# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1574

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

**Page:** 1575

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## [Symbolic spectra radius of matrix?](https://discourse.julialang.org/t/symbolic-spectra-radius-of-matrix/50058)

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**Author:** [@BLI](https://discourse.julialang.org/u/BLI)\
**Replies:** 8\
**Last updated:** [November 13, 2020, 8:05am UTC](https://discourse.julialang.org/t/symbolic-spectra-radius-of-matrix/50058 "2020-11-13T08:05:02Z")

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I’m looking for the spectral radius of matrix M given by: M =\\left(\\begin{array}{ccc}0 & k & r\\\\1 & 0 & 0\\\\0 & 1-n & 0\\end{array}\\right) where all of k,r,n are non-negative reals. WolframAlpha can compute the eigenva…

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## [Saving Probabilities in Log Domain (Constructor Issues)](https://discourse.julialang.org/t/saving-probabilities-in-log-domain-constructor-issues/49968)

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**Author:** [@rakeshvar](https://discourse.julialang.org/u/rakeshvar)\
**Replies:** 6\
**Last updated:** [November 13, 2020, 8:01am UTC](https://discourse.julialang.org/t/saving-probabilities-in-log-domain-constructor-issues/49968 "2020-11-13T08:01:35Z")

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I am working with probabilities that can get really low. So I am going to (optionally) store them in log domain and operate there. I do not want my function code to change whether I am using log domain or not. Note that …

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## [Operation on columns of a matrix](https://discourse.julialang.org/t/operation-on-columns-of-a-matrix/50060)

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**Author:** [@nhavt](https://discourse.julialang.org/u/nhavt)\
**Replies:** 3\
**Last updated:** [November 13, 2020, 7:51am UTC](https://discourse.julialang.org/t/operation-on-columns-of-a-matrix/50060 "2020-11-13T07:51:45Z")

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Hello there, I would like to ask a question regarding an operation on two columns of a matrix as you can see below. Here I proposed two functions to perform the task. The function f1 has two allocations even though I us…

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## [Advice for package naming](https://discourse.julialang.org/t/advice-for-package-naming/50073)

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**Author:** [@Azzaare](https://discourse.julialang.org/u/Azzaare)\
**Replies:** 5\
**Last updated:** [November 13, 2020, 6:42am UTC](https://discourse.julialang.org/t/advice-for-package-naming/50073 "2020-11-13T06:42:59Z")

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Hi there! I am working on a package for different Constraint-Based Local Search (CBLS) Solvers. I am a bit at a loss on how to name it. CBLS.jl is hard to understand outside of the community. Same for CBLSSolvers.jl C…

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## [Vectorized updating operator?](https://discourse.julialang.org/t/vectorized-updating-operator/50079)

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**Author:** [@Lincoln\_Hannah](https://discourse.julialang.org/u/Lincoln_Hannah)\
**Replies:** 3\
**Last updated:** [November 13, 2020, 6:29am UTC](https://discourse.julialang.org/t/vectorized-updating-operator/50079 "2020-11-13T06:29:12Z")

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Is it possible to vectorize an updating operator? This gives an error a,b,c = (10,20,30) a,b,c ./=10

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## [Specifying a set of algorithms](https://discourse.julialang.org/t/specifying-a-set-of-algorithms/50061)

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**Author:** [@dpsanders](https://discourse.julialang.org/u/dpsanders)\
**Replies:** 14\
**Last updated:** [November 13, 2020, 6:06am UTC](https://discourse.julialang.org/t/specifying-a-set-of-algorithms/50061 "2020-11-13T06:06:18Z")

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Suppose I have a function f and I need to specify which algorithms to use inside f (e.g. different optimization methods to combine together). What is the best (i.e. most performant) way to do that? MWE: A(x) = 2x B(x)…

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## [How would one interop with cpp?](https://discourse.julialang.org/t/how-would-one-interop-with-cpp/49733)

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**Author:** [@s-kap](https://discourse.julialang.org/u/s-kap)\
**Replies:** 7\
**Last updated:** [November 13, 2020, 4:51am UTC](https://discourse.julialang.org/t/how-would-one-interop-with-cpp/49733 "2020-11-13T04:51:14Z")

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Hey folks, I’d like to use the cpp lib for apache arrow but I’m having a tough time with it. For some context, I’m aware that there is an Arrow.jl package however that only supports the memory format. The cpp lib is ve…

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## [\[ANN\] GADM.jl](https://discourse.julialang.org/t/ann-gadm-jl/50057)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 2\
**Last updated:** [November 13, 2020, 1:50am UTC](https://discourse.julialang.org/t/ann-gadm-jl/50057 "2020-11-13T01:50:04Z")

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I would like to publicly thank Aayush Joglekar (@zerefwayne) for his amazing work on a new awesome package GADM.jl :tada: The package was written as part of the MLH fellowship program, and I am really happy that I had th…

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## [Solve minimization problem where constraint is the system of linear inequation with MathOptInterface efficiently](https://discourse.julialang.org/t/solve-minimization-problem-where-constraint-is-the-system-of-linear-inequation-with-mathoptinterface-efficiently/23571)

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**Author:** [@Yuya-Furusawa](https://discourse.julialang.org/u/Yuya-Furusawa)\
**Replies:** 11\
**Last updated:** [November 12, 2020, 10:29pm UTC](https://discourse.julialang.org/t/solve-minimization-problem-where-constraint-is-the-system-of-linear-inequation-with-mathoptinterface-efficiently/23571 "2020-11-12T22:29:21Z")

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I want to solve min cx s.t. Ax + b \< 0 with MathOptInterface, where A is a matrix and b and c are vectors. However, I couldn’t understand the documentation of MathOptInterface. Currently, my code is as follows: (No…

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## [\[ANN\] Javis.jl v0.3](https://discourse.julialang.org/t/ann-javis-jl-v0-3/49972)

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**Author:** [@Wikunia](https://discourse.julialang.org/u/Wikunia)\
**Replies:** 5\
**Last updated:** [November 12, 2020, 7:55pm UTC](https://discourse.julialang.org/t/ann-javis-jl-v0-3/49972 "2020-11-12T19:55:56Z")

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Javis Is Better Than Ever! :tada: It is with great excitement that we announce the release of Javis v0.3.0! :tada: :tada: This release was focused on adding in some much desired features as well as a rethink of its synt…

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## [ERROR: MethodError: no method matching decompose()](https://discourse.julialang.org/t/error-methoderror-no-method-matching-decompose/49904)

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**Author:** [@stefkuypers](https://discourse.julialang.org/u/stefkuypers)\
**Replies:** 9\
**Last updated:** [November 12, 2020, 7:35pm UTC](https://discourse.julialang.org/t/error-methoderror-no-method-matching-decompose/49904 "2020-11-12T19:35:35Z")

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Hi, I have defined the following types: struct Percentage \<: Real value::Float64 Percentage(x) = x \< 0 ? new(0) : x \> 1 ? new(1) : new(round(x, digits = 6)) end Base.show(io::IO, x::Percentage) = print(io, "$(…

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## [ERROR: GitError(Code:ERROR, Class:Submodule, cannot get submodules without a working tree)](https://discourse.julialang.org/t/error-giterror-code-error-class-submodule-cannot-get-submodules-without-a-working-tree/49926)

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**Author:** [@mleprovost](https://discourse.julialang.org/u/mleprovost)\
**Replies:** 6\
**Last updated:** [November 12, 2020, 7:16pm UTC](https://discourse.julialang.org/t/error-giterror-code-error-class-submodule-cannot-get-submodules-without-a-working-tree/49926 "2020-11-12T19:16:57Z")

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Hello, I would like to add one of my package AdaptiveTransportMap to a project but I get the following error message: (NlVortexAssim) pkg\> add AdaptiveTransportMap/ Updating git-repo \`/media/mat/HDD/AdaptiveTranspor…

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## [Conversion of Vector{UInt8} to String without copy](https://discourse.julialang.org/t/conversion-of-vector-uint8-to-string-without-copy/49837)

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**Author:** [@JuergenD](https://discourse.julialang.org/u/JuergenD)\
**Replies:** 7\
**Last updated:** [November 12, 2020, 6:32pm UTC](https://discourse.julialang.org/t/conversion-of-vector-uint8-to-string-without-copy/49837 "2020-11-12T18:32:03Z")

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Hi, use case: large files with a binary structure and embedded “text” elements. Depending on the file size, we either read them fully into mem, or mmap them. Hence in both cases, the data are fully available in memory…

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## [Operation on an RObject{RealSxp} Created Using RCall](https://discourse.julialang.org/t/operation-on-an-robject-realsxp-created-using-rcall/50059)

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**Author:** [@atparedes](https://discourse.julialang.org/u/atparedes)\
**Replies:** 1\
**Last updated:** [November 12, 2020, 5:27pm UTC](https://discourse.julialang.org/t/operation-on-an-robject-realsxp-created-using-rcall/50059 "2020-11-12T17:27:45Z")

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Hello All, New to Julia: I am using Julia to develop a large Monte Carlo simulation investigating the robustness of several statistical procedures. I created a couple of variables (vector) from the skew-normal distribut…

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## [Precompilation error with Julia 1.5.3 (Windows 10 64-bit)](https://discourse.julialang.org/t/precompilation-error-with-julia-1-5-3-windows-10-64-bit/50028)

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**Author:** [@sambitdash](https://discourse.julialang.org/u/sambitdash)\
**Replies:** 7\
**Last updated:** [November 12, 2020, 4:08pm UTC](https://discourse.julialang.org/t/precompilation-error-with-julia-1-5-3-windows-10-64-bit/50028 "2020-11-12T16:08:22Z")

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Hi All, Is anyone else facing the same issue as well? I had installation of Julia 1.5.2 earlier. And was using packages like IJulia. Now I installed Julia 1.5.3. When I lauch Julia 1.5.3 and type using IJulia I see the …

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## [Can't use clipboard() out REPL](https://discourse.julialang.org/t/cant-use-clipboard-out-repl/50055)

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**Author:** [@paulowagner1985](https://discourse.julialang.org/u/paulowagner1985)\
**Replies:** 2\
**Last updated:** [November 12, 2020, 4:06pm UTC](https://discourse.julialang.org/t/cant-use-clipboard-out-repl/50055 "2020-11-12T16:06:02Z")

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Hey guys! I’m having problems using clipboard() outside of the REPL… If i make a clip.jl file with: x = “hi” clipboard(x) I get the message: ERROR LoadError: UndefVarError: clipboard not defined Also with only cl…

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## [How to make top title in group layout plot?](https://discourse.julialang.org/t/how-to-make-top-title-in-group-layout-plot/50046)

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**Author:** [@Ahmed\_Salih](https://discourse.julialang.org/u/Ahmed_Salih)\
**Replies:** 2\
**Last updated:** [November 12, 2020, 3:28pm UTC](https://discourse.julialang.org/t/how-to-make-top-title-in-group-layout-plot/50046 "2020-11-12T15:28:25Z")

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Hello! I have this plot: How would I make a title above both of them called “My Plot”? These are the basic commands I use: l = @layout grid(2,1) pall = plot(p1,p2, layout = l,size=(800,800)) If I try using the “…

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## [Run(cmd) manual examples throw error](https://discourse.julialang.org/t/run-cmd-manual-examples-throw-error/49916)

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**Author:** [@Derek\_Vetsch](https://discourse.julialang.org/u/Derek_Vetsch)\
**Replies:** 6\
**Last updated:** [November 12, 2020, 3:25pm UTC](https://discourse.julialang.org/t/run-cmd-manual-examples-throw-error/49916 "2020-11-12T15:25:50Z")

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In the examples from the manual section “Running External Programs”, I can’t seem to get the examples to work on my machine… cmd = \`echo hello\` run(cmd) Here is the error: ERROR: IOError: could not spawn \`echo hello\`:…

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## [Testing return types of functions](https://discourse.julialang.org/t/testing-return-types-of-functions/50049)

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**Author:** [@wulpuqu](https://discourse.julialang.org/u/wulpuqu)\
**Replies:** 2\
**Last updated:** [November 12, 2020, 2:41pm UTC](https://discourse.julialang.org/t/testing-return-types-of-functions/50049 "2020-11-12T14:41:41Z")

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Hello everyone, Given a function definition like g(varargs...)::T2 = ... Is there a way to retrieve the return type T2 without evaluating typeof(g(varargs...)) ? I would like to test if a function is returning an agg…

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## [@eval with Observable in Interact](https://discourse.julialang.org/t/eval-with-observable-in-interact/50054)

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**Author:** [@hagi](https://discourse.julialang.org/u/hagi)\
**Replies:** 0\
**Last updated:** [November 12, 2020, 2:58pm UTC](https://discourse.julialang.org/t/eval-with-observable-in-interact/50054 "2020-11-12T14:58:02Z")

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Hi, I have a problem with Interact, where I don’t understand what is wrong. I have the following MWE. I have a csv file with several columns that might look like this: Result,A\_Result,B\_Result,C\_Result 10,1,3,4 12,3,…

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## [Convex DCP rules](https://discourse.julialang.org/t/convex-dcp-rules/50027)

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**Author:** [@faisal\_moh](https://discourse.julialang.org/u/faisal_moh)\
**Replies:** 1\
**Last updated:** [November 12, 2020, 1:52pm UTC](https://discourse.julialang.org/t/convex-dcp-rules/50027 "2020-11-12T13:52:00Z")

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Hi, I’m new to Julia and reviewing the convex package. I provided the objective function of max(100a + 150b), constrained to b \<= 99 and 372a^2 + 55b^2 \<= 628. This is the simplified formulation of my actual objective …

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## [Modelling a NeuralODE with external excitation using DiffEqFlux.jl](https://discourse.julialang.org/t/modelling-a-neuralode-with-external-excitation-using-diffeqflux-jl/50045)

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**Author:** [@Gregor](https://discourse.julialang.org/u/Gregor)\
**Replies:** 1\
**Last updated:** [November 12, 2020, 1:03pm UTC](https://discourse.julialang.org/t/modelling-a-neuralode-with-external-excitation-using-diffeqflux-jl/50045 "2020-11-12T13:03:06Z")

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Hello everyone, following this (DiffEqFlux.jl – A Julia Library for Neural Differential Equations) introduction to DiffEqFlux.jl I’ve set up a slightly modified example (I’m using a different diff. equation). My code wo…

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## [Standard way to get first element of iterator satisfying predicate](https://discourse.julialang.org/t/standard-way-to-get-first-element-of-iterator-satisfying-predicate/25038)

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**Author:** [@zardav](https://discourse.julialang.org/u/zardav)\
**Replies:** 12\
**Last updated:** [November 12, 2020, 12:02pm UTC](https://discourse.julialang.org/t/standard-way-to-get-first-element-of-iterator-satisfying-predicate/25038 "2020-11-12T12:02:54Z")

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I have a collection and want to get the first element satisfying predicate p. One way I can achieve it is first(x for x in col if p(x)) but I thought maybe there is more standard way, something such first(p, col). What…

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## [Best way for comparisons in one line to avoid undesired effects of operator precedence](https://discourse.julialang.org/t/best-way-for-comparisons-in-one-line-to-avoid-undesired-effects-of-operator-precedence/49973)

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**Author:** [@GerhardTotschnig](https://discourse.julialang.org/u/GerhardTotschnig)\
**Replies:** 5\
**Last updated:** [November 12, 2020, 11:53am UTC](https://discourse.julialang.org/t/best-way-for-comparisons-in-one-line-to-avoid-undesired-effects-of-operator-precedence/49973 "2020-11-12T11:53:23Z")

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I am wondering how to write best a simple if comparison expression else expression end in one line. julia\> if 7+2\<10 3 else 0 end 3 works as desired. If the comparison is true, give a value 3 else give …

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## [How to get in XLSX.jl a XLSX.CellRef from column and row number](https://discourse.julialang.org/t/how-to-get-in-xlsx-jl-a-xlsx-cellref-from-column-and-row-number/48752)

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**Author:** [@GerhardTotschnig](https://discourse.julialang.org/u/GerhardTotschnig)\
**Replies:** 3\
**Last updated:** [November 11, 2020, 10:47am UTC](https://discourse.julialang.org/t/how-to-get-in-xlsx-jl-a-xlsx-cellref-from-column-and-row-number/48752 "2020-11-11T10:47:01Z")

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I have a Question regarding XLSX.jl: One can insert a 2 dimensional data matrix MA via, XLSX.openxlsx("my\_Test.xlsx", mode="rw") do xf sheet = xf\[1\] sheet\["C7"\] = MA end but if I want to add this matrix in col…

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## [Plot doesn't work, doesn't display in the pane in Atom](https://discourse.julialang.org/t/plot-doesnt-work-doesnt-display-in-the-pane-in-atom/50007)

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**Author:** [@Dailysight](https://discourse.julialang.org/u/Dailysight)\
**Replies:** 2\
**Last updated:** [November 12, 2020, 10:38am UTC](https://discourse.julialang.org/t/plot-doesnt-work-doesnt-display-in-the-pane-in-atom/50007 "2020-11-12T10:38:40Z")

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Hey everyone ! It’s my first topic on this forum and i’m here to ask a little question about the use of plot. I have done the following code to display a landmark in 3D. But when i call the function “affichage\_R”, nothi…

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## [Using Generalized Likelihood with one dimesional time series as data in DifferentialEquations.jl](https://discourse.julialang.org/t/using-generalized-likelihood-with-one-dimesional-time-series-as-data-in-differentialequations-jl/49989)

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**Author:** [@claudio20497](https://discourse.julialang.org/u/claudio20497)\
**Replies:** 1\
**Last updated:** [November 12, 2020, 10:20am UTC](https://discourse.julialang.org/t/using-generalized-likelihood-with-one-dimesional-time-series-as-data-in-differentialequations-jl/49989 "2020-11-12T10:20:36Z")

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I anticipate that this question could be down to my ignorance in statistics. I’m trying to apply the DifferentialEquations.jl tutorial on how to use Generalized Likelihood to a particular case in which the data is a one…

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## [Converting well structure VBA code, with multiple sub-routine call, to Julia](https://discourse.julialang.org/t/converting-well-structure-vba-code-with-multiple-sub-routine-call-to-julia/50031)

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**Author:** [@Peter-Jolly](https://discourse.julialang.org/u/Peter-Jolly)\
**Replies:** 4\
**Last updated:** [November 12, 2020, 10:17am UTC](https://discourse.julialang.org/t/converting-well-structure-vba-code-with-multiple-sub-routine-call-to-julia/50031 "2020-11-12T10:17:18Z")

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I have been using Julia for about a week using Vscode as my IDE. Simple examples not problems. My task at hand it to convert well structure code (in VBA) to Julia - I am solving a system of 130 ODE’s (initial value probl…

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## [Using Julia to extract information from a ballot](https://discourse.julialang.org/t/using-julia-to-extract-information-from-a-ballot/47239)

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**Author:** [@Nosferican](https://discourse.julialang.org/u/Nosferican)\
**Replies:** 7\
**Last updated:** [November 12, 2020, 10:14am UTC](https://discourse.julialang.org/t/using-julia-to-extract-information-from-a-ballot/47239 "2020-11-12T10:14:13Z")

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I would like to identify tools in the Julia ecosystem to parse a model ballot. For example, from the following PDF, obtain Candidature Candidate’s name Party Affiliation

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## [Flux Pendulum DDPG example fails on GPU](https://discourse.julialang.org/t/flux-pendulum-ddpg-example-fails-on-gpu/49975)

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**Author:** [@lilanger](https://discourse.julialang.org/u/lilanger)\
**Replies:** 2\
**Last updated:** [November 12, 2020, 9:52am UTC](https://discourse.julialang.org/t/flux-pendulum-ddpg-example-fails-on-gpu/49975 "2020-11-12T09:52:55Z")

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I am pretty new to Flux and try to get the Pendulum environment (using a slightly modified Reinforce.jl environment: Pendulum update) running with DDPG with newer package versions (based on Flux model-zoo). It seems to …

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