 2017, 12:35pm UTC](https://discourse.julialang.org/t/how-to-know-which-plotting-backend-is-in-use/5987 "2017-09-20T12:35:33Z")

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I know how to switch between backends following the Plots tutorial. Is there a way to check which backend is in use? Didn’t search the tutorial carefully. Thanks in advance for a pointer if I’ve missed it …

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## [Editing fontstyle for colorbar](https://discourse.julialang.org/t/editing-fontstyle-for-colorbar/5967)

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**Author:** [@AnkurD](https://discourse.julialang.org/u/AnkurD)\
**Replies:** 3\
**Last updated:** [September 20, 2017, 1:42am UTC](https://discourse.julialang.org/t/editing-fontstyle-for-colorbar/5967 "2017-09-20T01:42:05Z")

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I was trying to adjust the colorbar fonts in my heatmap, but I realized that there is no option to do so through PyPlot (or any other backend for that matter). I could just go back and call matplotlib directly, but that …

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## [JuliaDB problems](https://discourse.julialang.org/t/juliadb-problems/5970)

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**Author:** [@johann.spies](https://discourse.julialang.org/u/johann.spies)\
**Replies:** 2\
**Last updated:** [September 19, 2017, 2:30pm UTC](https://discourse.julialang.org/t/juliadb-problems/5970 "2017-09-19T14:30:36Z")

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I am unable to use JuliaDB. The following says it all: julia\> using JuliaDB julia\> path = Pkg.dir(“home”, “js”, “db\_docs”, “sql”, “projects”, “basic\_sciences”, “juliadb”) “/home/js/.julia/v0.6/home/js/db\_docs/sql/pro…

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## [Variable number of Nonlinear Constraints by user-defined functions](https://discourse.julialang.org/t/variable-number-of-nonlinear-constraints-by-user-defined-functions/5895)

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**Author:** [@Pu\_He](https://discourse.julialang.org/u/Pu_He)\
**Replies:** 1\
**Last updated:** [September 19, 2017, 12:13pm UTC](https://discourse.julialang.org/t/variable-number-of-nonlinear-constraints-by-user-defined-functions/5895 "2017-09-19T12:13:40Z")

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Hi there, Sorry about the formatting on a previous version of the post. I am new to Julia and doing research in demand modelling. And I apologize if this is too basic. I am thinking to move my code from Rcpp to Julia to…

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## [Mute solver output](https://discourse.julialang.org/t/mute-solver-output/5108)

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**Author:** [@leclere](https://discourse.julialang.org/u/leclere)\
**Replies:** 2\
**Last updated:** [September 19, 2017, 12:08pm UTC](https://discourse.julialang.org/t/mute-solver-output/5108 "2017-09-19T12:08:33Z")

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Hi all, some 3 years ago people seemed to thought that having a standard mute option in JuMP would be a soon to be feature (see e.g. Redirecting to Google Groups). Has there been any progress on the subject ? At the mo…

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## [TensorFlow : explicit close session?](https://discourse.julialang.org/t/tensorflow-explicit-close-session/5952)

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**Author:** [@Colin\_Beckingham](https://discourse.julialang.org/u/Colin_Beckingham)\
**Replies:** 2\
**Last updated:** [September 19, 2017, 1:54am UTC](https://discourse.julialang.org/t/tensorflow-explicit-close-session/5952 "2017-09-19T01:54:50Z")

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The Python API calls for an explicit close of the session according to example code I have seen. The docs for Julia seem to indicate there is no close() on a session. Would this be a Python/Julia difference to add to the…

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## [Best way to get pieces of a parquet into a dataframe](https://discourse.julialang.org/t/best-way-to-get-pieces-of-a-parquet-into-a-dataframe/5949)

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**Author:** [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Replies:** 0\
**Last updated:** [September 18, 2017, 3:34pm UTC](https://discourse.julialang.org/t/best-way-to-get-pieces-of-a-parquet-into-a-dataframe/5949 "2017-09-18T15:34:22Z")

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I’m looking for a minimal working example for loading some part of a parquet file into a dataframe and vice versa. I’m assuming that the only way to do this currently is with Spark.jl. Right now I don’t even know if th…

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## [TensorFlow : train.restore](https://discourse.julialang.org/t/tensorflow-train-restore/5948)

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**Author:** [@Colin\_Beckingham](https://discourse.julialang.org/u/Colin_Beckingham)\
**Replies:** 2\
**Last updated:** [September 18, 2017, 3:33pm UTC](https://discourse.julialang.org/t/tensorflow-train-restore/5948 "2017-09-18T15:33:45Z")

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I’m trying to familiarize with the sample code which runs correctly. There is a line in the epoch iteration train.save(…) which saves a number of binary files labelled from 95 to 99. I understand that they can be recove…

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## [Plotting with Julia using Java Plots](https://discourse.julialang.org/t/plotting-with-julia-using-java-plots/5920)

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**Author:** [@sterg](https://discourse.julialang.org/u/sterg)\
**Replies:** 4\
**Last updated:** [September 17, 2017, 3:18pm UTC](https://discourse.julialang.org/t/plotting-with-julia-using-java-plots/5920 "2017-09-17T15:18:46Z")

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Hi all! I started to learn Julia, and yes, it is a superb language!! However, plotting seems difficult, thus I started a project aimed to connect Java platform independent graphics, with Julia, tis nis project can b…

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## [Packages for signal decomposition](https://discourse.julialang.org/t/packages-for-signal-decomposition/5909)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 4\
**Last updated:** [September 15, 2017, 8:52pm UTC](https://discourse.julialang.org/t/packages-for-signal-decomposition/5909 "2017-09-15T20:52:19Z")

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What are the packages out there for decomposing a signal into a basis of functions? Fourier basis, Radial basis, Cosine basis, … I need to decompose a signal into a set of basis functions and coefficients, manipulate th…

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## [Vectorized Convex inequality constraint](https://discourse.julialang.org/t/vectorized-convex-inequality-constraint/5890)

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**Author:** [@jacob-roth](https://discourse.julialang.org/u/jacob-roth)\
**Replies:** 2\
**Last updated:** [September 15, 2017, 2:36pm UTC](https://discourse.julialang.org/t/vectorized-convex-inequality-constraint/5890 "2017-09-15T14:36:34Z")

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I’m trying to vectorize an inequality constraint comparing two Convex types. On one side, I have Convex.MaxAtoms, and on the other side, I have Variables. SO link here. I want to do something like the following: using C…

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## [Bug or wrong code?](https://discourse.julialang.org/t/bug-or-wrong-code/5908)

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**Author:** [@Yaroslav\_Kavenchuk](https://discourse.julialang.org/u/Yaroslav_Kavenchuk)\
**Replies:** 0\
**Last updated:** [September 15, 2017, 1:33pm UTC](https://discourse.julialang.org/t/bug-or-wrong-code/5908 "2017-09-15T13:33:36Z")

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echo-server.jl: @everywhere function parallel\_echo\_server(port::Int=8080; debug::Bool=false) (port, server) = listenany(port) debug && println(STDERR, "\[SERVER\] Server started!") n = nprocs() while true let …

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## [Initialization Error: ODBC](https://discourse.julialang.org/t/initialization-error-odbc/5884)

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**Author:** [@jasoriya](https://discourse.julialang.org/u/jasoriya)\
**Replies:** 1\
**Last updated:** [September 14, 2017, 12:25pm UTC](https://discourse.julialang.org/t/initialization-error-odbc/5884 "2017-09-14T12:25:48Z")

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I am working with Julia 0.5.2 and I added ODBC package Pkg.add ("ODBC") On running Using ODBC I get the following error: LoadError: InitError: ccall: could not find function SQLAllocHandle in library during initi…

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## [How to measure/read size of the optimization model?](https://discourse.julialang.org/t/how-to-measure-read-size-of-the-optimization-model/5855)

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**Author:** [@Halil1](https://discourse.julialang.org/u/Halil1)\
**Replies:** 2\
**Last updated:** [September 12, 2017, 7:54pm UTC](https://discourse.julialang.org/t/how-to-measure-read-size-of-the-optimization-model/5855 "2017-09-12T19:54:09Z")

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Hello all, I really need some help with some conceptual thinking and Julia output regarding to size of an optimization model. Trying to read the size of the optimization model from Julia output. Is there an easy way to…

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## [How do I deal with Random Number generation when multithreading](https://discourse.julialang.org/t/how-do-i-deal-with-random-number-generation-when-multithreading/5636)

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**Author:** [@vgdev](https://discourse.julialang.org/u/vgdev)\
**Replies:** 6\
**Last updated:** [August 31, 2017, 12:34pm UTC](https://discourse.julialang.org/t/how-do-i-deal-with-random-number-generation-when-multithreading/5636 "2017-08-31T12:34:43Z")

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If I am using Threads.@threads to run my Monte Carlo simulation in paralell, how do I set up Mersenne Twister RNGs for each thread so that I am both able to set a seed, in order to be able to reproduce the results, but …

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## [Error when grouping using Query.jl](https://discourse.julialang.org/t/error-when-grouping-using-query-jl/5809)

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**Author:** [@innerlee](https://discourse.julialang.org/u/innerlee)\
**Replies:** 1\
**Last updated:** [September 11, 2017, 9:10pm UTC](https://discourse.julialang.org/t/error-when-grouping-using-query-jl/5809 "2017-09-11T21:10:18Z")

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Let the data sourse be a list of Dicts: julia\> as = \[Dict("id" =\> "a", "v" =\> 1), Dict("id" =\> "b", "v" =\> 2)\] Then we group them by id julia\> using Query julia\> @from a in as begin @group a by a…

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## [Announcing new Packages and Solvers for Multi-objective Mixed Integer Programming ( with JuMP extension )](https://discourse.julialang.org/t/announcing-new-packages-and-solvers-for-multi-objective-mixed-integer-programming-with-jump-extension/5814)

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**Author:** [@Aritra\_Pal](https://discourse.julialang.org/u/Aritra_Pal)\
**Replies:** 4\
**Last updated:** [September 11, 2017, 3:06pm UTC](https://discourse.julialang.org/t/announcing-new-packages-and-solvers-for-multi-objective-mixed-integer-programming-with-jump-extension/5814 "2017-09-11T15:06:52Z")

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Hi everyone, I am excited to announce 5 new packages for solving Multiobjective Mixed Integer Linear Programs: FPBH.jl: It is a linear programming based heuristic for computing an approximate nondominated frontier of …

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## [Efficiently reusing/updating Julia's Convex constraints](https://discourse.julialang.org/t/efficiently-reusing-updating-julias-convex-constraints/5811)

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**Author:** [@jacob-roth](https://discourse.julialang.org/u/jacob-roth)\
**Replies:** 3\
**Last updated:** [September 11, 2017, 12:24pm UTC](https://discourse.julialang.org/t/efficiently-reusing-updating-julias-convex-constraints/5811 "2017-09-11T12:24:38Z")

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Not sure if this is the appropriate place to ask my question or if StackOverflow is better. Anyway, my question is related to reusing constraints in the Convex package. I have something like the following simplified str…

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## [Collection of JuMP variables](https://discourse.julialang.org/t/collection-of-jump-variables/5798)

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**Author:** [@leclere](https://discourse.julialang.org/u/leclere)\
**Replies:** 6\
**Last updated:** [September 11, 2017, 12:06pm UTC](https://discourse.julialang.org/t/collection-of-jump-variables/5798 "2017-09-11T12:06:51Z")

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Hello, I would like to define an array of jump variables, e.g something like for c:1:C @variable(model, mu\[c\]\[1:foo(c)\] \>= 0) end or maybe for c:1:C mu\[c\] = @variable(model, \[1:foo(c)\] \>= 0) end but I was no…

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## [Is wrapping GPUQREngine anywhere on the agenda?](https://discourse.julialang.org/t/is-wrapping-gpuqrengine-anywhere-on-the-agenda/5755)

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**Author:** [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)\
**Replies:** 4\
**Last updated:** [September 9, 2017, 7:47am UTC](https://discourse.julialang.org/t/is-wrapping-gpuqrengine-anywhere-on-the-agenda/5755 "2017-09-09T07:47:39Z")

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Is there any simple way to do QR decomposition of a sparse matrix on the GPU in Julia? I believe GPUQREngine of SuiteSparse is an obvious choice to wrap, so I wonder if anyone has gotten around to do it, or if it is anyw…

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## [Conditional logit models for paired data](https://discourse.julialang.org/t/conditional-logit-models-for-paired-data/5790)

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**Author:** [@mwsohn](https://discourse.julialang.org/u/mwsohn)\
**Replies:** 2\
**Last updated:** [September 9, 2017, 2:40am UTC](https://discourse.julialang.org/t/conditional-logit-models-for-paired-data/5790 "2017-09-09T02:40:33Z")

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Can MixedModels fit conditional logistic regression models for paired data? If so, I would appreciate a sample syntax.

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## [Proposal: Using a "mask" for DataFrames and ModelMatrices](https://discourse.julialang.org/t/proposal-using-a-mask-for-dataframes-and-modelmatrices/5779)

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**Author:** [@jeffwong](https://discourse.julialang.org/u/jeffwong)\
**Replies:** 3\
**Last updated:** [September 8, 2017, 11:46pm UTC](https://discourse.julialang.org/t/proposal-using-a-mask-for-dataframes-and-modelmatrices/5779 "2017-09-08T23:46:00Z")

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In data science we always have a need to split data into a training set and a test set. Sometimes we will do this multiple times like in k fold cross validation, or leave one out cross validations. In R: the typical par…

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## [What is the dx used in finite difference approximation in Calculus.jl?](https://discourse.julialang.org/t/what-is-the-dx-used-in-finite-difference-approximation-in-calculus-jl/5773)

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**Author:** [@vgdev](https://discourse.julialang.org/u/vgdev)\
**Replies:** 3\
**Last updated:** [September 8, 2017, 4:29pm UTC](https://discourse.julialang.org/t/what-is-the-dx-used-in-finite-difference-approximation-in-calculus-jl/5773 "2017-09-08T16:29:58Z")

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I tried to find what the value of \\Delta x that is used in Calculus.jl for finite difference approximation (i.e. for a forward scheme \\frac{f(x+\\Delta x)-f(x)}{\\Delta x }), without luck. Is there a way to retreive it mys…

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## [Accuracy of BigFloat - Calculating sin with high accuracy](https://discourse.julialang.org/t/accuracy-of-bigfloat-calculating-sin-with-high-accuracy/4604)

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**Author:** [@timer](https://discourse.julialang.org/u/timer)\
**Replies:** 8\
**Last updated:** [September 7, 2017, 4:57pm UTC](https://discourse.julialang.org/t/accuracy-of-bigfloat-calculating-sin-with-high-accuracy/4604 "2017-09-07T16:57:07Z")

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Hello, I’am trying to calcuate values of the sin-function to high precision. I want to get at least 1 million valid digits. Using the following code I test the accuracy of BigFloat: # Set precision to 7 million bits, …

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## [JuMP package: Cannot display the values of decision variable](https://discourse.julialang.org/t/jump-package-cannot-display-the-values-of-decision-variable/5745)

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**Author:** [@Halil1](https://discourse.julialang.org/u/Halil1)\
**Replies:** 5\
**Last updated:** [September 7, 2017, 3:38pm UTC](https://discourse.julialang.org/t/jump-package-cannot-display-the-values-of-decision-variable/5745 "2017-09-07T15:38:20Z")

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Hello everyone, I have coded a mixed-integer linear optimization model. I am having trouble displaying the decision variable results. I have a decision variable: @variable(m, 0 \<= Y\[i in I,j in J\] \<=1) It is optimal…

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