# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1901

[Latest](https://discourse.julialang.org/latest.md) · [Categories](https://discourse.julialang.org/categories.md) · [Tags](https://discourse.julialang.org/tags.md)

**Page:** 1902

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## [Problem with using ODE solvers with autodifferentiation](https://discourse.julialang.org/t/problem-with-using-ode-solvers-with-autodifferentiation/29808)

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**Author:** [@Nirvik](https://discourse.julialang.org/u/Nirvik)\
**Replies:** 8\
**Last updated:** [October 15, 2019, 11:36pm UTC](https://discourse.julialang.org/t/problem-with-using-ode-solvers-with-autodifferentiation/29808 "2019-10-15T23:36:25Z")

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I am using the DifferentialEquations package to simulate Hodgkin Huxley neurons. This involves evaluating certain parameters inside the ODE function using dependent variables for which I need to make function calls from …

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## [DataFrames, best way to import from JSON format file](https://discourse.julialang.org/t/dataframes-best-way-to-import-from-json-format-file/29946)

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**Author:** [@4aHxKzD](https://discourse.julialang.org/u/4aHxKzD)\
**Replies:** 6\
**Last updated:** [October 15, 2019, 10:55pm UTC](https://discourse.julialang.org/t/dataframes-best-way-to-import-from-json-format-file/29946 "2019-10-15T22:55:03Z")

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Hi. I’m coming from Python and would like to know what is the current “standard” on how to import from a JSON file to a DataFrame data structure, i.e., the equivalent to pandas.read\_json().

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## [New LLVM JIT Features](https://discourse.julialang.org/t/new-llvm-jit-features/22754)

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**Author:** [@preejackie](https://discourse.julialang.org/u/preejackie)\
**Replies:** 13\
**Last updated:** [October 15, 2019, 8:26pm UTC](https://discourse.julialang.org/t/new-llvm-jit-features/22754 "2019-10-15T20:26:53Z")

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Hi I’m working on developing a Speculative compilation support in LLVM ORC JIT Infrastructure. As LLVM ORC supports compiling in multiple backend threads, it would be effective if we compile the functions speculatively…

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## [Problem writing data to a file after printing it](https://discourse.julialang.org/t/problem-writing-data-to-a-file-after-printing-it/29919)

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**Author:** [@rverdier](https://discourse.julialang.org/u/rverdier)\
**Replies:** 5\
**Last updated:** [October 15, 2019, 8:12pm UTC](https://discourse.julialang.org/t/problem-writing-data-to-a-file-after-printing-it/29919 "2019-10-15T20:12:42Z")

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The following script, taken from a complicated encoding/decoding application for a course I’m preparing, illustrates a problem with a data vector in which printing it and then writing it to a file creates an empty file,…

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## [Benchmark MATLAB & Julia for Matrix Operations](https://discourse.julialang.org/t/benchmark-matlab-julia-for-matrix-operations/2000)

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**Author:** [@RoyiAvital](https://discourse.julialang.org/u/RoyiAvital)\
**Replies:** 148\
**Last updated:** [October 15, 2019, 8:00pm UTC](https://discourse.julialang.org/t/benchmark-matlab-julia-for-matrix-operations/2000 "2019-10-15T20:00:15Z")

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Hi, My first try with Julia was to compare its speed on Matrix Operations (Linear Algebra oriented) to MATLAB. Benchmark MATLAB & Julia for Matrix Operations As any test, it is far from being perfect, but it is tellin…

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## [Puzzling behavior of icxx](https://discourse.julialang.org/t/puzzling-behavior-of-icxx/29950)

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**Author:** [@Josiah\_Slack](https://discourse.julialang.org/u/Josiah_Slack)\
**Replies:** 1\
**Last updated:** [October 15, 2019, 7:35pm UTC](https://discourse.julialang.org/t/puzzling-behavior-of-icxx/29950 "2019-10-15T19:35:32Z")

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I’m using Cxx, and my use case involves converting std::vector return values into Julia arrays. I’m able to define my functions in the REPL, and everything behaves as I would expect. However, if I wrap all this in a modu…

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## [Univariate linear regression with each covariate of dataframe](https://discourse.julialang.org/t/univariate-linear-regression-with-each-covariate-of-dataframe/29951)

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**Author:** [@sergevic](https://discourse.julialang.org/u/sergevic)\
**Replies:** 5\
**Last updated:** [October 15, 2019, 7:16pm UTC](https://discourse.julialang.org/t/univariate-linear-regression-with-each-covariate-of-dataframe/29951 "2019-10-15T19:16:47Z")

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I have a dataframe with 5 covariates X1, X2, X3, X4, X5 and a dependent variable Y. I have to perform a univariate regression of Y on each covariate. I don’t want to do using GLM lm(@formula(Y~X1), data) lm(@formula(Y~X…

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## [Chicago meetup Monday, May 21](https://discourse.julialang.org/t/chicago-meetup-monday-may-21/10919)

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**Author:** [@mbauman](https://discourse.julialang.org/u/mbauman)\
**Replies:** 3\
**Last updated:** [October 15, 2019, 5:51pm UTC](https://discourse.julialang.org/t/chicago-meetup-monday-may-21/10919 "2019-10-15T17:51:37Z")

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Monday, May 21, 2018 5:00 PM to 7:00 PM UBS Tower, 1 N. Wacker 1.0 is right around the corner! Meet the new local organizer and discuss potential topics for future sessions, and strategies for getting Julia into yo…

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## [Julia vs Python's Dask: Known speed comparisons?](https://discourse.julialang.org/t/julia-vs-pythons-dask-known-speed-comparisons/29459)

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**Author:** [@joshhjacobson](https://discourse.julialang.org/u/joshhjacobson)\
**Replies:** 13\
**Last updated:** [October 15, 2019, 3:58pm UTC](https://discourse.julialang.org/t/julia-vs-pythons-dask-known-speed-comparisons/29459 "2019-10-15T15:58:16Z")

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Hi all, I’m new to the Julia community and have arrived in hopes of improving the speed of parallelization tasks I’ve been running with Dask (distributed) in Python. I know there are some Julia packages that are inspire…

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## [Difference between Tables.jl and DataFrames.jl](https://discourse.julialang.org/t/difference-between-tables-jl-and-dataframes-jl/29944)

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**Author:** [@4aHxKzD](https://discourse.julialang.org/u/4aHxKzD)\
**Replies:** 1\
**Last updated:** [October 15, 2019, 3:16pm UTC](https://discourse.julialang.org/t/difference-between-tables-jl-and-dataframes-jl/29944 "2019-10-15T15:16:17Z")

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Hi. Is anyone here kind enough to educate me about what is the difference between Tables.jl and DataFrames.jl packages?

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## [Trying to build Julia, downloaded file checksum failure](https://discourse.julialang.org/t/trying-to-build-julia-downloaded-file-checksum-failure/29795)

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**Author:** [@BioTurboNick](https://discourse.julialang.org/u/BioTurboNick)\
**Replies:** 6\
**Last updated:** [October 15, 2019, 3:01pm UTC](https://discourse.julialang.org/t/trying-to-build-julia-downloaded-file-checksum-failure/29795 "2019-10-15T15:01:21Z")

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I’m trying to build julia myself from 1.2.0 so I can play with the parser. (If there’s an easier way to just do that, please let me know :slight\_smile: ) ‘make’ is downloading a file and it fails with a reported checksu…

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## [Does @spawn with threads give speedup?](https://discourse.julialang.org/t/does-spawn-with-threads-give-speedup/29932)

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**Author:** [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)\
**Replies:** 2\
**Last updated:** [October 15, 2019, 2:41pm UTC](https://discourse.julialang.org/t/does-spawn-with-threads-give-speedup/29932 "2019-10-15T14:41:46Z")

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So far I haven’t gotten any. Anyone’s been successful?

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## [Numpy 10x faster than Julia ?! What am I doing wrong ?! \[solved - julia faster now\]](https://discourse.julialang.org/t/numpy-10x-faster-than-julia-what-am-i-doing-wrong-solved-julia-faster-now/29922)

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**Author:** [@joak](https://discourse.julialang.org/u/joak)\
**Replies:** 37\
**Last updated:** [October 15, 2019, 11:52am UTC](https://discourse.julialang.org/t/numpy-10x-faster-than-julia-what-am-i-doing-wrong-solved-julia-faster-now/29922 "2019-10-15T11:52:25Z")

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With numpy I get ~100ns per element With julia ~1200ns I must be missing something… How can I reach same speed with julia ? Code below: Python: import time import numpy as np from numpy import sin, cos def f(p): …

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## [Keyword argument method without overwriting original method](https://discourse.julialang.org/t/keyword-argument-method-without-overwriting-original-method/29927)

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**Author:** [@Amin\_Yahyaabadi](https://discourse.julialang.org/u/Amin_Yahyaabadi)\
**Replies:** 3\
**Last updated:** [October 15, 2019, 9:32am UTC](https://discourse.julialang.org/t/keyword-argument-method-without-overwriting-original-method/29927 "2019-10-15T09:32:16Z")

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julia\> fun(x::Integer) = 1 fun (generic function with 1 method) julia\> fun(x::Integer; y::Array) = 1 fun (generic function with 1 method) julia\> fun(x::Integer, y::Array) = 1 fun (generic function with 2 methods) Why …

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## [ROS2 client library for Julia](https://discourse.julialang.org/t/ros2-client-library-for-julia/29929)

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**Author:** [@andreasziegler](https://discourse.julialang.org/u/andreasziegler)\
**Replies:** 0\
**Last updated:** [October 15, 2019, 8:47am UTC](https://discourse.julialang.org/t/ros2-client-library-for-julia/29929 "2019-10-15T08:47:16Z")

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As a robotics engineer, I’m working with ROS2. From an (software) engineering perspective, I’m quite interested in Julia however with the lack of a ROS2 client library for Julia, it’s for me currently a bit difficult to …

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## [“large” scale software in Julia](https://discourse.julialang.org/t/large-scale-software-in-julia/29895)

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**Author:** [@DK1PL](https://discourse.julialang.org/u/DK1PL)\
**Replies:** 6\
**Last updated:** [October 15, 2019, 6:39am UTC](https://discourse.julialang.org/t/large-scale-software-in-julia/29895 "2019-10-15T06:39:11Z")

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Hi, I’m new to Julia and I’m learning Julia working on small private project for the HF antenna design but if I’m thinking about the “large” scale software then I don’t see currently any way to do this in Julia. For exa…

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## [Access columns by variable name with \`readdlm\` from \`DelimitedFiles\`](https://discourse.julialang.org/t/access-columns-by-variable-name-with-readdlm-from-delimitedfiles/29918)

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**Author:** [@sergevic](https://discourse.julialang.org/u/sergevic)\
**Replies:** 4\
**Last updated:** [October 15, 2019, 3:26am UTC](https://discourse.julialang.org/t/access-columns-by-variable-name-with-readdlm-from-delimitedfiles/29918 "2019-10-15T03:26:11Z")

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Once again, the documentation of Julia is useless and provides no help. I read a .txt file with the command data=readdlm("data.txt", header=true) from the DelimitedFiles package. The result is a Tuple with the data separ…

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## [I get variable not defined error in a trivial example](https://discourse.julialang.org/t/i-get-variable-not-defined-error-in-a-trivial-example/29917)

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**Author:** [@gmouts](https://discourse.julialang.org/u/gmouts)\
**Replies:** 2\
**Last updated:** [October 15, 2019, 2:10am UTC](https://discourse.julialang.org/t/i-get-variable-not-defined-error-in-a-trivial-example/29917 "2019-10-15T02:10:38Z")

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So at REPL I typed the following julia\> using Polynomials julia\> p=Poly(\[5,-3,-2,-2,1,1\]) Poly(5 - 3\*x - 2\*x^2 - 2\*x^3 + x^4 + x^5) julia\> dp=polyder(p) Poly(-3 - 4\*x - 6\*x^2 + 4\*x^3 + 5\*x^4) julia\> function newtonIt…

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## [Using JuliaDB to create larger than memory datasets and work with them?](https://discourse.julialang.org/t/using-juliadb-to-create-larger-than-memory-datasets-and-work-with-them/18724)

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**Author:** [@Juan](https://discourse.julialang.org/u/Juan)\
**Replies:** 3\
**Last updated:** [October 15, 2019, 12:55am UTC](https://discourse.julialang.org/t/using-juliadb-to-create-larger-than-memory-datasets-and-work-with-them/18724 "2019-10-15T00:55:45Z")

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JuliaDB docs explain how to perform some basic operations out-of-core, with data larger than memory. http://juliadb.org/latest/manual/out-of-core.html But it seems it can only load large data and produce small results. …

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## [Optional use of commas](https://discourse.julialang.org/t/optional-use-of-commas/29757)

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**Author:** [@TravisA9](https://discourse.julialang.org/u/TravisA9)\
**Replies:** 15\
**Last updated:** [October 15, 2019, 12:40am UTC](https://discourse.julialang.org/t/optional-use-of-commas/29757 "2019-10-15T00:40:26Z")

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I’ve been thinking about the use of commas in code for a long time now, and am curious to see what observations others can make on the matter. The idea is this; commas are mostly (technically) unneeded in various program…

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## [Cannot add or dev a specific package](https://discourse.julialang.org/t/cannot-add-or-dev-a-specific-package/29915)

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**Author:** [@jocklawrie](https://discourse.julialang.org/u/jocklawrie)\
**Replies:** 2\
**Last updated:** [October 15, 2019, 12:16am UTC](https://discourse.julialang.org/t/cannot-add-or-dev-a-specific-package/29915 "2019-10-15T00:16:10Z")

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Hi all, I am trying to add a package in a private repository to a new project. I get the error below. I’ve had no trouble adding packages in the same repository to the same project. I also can’t dev the package. Any…

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## [Lab streaming layer](https://discourse.julialang.org/t/lab-streaming-layer/11033)

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**Author:** [@\_rob](https://discourse.julialang.org/u/_rob)\
**Replies:** 2\
**Last updated:** [October 14, 2019, 11:18pm UTC](https://discourse.julialang.org/t/lab-streaming-layer/11033 "2019-10-14T23:18:09Z")

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Does anyone have any experience using lab streaming layer (LSL) with Julia? Or know of any packages that do? Specifically I am trying to stream my data from acquisition machines to another computer where Julia will proce…

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## [Autodiff : Custom derivatives of vector functions for linear algebra](https://discourse.julialang.org/t/autodiff-custom-derivatives-of-vector-functions-for-linear-algebra/22826)

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**Author:** [@sdewaele](https://discourse.julialang.org/u/sdewaele)\
**Replies:** 15\
**Last updated:** [October 14, 2019, 10:23pm UTC](https://discourse.julialang.org/t/autodiff-custom-derivatives-of-vector-functions-for-linear-algebra/22826 "2019-10-14T22:23:51Z")

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Is there a solution for automatic differentiation through code that contains a number of linear algebra operations including, for example, lyap and the matrix exponential exponential (exp)? This type of linear algebra oc…

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## [Declaring Int256?](https://discourse.julialang.org/t/declaring-int256/29911)

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**Author:** [@squirrel](https://discourse.julialang.org/u/squirrel)\
**Replies:** 1\
**Last updated:** [October 14, 2019, 8:50pm UTC](https://discourse.julialang.org/t/declaring-int256/29911 "2019-10-14T20:50:19Z")

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Julia’s documentation describes how primitive integers are declared here: https://docs.julialang.org/en/v1/manual/types/#Primitive-Types-1 I want to use an Int256, but this throws an error: primitive type Int256 \<: S…

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## [Using Plots.jl with pgfplots() backend](https://discourse.julialang.org/t/using-plots-jl-with-pgfplots-backend/29740)

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**Author:** [@thehalfspace](https://discourse.julialang.org/u/thehalfspace)\
**Replies:** 1\
**Last updated:** [October 14, 2019, 8:24pm UTC](https://discourse.julialang.org/t/using-plots-jl-with-pgfplots-backend/29740 "2019-10-14T20:24:27Z")

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I am using MacOS. I have been a long-time PyPlot user and I want to switch to Plots.jl My setup is using vim and julia REPL in a terminal side-by-side. I have the following set of very basic questions: When I use pg…

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## [DataFrames: removing columns with many missing values](https://discourse.julialang.org/t/dataframes-removing-columns-with-many-missing-values/29907)

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**Author:** [@johnbb](https://discourse.julialang.org/u/johnbb)\
**Replies:** 2\
**Last updated:** [October 14, 2019, 7:33pm UTC](https://discourse.julialang.org/t/dataframes-removing-columns-with-many-missing-values/29907 "2019-10-14T19:33:08Z")

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How can I remove columns with more than 10% missing data from a DataFrame? In R it would be x\[, colMeans(is.na(x)) \< 0.1\]. Thanks!

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## [IQVIA - Hiring for a senior software engineer for our London,UK team](https://discourse.julialang.org/t/iqvia-hiring-for-a-senior-software-engineer-for-our-london-uk-team/29894)

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**Author:** [@Richie](https://discourse.julialang.org/u/Richie)\
**Replies:** 1\
**Last updated:** [October 14, 2019, 6:18pm UTC](https://discourse.julialang.org/t/iqvia-hiring-for-a-senior-software-engineer-for-our-london-uk-team/29894 "2019-10-14T18:18:57Z")

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Hi all, We have an opening within our AI Machine Learning team here in London for an experienced software developer.:blush: :computer: The role will be working full time with Julia so experience with the language is de…

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## [Dictionary comprehension with interdependent variables](https://discourse.julialang.org/t/dictionary-comprehension-with-interdependent-variables/29909)

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**Author:** [@marcusps](https://discourse.julialang.org/u/marcusps)\
**Replies:** 2\
**Last updated:** [October 14, 2019, 6:00pm UTC](https://discourse.julialang.org/t/dictionary-comprehension-with-interdependent-variables/29909 "2019-10-14T18:00:58Z")

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I want to build a dictionary that corresponds to an lower triangular array (i.e., a\[i,j\] only exists if i\>j). How can I write a dictionary comprehension that achieves this? I tried Dict( (i,j) =\> f(i,j) for j in i+1:N…

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## [Coursera's Julia Scientific Programming course really sucks!](https://discourse.julialang.org/t/courseras-julia-scientific-programming-course-really-sucks/29837)

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**Author:** [@aerdely](https://discourse.julialang.org/u/aerdely)\
**Replies:** 7\
**Last updated:** [October 14, 2019, 5:02pm UTC](https://discourse.julialang.org/t/courseras-julia-scientific-programming-course-really-sucks/29837 "2019-10-14T17:02:19Z")

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Coursera’s introductory course: https://www.coursera.org/learn/julia-programming really sucks! Bad publicity, I would say. Dumb examples and quizes, low video and image quality, coding errors :grimacing: I think Julia …

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## [Enable interpolation when doing Meta.parse()](https://discourse.julialang.org/t/enable-interpolation-when-doing-meta-parse/29906)

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**Author:** [@AlwaysPS](https://discourse.julialang.org/u/AlwaysPS)\
**Replies:** 0\
**Last updated:** [October 14, 2019, 3:28pm UTC](https://discourse.julialang.org/t/enable-interpolation-when-doing-meta-parse/29906 "2019-10-14T15:28:01Z")

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I’m trying to build a toy program using the nonlinear facility of JuMP. The general structure looks like this: function solve(constraint::String) model = Model() vars = @variable(model, \[1:10\], base\_name="x") …

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