# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1216

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

**Page:** 1217

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## [How to convert a matrix to an RGB image using Images.jl?](https://discourse.julialang.org/t/how-to-convert-a-matrix-to-an-rgb-image-using-images-jl/7265)

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**Author:** [@robblackwell](https://discourse.julialang.org/u/robblackwell)\
**Replies:** 16\
**Last updated:** [November 5, 2021, 9:31am UTC](https://discourse.julialang.org/t/how-to-convert-a-matrix-to-an-rgb-image-using-images-jl/7265 "2021-11-05T09:31:33Z")

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Let’s say that I have a matrix x x = \[0 0.5 1; 0.6 0.7 08.; 1 0.1 0.2\] I can display it as a grayscale image using Gray.(x) How can I convert it to an RGB image using a specified color gradient? Plots.jl allows me t…

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## [Trying to figure out parametric dispach](https://discourse.julialang.org/t/trying-to-figure-out-parametric-dispach/70860)

<div class="topic-metadata">

**Author:** [@dodoplus](https://discourse.julialang.org/u/dodoplus)\
**Replies:** 2\
**Last updated:** [November 5, 2021, 9:15am UTC](https://discourse.julialang.org/t/trying-to-figure-out-parametric-dispach/70860 "2021-11-05T09:15:04Z")

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Hi, The following code: abstract type XX{A \<: Real} end function makexx(T::Type{\<:XX}) T(6.0) end struct X1{A} \<: XX{A} x::A end struct X2{A} \<: XX{A} end X1() = makexx(X1) X1() Crashes with: MethodError: n…

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## [About the installation setting and test with simple plot script](https://discourse.julialang.org/t/about-the-installation-setting-and-test-with-simple-plot-script/70987)

<div class="topic-metadata">

**Author:** [@Jeongwon](https://discourse.julialang.org/u/Jeongwon)\
**Replies:** 0\
**Last updated:** [November 5, 2021, 4:59am UTC](https://discourse.julialang.org/t/about-the-installation-setting-and-test-with-simple-plot-script/70987 "2021-11-05T04:59:58Z")

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I just installed Julia and Atom and tried simple plot with “Pyplot” but the error messages came out starting with below and Julia had exited. Am I in trouble with a compatibility? Julia version 1.6.3, Atom version 1.58.…

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## [Where is the extra memory allocation?](https://discourse.julialang.org/t/where-is-the-extra-memory-allocation/70866)

<div class="topic-metadata">

**Author:** [@maphdze](https://discourse.julialang.org/u/maphdze)\
**Replies:** 11\
**Last updated:** [November 5, 2021, 1:49am UTC](https://discourse.julialang.org/t/where-is-the-extra-memory-allocation/70866 "2021-11-05T01:49:23Z")

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I wrote a program several days ago, and the memory allocation is acceptable (2.79k allocations: 124.820MiB). Today, I add some new functions in it to implenment another feature. Then the memory allocation becomes much bi…

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## [Using IJulia with existing Jupyter installation outwith Anaconda](https://discourse.julialang.org/t/using-ijulia-with-existing-jupyter-installation-outwith-anaconda/38832)

<div class="topic-metadata">

**Author:** [@justinwalker](https://discourse.julialang.org/u/justinwalker)\
**Replies:** 15\
**Last updated:** [November 5, 2021, 1:43am UTC](https://discourse.julialang.org/t/using-ijulia-with-existing-jupyter-installation-outwith-anaconda/38832 "2021-11-05T01:43:20Z")

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I installed Julia today and then tried to connect to my existing Jupyter installation; note that I don’t have, or wish to have Anaconda installed. The IJulia package adds and builds successfully but the ENV is missing an…

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## [Finite element method interpolation performance](https://discourse.julialang.org/t/finite-element-method-interpolation-performance/70944)

<div class="topic-metadata">

**Author:** [@maphdze](https://discourse.julialang.org/u/maphdze)\
**Replies:** 3\
**Last updated:** [November 5, 2021, 12:52am UTC](https://discourse.julialang.org/t/finite-element-method-interpolation-performance/70944 "2021-11-05T00:52:26Z")

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I have a question about the performance in interpolation in finite element method. In the Official Document, it is suggested to do small size array operations with StaticArrays.jl. In my finite element program, the glo…

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## [AmplNLWriter no longer works with JuMP](https://discourse.julialang.org/t/amplnlwriter-no-longer-works-with-jump/70740)

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**Author:** [@optimist](https://discourse.julialang.org/u/optimist)\
**Replies:** 10\
**Last updated:** [November 4, 2021, 11:52pm UTC](https://discourse.julialang.org/t/amplnlwriter-no-longer-works-with-jump/70740 "2021-11-04T23:52:11Z")

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I was using AmplNLWriter with Ipopt\_jll, but it stopped working when I installed MadNLP. I have removed all my packages and reinstalled (excluding MaNLP), but I have not been able to make AmplNLWriter to work. The error …

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## [Problem passing gradients into Optim](https://discourse.julialang.org/t/problem-passing-gradients-into-optim/70885)

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**Author:** [@jmcastro2109](https://discourse.julialang.org/u/jmcastro2109)\
**Replies:** 4\
**Last updated:** [November 4, 2021, 11:14pm UTC](https://discourse.julialang.org/t/problem-passing-gradients-into-optim/70885 "2021-11-04T23:14:21Z")

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Hi! I am trying to minimize a likelihood function for a large number of parameters. Since, the problem is quite large it would be very useful to pass the analytical gradients and the Hessian into the optimization problem…

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## [ArrayInterface not available on Storage Server?](https://discourse.julialang.org/t/arrayinterface-not-available-on-storage-server/70973)

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**Author:** [@Samuel\_Stapleton](https://discourse.julialang.org/u/Samuel_Stapleton)\
**Replies:** 1\
**Last updated:** [November 4, 2021, 11:14pm UTC](https://discourse.julialang.org/t/arrayinterface-not-available-on-storage-server/70973 "2021-11-04T23:14:07Z")

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I am unable to fetch the latest version of ArrayInterface (3.1.40) from the us-east storage server: https://us-east.storage.juliahub.com/package/4fba245c-0d91-5ea0-9b3e-6abc04ee57a9/e527b258413e0c6d4f66ade574744c94edef8…

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## [Fitting a polynomial of degree 10 to data](https://discourse.julialang.org/t/fitting-a-polynomial-of-degree-10-to-data/70924)

<div class="topic-metadata">

**Author:** [@valperez](https://discourse.julialang.org/u/valperez)\
**Replies:** 9\
**Last updated:** [November 4, 2021, 6:27pm UTC](https://discourse.julialang.org/t/fitting-a-polynomial-of-degree-10-to-data/70924 "2021-11-04T18:27:35Z")

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Hi there :slight\_smile: I’m trying to test Julia’s accuracy so I’m trying to fit a polynomial of degree 10 to my data. The data can be found in the following link: https://www.itl.nist.gov/div898/strd/lls/data/LINKS/DAT…

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## [Too much matrix inverse error?](https://discourse.julialang.org/t/too-much-matrix-inverse-error/70974)

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**Author:** [@zhangjin](https://discourse.julialang.org/u/zhangjin)\
**Replies:** 3\
**Last updated:** [November 4, 2021, 8:40pm UTC](https://discourse.julialang.org/t/too-much-matrix-inverse-error/70974 "2021-11-04T20:40:30Z")

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I use the inv() to do the inverse of the matrix, but I find that I don’t get the inverse matrix, or is it due to too much error? This is my matrix , but inv(M1)\*M1 not equal to unit matrix, Why is it happen?

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## [Length and setting of ticks](https://discourse.julialang.org/t/length-and-setting-of-ticks/70952)

<div class="topic-metadata">

**Author:** [@mixstam1453](https://discourse.julialang.org/u/mixstam1453)\
**Replies:** 2\
**Last updated:** [November 4, 2021, 7:52pm UTC](https://discourse.julialang.org/t/length-and-setting-of-ticks/70952 "2021-11-04T19:52:35Z")

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hello, i am new in Plots.jl and i would like to put ticks in all my axis of the plot with framestyle=:box . Here is my code with the default function: x = 0:0.1:2pi ; y1 = cos.(x) default(fontfamily ="New Century Scho…

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## [Broadcasting over a Flux.DataLoader](https://discourse.julialang.org/t/broadcasting-over-a-flux-dataloader/70414)

<div class="topic-metadata">

**Author:** [@austinbean](https://discourse.julialang.org/u/austinbean)\
**Replies:** 11\
**Last updated:** [November 4, 2021, 6:59pm UTC](https://discourse.julialang.org/t/broadcasting-over-a-flux-dataloader/70414 "2021-11-04T18:59:00Z")

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Apologies for this question since I’ve had a lot of trouble producing a MWE (which I don’t have). I’m working on an RNN using text data (each observation is a sentence - each word in each sentence is mapped to a word em…

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## [Trying to write a simple sampling function](https://discourse.julialang.org/t/trying-to-write-a-simple-sampling-function/70932)

<div class="topic-metadata">

**Author:** [@Canaan\_Breiss](https://discourse.julialang.org/u/Canaan_Breiss)\
**Replies:** 6\
**Last updated:** [November 4, 2021, 6:11pm UTC](https://discourse.julialang.org/t/trying-to-write-a-simple-sampling-function/70932 "2021-11-04T18:11:15Z")

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Hi folks! I have what (I think) is an extremely basic question, and I’m not quite sure where to start. I’m moderately proficient in python and R, but have never used Julia before. I’m trying to make a simple function th…

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## [Slicing Custom Indexes](https://discourse.julialang.org/t/slicing-custom-indexes/70933)

<div class="topic-metadata">

**Author:** [@andrew-saydjari](https://discourse.julialang.org/u/andrew-saydjari)\
**Replies:** 5\
**Last updated:** [November 4, 2021, 6:07pm UTC](https://discourse.julialang.org/t/slicing-custom-indexes/70933 "2021-11-04T18:07:21Z")

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I am trying to write a custom indexed array (with reflective boundary conditions). I would really like to be able to slice the array in the same way that the amazing developers of ShiftedArrays did. x = reshape(1:100,10…

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## [How to improve the speed of "inpolygon"?](https://discourse.julialang.org/t/how-to-improve-the-speed-of-inpolygon/70969)

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**Author:** [@leon](https://discourse.julialang.org/u/leon)\
**Replies:** 5\
**Last updated:** [November 4, 2021, 6:03pm UTC](https://discourse.julialang.org/t/how-to-improve-the-speed-of-inpolygon/70969 "2021-11-04T18:03:55Z")

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I have about 30,000 pairs of longitude and latitude data (lon1 and lon2). My goal is to check if they will fall into a polygon defined by (lonW and latW). In Matlab, I can do this as below. It is blazing fast. It litera…

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## [Use function argument inside optional (default) arguments type specification](https://discourse.julialang.org/t/use-function-argument-inside-optional-default-arguments-type-specification/70963)

<div class="topic-metadata">

**Author:** [@claudio20497](https://discourse.julialang.org/u/claudio20497)\
**Replies:** 2\
**Last updated:** [November 4, 2021, 5:16pm UTC](https://discourse.julialang.org/t/use-function-argument-inside-optional-default-arguments-type-specification/70963 "2021-11-04T17:16:05Z")

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Hi, I encountered the following behaviour. I can use a function’s arguments to set the default values for optional (default) arguments: julia\> f(a::Int64; b::Int64 = a-1 ) = b f (generic function with 1 method) But I …

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## [\[ANN\] OpenTelemetry.jl - Now it's time to improve the observability of your system](https://discourse.julialang.org/t/ann-opentelemetry-jl-now-its-time-to-improve-the-observability-of-your-system/70901)

<div class="topic-metadata">

**Author:** [@findmyway](https://discourse.julialang.org/u/findmyway)\
**Replies:** 1\
**Last updated:** [November 4, 2021, 5:05pm UTC](https://discourse.julialang.org/t/ann-opentelemetry-jl-now-its-time-to-improve-the-observability-of-your-system/70901 "2021-11-04T17:05:14Z")

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What is OpenTelemetry.jl ? OpenTelemetry.jl is a Julia implementation of the OpenTelemetry Specification. It provides a set of unified interfaces to create and collect telemetry data (like traces, metrics, and logs) from…

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## [Shared memory computation inside of each task of parallel map](https://discourse.julialang.org/t/shared-memory-computation-inside-of-each-task-of-parallel-map/70927)

<div class="topic-metadata">

**Author:** [@tictaccat](https://discourse.julialang.org/u/tictaccat)\
**Replies:** 5\
**Last updated:** [November 4, 2021, 5:01pm UTC](https://discourse.julialang.org/t/shared-memory-computation-inside-of-each-task-of-parallel-map/70927 "2021-11-04T17:01:10Z")

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Hi! I have a pretty simple problem: I have about 50 tasks I would like to do simultaneously, and I would like to do exploit shared memory parallelism on each task. I have control of about 50 nodes with about 40 CPUs eac…

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## [How to construct a large sparse matrix?](https://discourse.julialang.org/t/how-to-construct-a-large-sparse-matrix/7241)

<div class="topic-metadata">

**Author:** [@onetonfoot](https://discourse.julialang.org/u/onetonfoot)\
**Replies:** 6\
**Last updated:** [November 4, 2021, 4:58pm UTC](https://discourse.julialang.org/t/how-to-construct-a-large-sparse-matrix/7241 "2021-11-04T16:58:20Z")

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Currently, I’m using n = 10^5 M = sparse(BitArray(n,n)) But when n \> 10^6 I run out of memory so this doesn’t work. I’m unsure what to do as the bellow syntax chucks an error SparseMatrixCSC{Bool}(n,n) MethodError: no…

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## [PyError pyeval.jl not found](https://discourse.julialang.org/t/pyerror-pyeval-jl-not-found/70813)

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**Author:** [@max\_schwarzer](https://discourse.julialang.org/u/max_schwarzer)\
**Replies:** 2\
**Last updated:** [November 4, 2021, 4:29pm UTC](https://discourse.julialang.org/t/pyerror-pyeval-jl-not-found/70813 "2021-11-04T16:29:38Z")

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I am using Anaconda and when trying to use PyCall in Julia I get the following error: ERROR: PyError ($(Expr(:escape, :(ccall(#= C:\\Users\\mschwarz.julia\\packages\\PyCall\\BD546\\src\\pyeval.jl:38 =# @pysym(:PyEval\_EvalCode…

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## [Julia Ecosystem Engineer at RelationalAI](https://discourse.julialang.org/t/julia-ecosystem-engineer-at-relationalai/70916)

<div class="topic-metadata">

**Author:** [@sacha](https://discourse.julialang.org/u/sacha)\
**Replies:** 0\
**Last updated:** [November 3, 2021, 9:20pm UTC](https://discourse.julialang.org/t/julia-ecosystem-engineer-at-relationalai/70916 "2021-11-03T21:20:32Z")

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Please see https://www.relational.ai/job-julia-ecosystem-engineer for more information and to apply. Thanks and best wishes!

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## [How to use the Windows API for Desktop Duplication API?](https://discourse.julialang.org/t/how-to-use-the-windows-api-for-desktop-duplication-api/70962)

<div class="topic-metadata">

**Author:** [@Pytrator](https://discourse.julialang.org/u/Pytrator)\
**Replies:** 0\
**Last updated:** [November 4, 2021, 3:50pm UTC](https://discourse.julialang.org/t/how-to-use-the-windows-api-for-desktop-duplication-api/70962 "2021-11-04T15:50:32Z")

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Hey there! I try to get as many frames of my desktop as possible. The Windows desktop API appears to be a good solution to get that. However, I don’t know how to do it. I now get things done when it’s documented for C …

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## [Simple type problem](https://discourse.julialang.org/t/simple-type-problem/70958)

<div class="topic-metadata">

**Author:** [@Igor\_Douven](https://discourse.julialang.org/u/Igor_Douven)\
**Replies:** 2\
**Last updated:** [November 4, 2021, 3:07pm UTC](https://discourse.julialang.org/t/simple-type-problem/70958 "2021-11-04T15:07:08Z")

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I have an abstract type, abstract type AT end and two mutable structs that are subtypes of AT: mutable struct S1 \<: AT #something end mutable struct S2 \<: AT #something end I would like to define a function …

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## [Registering packages with a title 17 license](https://discourse.julialang.org/t/registering-packages-with-a-title-17-license/70946)

<div class="topic-metadata">

**Author:** [@NicholasWMRitchie](https://discourse.julialang.org/u/NicholasWMRitchie)\
**Replies:** 3\
**Last updated:** [November 4, 2021, 2:43pm UTC](https://discourse.julialang.org/t/registering-packages-with-a-title-17-license/70946 "2021-11-04T14:43:24Z")

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I really appreciate that Julia enforces a liberal Open Source license on packages. However, I’ve run into a problem. As a US Government employee, I’m required by Title 17 United States Code Section 105 to release my w…

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## [Tutorial on Coupling Jumps](https://discourse.julialang.org/t/tutorial-on-coupling-jumps/70957)

<div class="topic-metadata">

**Author:** [@tom-plaa](https://discourse.julialang.org/u/tom-plaa)\
**Replies:** 0\
**Last updated:** [November 4, 2021, 2:42pm UTC](https://discourse.julialang.org/t/tutorial-on-coupling-jumps/70957 "2021-11-04T14:42:36Z")

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Didn’t create an issue on the repo because this might be just my interpretation being wrong. I am trying to run code based on the tutorial at Jump Diffusion page. It mentions that this is supposed to be a Cox process (…

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## [New package PuiseuxPolynomials](https://discourse.julialang.org/t/new-package-puiseuxpolynomials/70948)

<div class="topic-metadata">

**Author:** [@Jean\_Michel](https://discourse.julialang.org/u/Jean_Michel)\
**Replies:** 0\
**Last updated:** [November 4, 2021, 12:54pm UTC](https://discourse.julialang.org/t/new-package-puiseuxpolynomials/70948 "2021-11-04T12:54:51Z")

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I want to announce two new packages which go together. Here is the second one PuiseuxPolynomials I wanted to call this package Mvps, since this is the name of the data structure it provides, but could not reg…

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## [Mathematical Modeling PhD](https://discourse.julialang.org/t/mathematical-modeling-phd/70953)

<div class="topic-metadata">

**Author:** [@quantiota](https://discourse.julialang.org/u/quantiota)\
**Replies:** 0\
**Last updated:** [November 4, 2021, 2:14pm UTC](https://discourse.julialang.org/t/mathematical-modeling-phd/70953 "2021-11-04T14:14:25Z")

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Job title : Mathematical Modeling PhD Contract type : Short Term, 1 Year, start date June 1, 2022 Company name : QUANTIOTA Country: France City : Meylan Job description Develop mathematical models to investigate, a…

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## [Weights in gaussian process](https://discourse.julialang.org/t/weights-in-gaussian-process/70646)

<div class="topic-metadata">

**Author:** [@jzr](https://discourse.julialang.org/u/jzr)\
**Replies:** 7\
**Last updated:** [November 4, 2021, 1:51pm UTC](https://discourse.julialang.org/t/weights-in-gaussian-process/70646 "2021-11-04T13:51:07Z")

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I have a model like @willtebbutt’s TemporalGPs example https://github.com/JuliaGaussianProcesses/TemporalGPs.jl#learning-kernel-parameters-with-optimjl-parameterhandlingjl-and-zygotejl In my dataset, different observati…

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## [Anyone looking for Job in Germany? We use Julia and CSharp in Fintec](https://discourse.julialang.org/t/anyone-looking-for-job-in-germany-we-use-julia-and-csharp-in-fintec/70855)

<div class="topic-metadata">

**Author:** [@Impressium](https://discourse.julialang.org/u/Impressium)\
**Replies:** 0\
**Last updated:** [November 3, 2021, 9:20am UTC](https://discourse.julialang.org/t/anyone-looking-for-job-in-germany-we-use-julia-and-csharp-in-fintec/70855 "2021-11-03T09:20:32Z")

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Hi all :slight\_smile: We have a couple open positions. So if anyone is interested please message me directly. Cheers

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