# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=518

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**Page:** 519

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## [DataTables or DataFrames?](https://discourse.julialang.org/t/datatables-or-dataframes/3160)

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**Author:** [@natashawatkins](https://discourse.julialang.org/u/natashawatkins)\
**Replies:** 32\
**Last updated:** [November 19, 2018, 4:38pm UTC](https://discourse.julialang.org/t/datatables-or-dataframes/3160 "2018-11-19T16:38:26Z")

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After a lot of reading, I’m still not certain about the state of data handling in Julia. My understanding is there is a migration over to DataTables due to type-safety considerations, however there are still a number of…

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## [Disk based data manipulation framework needed](https://discourse.julialang.org/t/disk-based-data-manipulation-framework-needed/6303)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 21\
**Last updated:** [October 31, 2017, 8:20pm UTC](https://discourse.julialang.org/t/disk-based-data-manipulation-framework-needed/6303 "2017-10-31T20:20:04Z")

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SAS is big in the corporate world. I work in the finance industry and SAS is still quite big. To be honest, using SAS is a pain. SAS can’t even syntax highlight its own language properly. But it’s still there because it …

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## [Challenge: Hopf Fibration using Julia](https://discourse.julialang.org/t/challenge-hopf-fibration-using-julia/17697)

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**Author:** [@jandehaan](https://discourse.julialang.org/u/jandehaan)\
**Replies:** 2\
**Last updated:** [November 19, 2018, 11:30am UTC](https://discourse.julialang.org/t/challenge-hopf-fibration-using-julia/17697 "2018-11-19T11:30:07Z")

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If you are looking for a visualization challenge, try visualizing Hopf Fibrations. Niles Johnson was able to do it using the free mathematics software Sage including the Tachyon ray tracer. Visualization - Lecture -…

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## [Incorrect results for sinpi and cospi when using fastmath mode?](https://discourse.julialang.org/t/incorrect-results-for-sinpi-and-cospi-when-using-fastmath-mode/17662)

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**Author:** [@Seif\_Shebl](https://discourse.julialang.org/u/Seif_Shebl)\
**Replies:** 4\
**Last updated:** [November 18, 2018, 3:35pm UTC](https://discourse.julialang.org/t/incorrect-results-for-sinpi-and-cospi-when-using-fastmath-mode/17662 "2018-11-18T15:35:25Z")

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When firing up Julia with the --math-mode=fast option, I get incorrect results for sinpi and cospi functions. Is this a bug or am I missing something? With the default math mode: julia\> a = rand(5) 5-element Array{Floa…

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## [RigidBodyDynamics.jl attaching a new rigid body to the system](https://discourse.julialang.org/t/rigidbodydynamics-jl-attaching-a-new-rigid-body-to-the-system/17451)

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**Author:** [@phelipe](https://discourse.julialang.org/u/phelipe)\
**Replies:** 4\
**Last updated:** [November 18, 2018, 3:11pm UTC](https://discourse.julialang.org/t/rigidbodydynamics-jl-attaching-a-new-rigid-body-to-the-system/17451 "2018-11-18T15:11:35Z")

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Is it possible to add an extra load to a mechanism created from an urdf? For example, add a sphere to the last joint of a system. Can RigidBodyDynamics.attach! be used for this?

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## [read a .jxr file failed ](https://discourse.julialang.org/t/read-a-jxr-file-failed/17676)

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**Author:** [@zsz00](https://discourse.julialang.org/u/zsz00)\
**Replies:** 0\
**Last updated:** [November 18, 2018, 2:47pm UTC](https://discourse.julialang.org/t/read-a-jxr-file-failed/17676 "2018-11-18T14:47:38Z")

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read a .jxr file failed , what is wrong? using FileIO, ImageMagick; filename = "../test/matter/j0\_0.jxr" f1 = load(File(format"JXR", filename)) No FileIO.applicable\_loaders found for JXR

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## [\[ANN\] DandelionWebSockets.jl released for Julia 0.7 and 1.0](https://discourse.julialang.org/t/ann-dandelionwebsockets-jl-released-for-julia-0-7-and-1-0/17650)

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**Author:** [@erikedin](https://discourse.julialang.org/u/erikedin)\
**Replies:** 1\
**Last updated:** [November 18, 2018, 8:58am UTC](https://discourse.julialang.org/t/ann-dandelionwebsockets-jl-released-for-julia-0-7-and-1-0/17650 "2018-11-18T08:58:54Z")

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Hello! My WebSocket client DandelionWebSockets.jl is now released with v0.2.0, with Julia 0.7 and 1.0 compatibility. Some of the code was re-written and improved. The handshake code, which makes the connection, is stil…

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## [Multi-threading in Gurobi-JuMP Interface](https://discourse.julialang.org/t/multi-threading-in-gurobi-jump-interface/17626)

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**Author:** [@GabrielYin](https://discourse.julialang.org/u/GabrielYin)\
**Replies:** 4\
**Last updated:** [November 17, 2018, 11:46pm UTC](https://discourse.julialang.org/t/multi-threading-in-gurobi-jump-interface/17626 "2018-11-17T23:46:45Z")

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Hi there, I am a new Julia user in optimization usage, switched from GAMS and AMPL. I have tested some codes and they worked well. However, I would like to know how to set multi-threading in the Gurobi-JuMP interface. I…

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## [Discarding unused AffExpr](https://discourse.julialang.org/t/discarding-unused-affexpr/17634)

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**Author:** [@vtjeng](https://discourse.julialang.org/u/vtjeng)\
**Replies:** 1\
**Last updated:** [November 17, 2018, 3:44pm UTC](https://discourse.julialang.org/t/discarding-unused-affexpr/17634 "2018-11-17T15:44:31Z")

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As I’m creating my model in JuMP, I’m creating many AffExprs (~100k) but only a small fraction of them actually get used in constraints (I’m using interval arithmetic via ConditionalJuMP.jl to determine that the rest of …

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## [Trying to save a gif with Plots.jl results in an error](https://discourse.julialang.org/t/trying-to-save-a-gif-with-plots-jl-results-in-an-error/17620)

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**Author:** [@a-berg](https://discourse.julialang.org/u/a-berg)\
**Replies:** 1\
**Last updated:** [November 17, 2018, 10:37am UTC](https://discourse.julialang.org/t/trying-to-save-a-gif-with-plots-jl-results-in-an-error/17620 "2018-11-17T10:37:09Z")

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I’m not very experienced with julia yet and I wanted to create a gif for some animation. The animation is correctly created (using @animate macro) and I have manually checked that the 100 images are indeed created. How…

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## [Is anyone developing a SPA package like R/Shiny or Python/Dash?](https://discourse.julialang.org/t/is-anyone-developing-a-spa-package-like-r-shiny-or-python-dash/5733)

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**Author:** [@NickNack](https://discourse.julialang.org/u/NickNack)\
**Replies:** 28\
**Last updated:** [November 16, 2018, 9:09pm UTC](https://discourse.julialang.org/t/is-anyone-developing-a-spa-package-like-r-shiny-or-python-dash/5733 "2018-11-16T21:09:09Z")

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I’m working on a simple climate model that I would like to put online with some nice and friendly widgets. It would be a perfect fit for a Single Page Application, especially if Julia had a package that made this as simp…

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## [Multivariate logistic regression with interaction terms in Julia language](https://discourse.julialang.org/t/multivariate-logistic-regression-with-interaction-terms-in-julia-language/17611)

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**Author:** [@haley](https://discourse.julialang.org/u/haley)\
**Replies:** 1\
**Last updated:** [November 16, 2018, 9:04pm UTC](https://discourse.julialang.org/t/multivariate-logistic-regression-with-interaction-terms-in-julia-language/17611 "2018-11-16T21:04:22Z")

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Hello, I cannot find the answer to this question: Is is possible to learn logistic regression models of the form log(P / 1 - P) = a0 + a1 x1 + a2 x2 + a3 x3 + a12 x1 x2 + a13 x1 x3 + a23 x2 x3 + a123 x1 x2 x3? Thanks …

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## [Rotate a image](https://discourse.julialang.org/t/rotate-a-image/17586)

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**Author:** [@zsz00](https://discourse.julialang.org/u/zsz00)\
**Replies:** 10\
**Last updated:** [November 16, 2018, 4:03pm UTC](https://discourse.julialang.org/t/rotate-a-image/17586 "2018-11-16T16:03:05Z")

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I want to rotate a image with camara extri parameters matrix. but have error, can you help me amend it ? please!!! using Images, ImageFeatures, FileIO, ImageView using CoordinateTransformations, StaticArrays, Image…

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## [Odd slight perturbation in HypothesisTests](https://discourse.julialang.org/t/odd-slight-perturbation-in-hypothesistests/17582)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 5\
**Last updated:** [November 16, 2018, 3:42pm UTC](https://discourse.julialang.org/t/odd-slight-perturbation-in-hypothesistests/17582 "2018-11-16T15:42:22Z")

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julia\> using HypothesisTests, Random; julia\> Random.seed!(0); x= randn(100); y= randn(100); julia\> OneSampleTTest(x,y) the point estimate is slightly unstable. it may output one of the two: point estimate: …

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## [FWD: Request for Earth Science Informatics Proposals](https://discourse.julialang.org/t/fwd-request-for-earth-science-informatics-proposals/17591)

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**Author:** [@mauro3](https://discourse.julialang.org/u/mauro3)\
**Replies:** 0\
**Last updated:** [November 16, 2018, 8:17am UTC](https://discourse.julialang.org/t/fwd-request-for-earth-science-informatics-proposals/17591 "2018-11-16T08:17:31Z")

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Maybe of interest to someone here. I found an email advertising this in my inbox today (I’m in no way affiliated, I never even heard of them before): Request for Earth Science Informatics Incubator Proposals … projec…

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## [Strange behavior of \`mapreduce\`](https://discourse.julialang.org/t/strange-behavior-of-mapreduce/17588)

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**Author:** [@1115](https://discourse.julialang.org/u/1115)\
**Replies:** 2\
**Last updated:** [November 16, 2018, 7:49am UTC](https://discourse.julialang.org/t/strange-behavior-of-mapreduce/17588 "2018-11-16T07:49:11Z")

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I have a kernel, which uses the exp operation, it breaks down in a strange way Minimum working example: using CuArrays, CUDAnative CuArrays.allowscalar(false) x = randn(1000) |\> cu CUDAnative.map(CUDAnative.exp, x) CU…

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## [CUDAnative support for Float16](https://discourse.julialang.org/t/cudanative-support-for-float16/17369)

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**Author:** [@pedramz](https://discourse.julialang.org/u/pedramz)\
**Replies:** 5\
**Last updated:** [November 15, 2018, 10:19pm UTC](https://discourse.julialang.org/t/cudanative-support-for-float16/17369 "2018-11-15T22:19:44Z")

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I want to perform Float16 computation on GPU. In the vadd.jl example, when I change the rand function type from Float32 to Float16, the following error happens while running: ERROR: LoadError: InvalidIRError: compiling…

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## [How to time CUDA Event](https://discourse.julialang.org/t/how-to-time-cuda-event/17530)

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**Author:** [@cuchxq](https://discourse.julialang.org/u/cuchxq)\
**Replies:** 3\
**Last updated:** [November 15, 2018, 9:34pm UTC](https://discourse.julialang.org/t/how-to-time-cuda-event/17530 "2018-11-15T21:34:47Z")

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Hi, In CUDA C, you can time how long GPU ran by using event, this will record the time for just GPU running time, which does not include data transfer. Is there a similar functionality in CuArray or other GPU packages?

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## [Getting incremental cost for variables](https://discourse.julialang.org/t/getting-incremental-cost-for-variables/17563)

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**Author:** [@Rasoul](https://discourse.julialang.org/u/Rasoul)\
**Replies:** 1\
**Last updated:** [November 15, 2018, 4:09pm UTC](https://discourse.julialang.org/t/getting-incremental-cost-for-variables/17563 "2018-11-15T16:09:32Z")

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Can you please let me know how can I get incremental cost associated with variables after solving an optimization problem in Jump? Thanks in advance!

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## [Applicationerror: solver (gurobi) did not exit normally](https://discourse.julialang.org/t/applicationerror-solver-gurobi-did-not-exit-normally/17201)

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**Author:** [@Vondoe79](https://discourse.julialang.org/u/Vondoe79)\
**Replies:** 2\
**Last updated:** [November 14, 2018, 9:59pm UTC](https://discourse.julialang.org/t/applicationerror-solver-gurobi-did-not-exit-normally/17201 "2018-11-14T21:59:43Z")

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Hi there, I am getting this “applicationerror: solver (gurobi) did not exit normally”, the first time since using JuMP in 2 years. I have tried to look it up online, but no avail. Can anyone here please help me figure w…

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## [JuMP and user defined objective function: JuMPArray dimension problem](https://discourse.julialang.org/t/jump-and-user-defined-objective-function-jumparray-dimension-problem/17470)

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**Author:** [@axelle](https://discourse.julialang.org/u/axelle)\
**Replies:** 8\
**Last updated:** [November 14, 2018, 1:29pm UTC](https://discourse.julialang.org/t/jump-and-user-defined-objective-function-jumparray-dimension-problem/17470 "2018-11-14T13:29:37Z")

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Good afternoon, I had a look at previous topices on this subject and could not find the solution to my error. I have an optimization problem with a non linear user defined objective function called bk\_obj. This functio…

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## [cuArrays vs CUDANative](https://discourse.julialang.org/t/cuarrays-vs-cudanative/17504)

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**Author:** [@LaurentPlagne](https://discourse.julialang.org/u/LaurentPlagne)\
**Replies:** 3\
**Last updated:** [November 14, 2018, 12:38pm UTC](https://discourse.julialang.org/t/cuarrays-vs-cudanative/17504 "2018-11-14T12:38:01Z")

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Hi, From a 2D Array of floats b(nx,ny), I want to compute a(nx,ny-1) on the GPU as: function julia\_diff\_y(a,b) s=size(a) for j=1:s\[2\] for i=1:s\[1\] @inbounds a\[i,j\]=b\[i,j+1\]-b\[i,j\] en…

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## [Freeing memory in the GPU with CUDAdrv / CUDAnative / CuArrays](https://discourse.julialang.org/t/freeing-memory-in-the-gpu-with-cudadrv-cudanative-cuarrays/10946)

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**Author:** [@una-dinosauria](https://discourse.julialang.org/u/una-dinosauria)\
**Replies:** 8\
**Last updated:** [November 13, 2018, 7:28pm UTC](https://discourse.julialang.org/t/freeing-memory-in-the-gpu-with-cudadrv-cudanative-cuarrays/10946 "2018-11-13T19:28:43Z")

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I am writing some code that calls CUDA kernels via CUDAdrv, allocates some CuArrays and uses a generic matrix addition (which I think is done via CUDAnative). The problem I have is that after I call this code a couple o…

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## [Making a struct definition available on the cluster](https://discourse.julialang.org/t/making-a-struct-definition-available-on-the-cluster/17460)

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**Author:** [@rabarar](https://discourse.julialang.org/u/rabarar)\
**Replies:** 2\
**Last updated:** [November 13, 2018, 6:25pm UTC](https://discourse.julialang.org/t/making-a-struct-definition-available-on-the-cluster/17460 "2018-11-13T18:25:13Z")

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So I’m new to Julia - and I’ve been experimenting with the Distributed package - I wrote an example program to illustrate some of the concepts. Using remote channels, I can create primitive remote channel type, but how c…

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## [Flow "in" a Klein bottle](https://discourse.julialang.org/t/flow-in-a-klein-bottle/17475)

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**Author:** [@JeffreySarnoff](https://discourse.julialang.org/u/JeffreySarnoff)\
**Replies:** 3\
**Last updated:** [November 13, 2018, 6:07pm UTC](https://discourse.julialang.org/t/flow-in-a-klein-bottle/17475 "2018-11-13T18:07:04Z")

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Can we make something like this?

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## [GLPK + Homebrew erros - Not properly installed / Key "10.14" not found / Build errors](https://discourse.julialang.org/t/glpk-homebrew-erros-not-properly-installed-key-10-14-not-found-build-errors/17439)

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**Author:** [@miqlliot](https://discourse.julialang.org/u/miqlliot)\
**Replies:** 4\
**Last updated:** [November 13, 2018, 5:04pm UTC](https://discourse.julialang.org/t/glpk-homebrew-erros-not-properly-installed-key-10-14-not-found-build-errors/17439 "2018-11-13T17:04:23Z")

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Hi, I am using Julia for my Operations Research studies, but have struggled for over 3 months getting it running locally and have to use the online JuliaBox service. I have now managed to finally get the atom-integratio…

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## [Reinforcement learning with A\* and a deep heuristic](https://discourse.julialang.org/t/reinforcement-learning-with-a-and-a-deep-heuristic/17480)

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**Author:** [@skariel](https://discourse.julialang.org/u/skariel)\
**Replies:** 0\
**Last updated:** [November 13, 2018, 3:29pm UTC](https://discourse.julialang.org/t/reinforcement-learning-with-a-and-a-deep-heuristic/17480 "2018-11-13T15:29:17Z")

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100% Julia - see paper here: https://github.com/imagry/aleph\_star/blob/master/paper/aleph\_star.pdf and code here: https://github.com/imagry/aleph\_star now the real reason I’m writing this here is since I need help wi…

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## [\`scatter\` plots and marker colors -- change?](https://discourse.julialang.org/t/scatter-plots-and-marker-colors-change/17456)

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**Author:** [@BLI](https://discourse.julialang.org/u/BLI)\
**Replies:** 8\
**Last updated:** [November 13, 2018, 11:57am UTC](https://discourse.julialang.org/t/scatter-plots-and-marker-colors-change/17456 "2018-11-13T11:57:59Z")

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I get this strange warning when using scatter under Julia v. 1.0.2: julia\> scatter(rand(10)) 'c' argument looks like a single numeric RGB or RGBA sequence, which should be avoided as value-mapp ing will have precedence …

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## [SharedDict for multiple processes?](https://discourse.julialang.org/t/shareddict-for-multiple-processes/17447)

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**Author:** [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Replies:** 1\
**Last updated:** [November 12, 2018, 8:08pm UTC](https://discourse.julialang.org/t/shareddict-for-multiple-processes/17447 "2018-11-12T20:08:56Z")

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I am doing a bunch of distributed long calculations and I want to write results to a Dict. Is there a way for multiple Julia processes to share a Dict (with write access)? I don’t care if writing to the Dict in this wa…

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## [Alternative to DataFrame Readtable to read large data files with headers](https://discourse.julialang.org/t/alternative-to-dataframe-readtable-to-read-large-data-files-with-headers/15095)

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**Author:** [@astrowanders](https://discourse.julialang.org/u/astrowanders)\
**Replies:** 17\
**Last updated:** [November 12, 2018, 7:30pm UTC](https://discourse.julialang.org/t/alternative-to-dataframe-readtable-to-read-large-data-files-with-headers/15095 "2018-11-12T19:30:47Z")

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Hello! I’ve been using Julia to work with output from a stellar evolution code. My data files have several columns (~60 or more) and hundreds of rows. In previous versions of Julia, I used readtable in the DataFrame pac…

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