# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=345

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**Page:** 346

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## [Solving Fixed-MILP Problem](https://discourse.julialang.org/t/solving-fixed-milp-problem/51749)

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**Author:** [@Deepedit](https://discourse.julialang.org/u/Deepedit)\
**Replies:** 12\
**Last updated:** [August 18, 2021, 2:44am UTC](https://discourse.julialang.org/t/solving-fixed-milp-problem/51749 "2021-08-18T02:44:54Z")

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Hello to all. I’m trying to solve some generation schedule problem and we need access to the dual variables for pricing. The problem is MILP and, since the dual variables are no available, we used some suggestion to fix …

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## [Catalyst/DifferentialEquations: Gillespie simulation not working for large chemical reaction networks](https://discourse.julialang.org/t/catalyst-differentialequations-gillespie-simulation-not-working-for-large-chemical-reaction-networks/66521)

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**Author:** [@uagaug](https://discourse.julialang.org/u/uagaug)\
**Replies:** 2\
**Last updated:** [August 18, 2021, 2:10am UTC](https://discourse.julialang.org/t/catalyst-differentialequations-gillespie-simulation-not-working-for-large-chemical-reaction-networks/66521 "2021-08-18T02:10:00Z")

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I have a large chemical reaction network that involves protein synthesis, degradation, binding, and catalysis. I was able to construct the network using Catalyst, and deterministic ODE simulation in Julia returns the sam…

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## [Cannot set the starting point for LP](https://discourse.julialang.org/t/cannot-set-the-starting-point-for-lp/66531)

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**Author:** [@Aida\_Khajavirad](https://discourse.julialang.org/u/Aida_Khajavirad)\
**Replies:** 9\
**Last updated:** [August 17, 2021, 9:53pm UTC](https://discourse.julialang.org/t/cannot-set-the-starting-point-for-lp/66531 "2021-08-17T21:53:19Z")

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Hello, I m trying to solve an LP where my variable has the following form @variable(model, x\[i=1:N-1, j=i+1:N, k=1:d, l=1:d\] \>= 0) I ve been struggling to set a starting point, I tried set\_start\_value but i get error…

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## [Connection between sensitivity algorithm and gradient calculation of the loss function](https://discourse.julialang.org/t/connection-between-sensitivity-algorithm-and-gradient-calculation-of-the-loss-function/66550)

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**Author:** [@hardy](https://discourse.julialang.org/u/hardy)\
**Replies:** 6\
**Last updated:** [August 17, 2021, 9:22pm UTC](https://discourse.julialang.org/t/connection-between-sensitivity-algorithm-and-gradient-calculation-of-the-loss-function/66550 "2021-08-17T21:22:31Z")

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I’m new to Julia and ML and try to understand the basics. I have defined an ODE problem with 2 parameters. This is used for the prediction in my loss function. This loss function is now used in turn to optimize the para…

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## [MethodError: no method matching in JuMP](https://discourse.julialang.org/t/methoderror-no-method-matching-in-jump/66543)

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**Author:** [@zhangsanle](https://discourse.julialang.org/u/zhangsanle)\
**Replies:** 1\
**Last updated:** [August 17, 2021, 8:09pm UTC](https://discourse.julialang.org/t/methoderror-no-method-matching-in-jump/66543 "2021-08-17T20:09:34Z")

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I am new in julia. When i use JuMP, i meet some problems: MethodError: no method matching (::Interpolations.Extrapolation{Float64, 1, ScaledInterpolation{Float64, 1, Interpolations.BSplineInterpolation{Float64, 1, Vector…

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## [Pixel buffer objects](https://discourse.julialang.org/t/pixel-buffer-objects/66557)

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**Author:** [@Jakub\_Mitura](https://discourse.julialang.org/u/Jakub_Mitura)\
**Replies:** 0\
**Last updated:** [August 17, 2021, 3:33pm UTC](https://discourse.julialang.org/t/pixel-buffer-objects/66557 "2021-08-17T15:33:31Z")

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Hello I am trying to implement OpenGl pixel buffer object, becouse fast upload of data to texture is critical for my use case. My code that tries to implement it (using ModernGl.jl) juliaDataType= UInt8 toSend = ones…

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## [How to convert a JPEG image (from mobile) to a stantard 60k Array{ColorTypes.Gray{FixedPointNumbers.Normed{UInt8, 8}}, 2}) (from Flux.Data.MNIST)?](https://discourse.julialang.org/t/how-to-convert-a-jpeg-image-from-mobile-to-a-stantard-60k-array-colortypes-gray-fixedpointnumbers-normed-uint8-8-2-from-flux-data-mnist/66475)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 5\
**Last updated:** [August 17, 2021, 10:20am UTC](https://discourse.julialang.org/t/how-to-convert-a-jpeg-image-from-mobile-to-a-stantard-60k-array-colortypes-gray-fixedpointnumbers-normed-uint8-8-2-from-flux-data-mnist/66475 "2021-08-17T10:20:15Z")

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For an exercise I want to let students draw their own digits, scan them with a mobile and let a MINST-trained flux NN to category them. I see that the single MINST images are of type Matrix{ColorTypes.Gray{FixedPointNum…

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## [Question on QSIR Model and Flux.train for COVID-19 SIR data](https://discourse.julialang.org/t/question-on-qsir-model-and-flux-train-for-covid-19-sir-data/66422)

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**Author:** [@msteele-uofa-ece](https://discourse.julialang.org/u/msteele-uofa-ece)\
**Replies:** 3\
**Last updated:** [August 16, 2021, 9:33pm UTC](https://discourse.julialang.org/t/question-on-qsir-model-and-flux-train-for-covid-19-sir-data/66422 "2021-08-16T21:33:32Z")

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Hello, My name is Manuel Steele. I am a graduate student at St. Mary’s College for data science (Notre Dame, IN). I applied the model at the github site below to a smaller county in North Dakota. The model was succes…

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## [GLMakie: how to plot two images with transparency?](https://discourse.julialang.org/t/glmakie-how-to-plot-two-images-with-transparency/66492)

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**Author:** [@mariusd](https://discourse.julialang.org/u/mariusd)\
**Replies:** 3\
**Last updated:** [August 16, 2021, 8:47pm UTC](https://discourse.julialang.org/t/glmakie-how-to-plot-two-images-with-transparency/66492 "2021-08-16T20:47:15Z")

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I’m using GLMakie to display 2 images. GLMakie.image(GLMakie.rotr90(image\_data)) GLMakie.image!(GLMakie.rotr90(some\_extra\_data), colormap=“viridis”) This code will display “some\_extra\_data” and the “image\_data” is no …

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## [Flux question: best way to write a function that reuses some terms](https://discourse.julialang.org/t/flux-question-best-way-to-write-a-function-that-reuses-some-terms/66510)

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**Author:** [@IRM](https://discourse.julialang.org/u/IRM)\
**Replies:** 1\
**Last updated:** [August 16, 2021, 8:43pm UTC](https://discourse.julialang.org/t/flux-question-best-way-to-write-a-function-that-reuses-some-terms/66510 "2021-08-16T20:43:45Z")

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I have a question about the best (most computationally efficient) way to write functions for automatic differentiation in Flux in which some terms are reused. The particular example I give is motivated by the paper Jauc…

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## [Unstack using row numbers](https://discourse.julialang.org/t/unstack-using-row-numbers/66432)

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**Author:** [@feanor12](https://discourse.julialang.org/u/feanor12)\
**Replies:** 5\
**Last updated:** [August 16, 2021, 7:08pm UTC](https://discourse.julialang.org/t/unstack-using-row-numbers/66432 "2021-08-16T19:08:28Z")

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I have a table with multiple column pairs I dictating x and y values. If I stack them I can add columns bases on the column names for each pair, but do unstack them I need the original row numbers again. What is the bes…

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## [Significant allocations with Callbacks (Tsit5)](https://discourse.julialang.org/t/significant-allocations-with-callbacks-tsit5/66467)

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**Author:** [@Amarantine](https://discourse.julialang.org/u/Amarantine)\
**Replies:** 4\
**Last updated:** [August 16, 2021, 5:58pm UTC](https://discourse.julialang.org/t/significant-allocations-with-callbacks-tsit5/66467 "2021-08-16T17:58:40Z")

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I have a reasonably optimized ODE problem where I used callback for terminating the integrator when some values get too large. Without callback I have (43 allocations: 16.23 KiB), and with callback I have (42,065,928 all…

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## [Flux assumes only trainable parameters should be moved to GPU](https://discourse.julialang.org/t/flux-assumes-only-trainable-parameters-should-be-moved-to-gpu/66429)

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**Author:** [@SebastianCallh](https://discourse.julialang.org/u/SebastianCallh)\
**Replies:** 3\
**Last updated:** [August 16, 2021, 4:38pm UTC](https://discourse.julialang.org/t/flux-assumes-only-trainable-parameters-should-be-moved-to-gpu/66429 "2021-08-16T16:38:13Z")

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And that’s not always a good assumption! I am working on a masked dense layer, which looks something like this struct MaskedDense{F, M \<: AbstractMatrix, B \<: AbstractVector} W::M b::B M::AbstractMatrix{Bool} σ:…

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## [How to use \`bfs\_tree\` and \`dfs\_tree\` from \`LightGraphs.jl\`](https://discourse.julialang.org/t/how-to-use-bfs-tree-and-dfs-tree-from-lightgraphs-jl/66331)

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**Author:** [@mroavi](https://discourse.julialang.org/u/mroavi)\
**Replies:** 8\
**Last updated:** [August 16, 2021, 8:55am UTC](https://discourse.julialang.org/t/how-to-use-bfs-tree-and-dfs-tree-from-lightgraphs-jl/66331 "2021-08-16T08:55:19Z")

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I’m trying to understand how to use bfs\_tree and dfs\_tree from LightGraphs.jl . They both return the same graph so I don’t know how to extract the actual order in which the nodes were visited. using LightGraphs g = dou…

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## [Significant allocations with Callbacks with lazy interpolation (Vern methods)](https://discourse.julialang.org/t/significant-allocations-with-callbacks-with-lazy-interpolation-vern-methods/51080)

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**Author:** [@Lachlan-Bn](https://discourse.julialang.org/u/Lachlan-Bn)\
**Replies:** 9\
**Last updated:** [August 16, 2021, 8:00am UTC](https://discourse.julialang.org/t/significant-allocations-with-callbacks-with-lazy-interpolation-vern-methods/51080 "2021-08-16T08:00:12Z")

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I have a question that probably has a simple answer and is more conceptual, so I haven’t yet written a MWE. I have a small system with low error tolerance that, ignoring any callbacks, is reasonably efficient in terms o…

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## [ModelingToolkit - MethodError on isequal()](https://discourse.julialang.org/t/modelingtoolkit-methoderror-on-isequal/66440)

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**Author:** [@braamvandyk](https://discourse.julialang.org/u/braamvandyk)\
**Replies:** 2\
**Last updated:** [August 15, 2021, 5:33pm UTC](https://discourse.julialang.org/t/modelingtoolkit-methoderror-on-isequal/66440 "2021-08-15T17:33:11Z")

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My apologies if this is something really simple. I have looked at the docs and whatever examples I could find, but I am beginning to confuse the trees for the forest. Any directions would be greatly appreciated. I am tr…

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## [Horovod and Flux / Julia](https://discourse.julialang.org/t/horovod-and-flux-julia/53550)

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**Author:** [@Tomas\_Pevny](https://discourse.julialang.org/u/Tomas_Pevny)\
**Replies:** 7\
**Last updated:** [August 15, 2021, 4:46pm UTC](https://discourse.julialang.org/t/horovod-and-flux-julia/53550 "2021-08-15T16:46:14Z")

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Hi all, I wonder if anyone was trying to use horovod with Flux (or Julia in general). Thanks for a answer. Best wishes, Tomas

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## [Simple function to blur an image?](https://discourse.julialang.org/t/simple-function-to-blur-an-image/66417)

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**Author:** [@NHDaly](https://discourse.julialang.org/u/NHDaly)\
**Replies:** 4\
**Last updated:** [August 15, 2021, 9:53am UTC](https://discourse.julialang.org/t/simple-function-to-blur-an-image/66417 "2021-08-15T09:53:24Z")

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Hi all - today i found myself wanting to blur an image, and i figured it should be easy to find an example online. But I wasn’t able to find one… I’m sure that i’m just not searching for the right terms, because I am by…

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## [LDLt factorization for sparse matrix](https://discourse.julialang.org/t/ldlt-factorization-for-sparse-matrix/57011)

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**Author:** [@nbakas](https://discourse.julialang.org/u/nbakas)\
**Replies:** 2\
**Last updated:** [August 14, 2021, 7:50pm UTC](https://discourse.julialang.org/t/ldlt-factorization-for-sparse-matrix/57011 "2021-08-14T19:50:27Z")

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I am trying to compute the LDLt factorization for sparse matrix, which is symmetric and positive definite, and get the L and D factors. I tried many things, but I don’t yet have a solution. For example, julia\> C=ldlt(x…

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## [Technical question about DelayEmbeddings.jl](https://discourse.julialang.org/t/technical-question-about-delayembeddings-jl/66057)

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**Author:** [@iamsuddhasattwa](https://discourse.julialang.org/u/iamsuddhasattwa)\
**Replies:** 12\
**Last updated:** [August 14, 2021, 5:18pm UTC](https://discourse.julialang.org/t/technical-question-about-delayembeddings-jl/66057 "2021-08-14T17:18:15Z")

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Hi, I was trying to use the DelayEmbeddings.jl package, and I am trying to find a means to obtain the optimal delay embedding parameters (tsu, DeltaT) for a given timeseries. However the documentation https://juliadynam…

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## [Instructions for deploying Genie applications to virtual machine and container platform](https://discourse.julialang.org/t/instructions-for-deploying-genie-applications-to-virtual-machine-and-container-platform/66381)

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**Author:** [@jaantollander](https://discourse.julialang.org/u/jaantollander)\
**Replies:** 0\
**Last updated:** [August 14, 2021, 8:40am UTC](https://discourse.julialang.org/t/instructions-for-deploying-genie-applications-to-virtual-machine-and-container-platform/66381 "2021-08-14T08:40:37Z")

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Hello! During summer 2021, I have been working at CSC, testing their cloud computing resources from the user standpoint. First, I used the Genie framework to create a simple web application with a user interface and JSON…

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## [Multi-level varying slopes with two clusters, cross classification](https://discourse.julialang.org/t/multi-level-varying-slopes-with-two-clusters-cross-classification/62036)

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**Author:** [@Neal](https://discourse.julialang.org/u/Neal)\
**Replies:** 16\
**Last updated:** [August 14, 2021, 8:35am UTC](https://discourse.julialang.org/t/multi-level-varying-slopes-with-two-clusters-cross-classification/62036 "2021-08-14T08:35:26Z")

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Hello, I am working through StatisticalRethinking books with multi-level varying slopes with two clusters, cross classification model I run the stan model which finished sampling about two minutes. To build the mod…

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## [Editing titles after creating a Makie plot](https://discourse.julialang.org/t/editing-titles-after-creating-a-makie-plot/66352)

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**Author:** [@jlchan](https://discourse.julialang.org/u/jlchan)\
**Replies:** 6\
**Last updated:** [August 14, 2021, 12:05am UTC](https://discourse.julialang.org/t/editing-titles-after-creating-a-makie-plot/66352 "2021-08-14T00:05:48Z")

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I’m customizing Makie.plot to edit axis properties due to Accessing axis in Makie plot recipes. My function looks something like this: function foo(fig = Makie.Figure()) axes = \[Makie.Axis(fig\[i,j\]) for j in 1:3, i in…

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## [Row-wise mean of columns in a DataFrame](https://discourse.julialang.org/t/row-wise-mean-of-columns-in-a-dataframe/66358)

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**Author:** [@hdavid16](https://discourse.julialang.org/u/hdavid16)\
**Replies:** 4\
**Last updated:** [August 13, 2021, 11:58pm UTC](https://discourse.julialang.org/t/row-wise-mean-of-columns-in-a-dataframe/66358 "2021-08-13T23:58:49Z")

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I saw a post where @bkamins explained how to add a column that has the sum of the rows in selected columns ( (Julia) Assigning DataFrame column sum to a new column - Stack Overflow). Is there a way to use transform to do…

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## [ANN: DataFramesMeta 0.9.0 release](https://discourse.julialang.org/t/ann-dataframesmeta-0-9-0-release/66342)

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**Author:** [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)\
**Replies:** 1\
**Last updated:** [August 13, 2021, 5:41pm UTC](https://discourse.julialang.org/t/ann-dataframesmeta-0-9-0-release/66342 "2021-08-13T17:41:48Z")

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I am proud to announce the 0.9.0 release of DataFramesMeta.jl. We have three big changes inspired by DataFrameMacros.jl Better support for row-wise transformations: We now export @rtransform, @rselect, and @rsubset, a…

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## [GeoArrays band math](https://discourse.julialang.org/t/geoarrays-band-math/65947)

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**Author:** [@KrOstir](https://discourse.julialang.org/u/KrOstir)\
**Replies:** 7\
**Last updated:** [August 13, 2021, 3:15pm UTC](https://discourse.julialang.org/t/geoarrays-band-math/65947 "2021-08-13T15:15:20Z")

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I am working with an GeoArray and would like to perform band maths with it, i.e. compute NDVI from bands. I am currently doing the following: # Read Sentinel-2 data fn = download("https://bitbucket.org/earthobservation/…

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## [GPU-Kernel function for fast matrix multiplication using shared memory](https://discourse.julialang.org/t/gpu-kernel-function-for-fast-matrix-multiplication-using-shared-memory/66341)

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**Author:** [@DanielZ](https://discourse.julialang.org/u/DanielZ)\
**Replies:** 1\
**Last updated:** [August 13, 2021, 2:08pm UTC](https://discourse.julialang.org/t/gpu-kernel-function-for-fast-matrix-multiplication-using-shared-memory/66341 "2021-08-13T14:08:20Z")

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\[Copied from a Slack-Conversation:\] Me (Daniel): Hello, we try to implement a matrix multiplication in a kernel function using shared memory. However, our code in the kernel\_matmul\_fast function calculates a wrong resu…

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## [Row number in DataFrames groupby query](https://discourse.julialang.org/t/row-number-in-dataframes-groupby-query/57319)

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**Author:** [@bdeonovic](https://discourse.julialang.org/u/bdeonovic)\
**Replies:** 5\
**Last updated:** [August 13, 2021, 1:30pm UTC](https://discourse.julialang.org/t/row-number-in-dataframes-groupby-query/57319 "2021-08-13T13:30:10Z")

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I’m trying to understand how to do data manipulations in DataFrames (+ Query or + DataFramesMeta or +LINQ), in particular today I am looking to get rownumber in a groupby query For MWE consider df = DataFrame(a=repeat(…

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## [Combining multiple-shooting with out-of-ODE multithreading](https://discourse.julialang.org/t/combining-multiple-shooting-with-out-of-ode-multithreading/66338)

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**Author:** [@cmarcotte](https://discourse.julialang.org/u/cmarcotte)\
**Replies:** 1\
**Last updated:** [August 13, 2021, 12:05pm UTC](https://discourse.julialang.org/t/combining-multiple-shooting-with-out-of-ode-multithreading/66338 "2021-08-13T12:05:41Z")

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DiffEqFlux has examples for multiple shooting and out-of-ODE multithreading here and here, respectively. This seems like a natural pairing, but it seems like multiple\_shoot is written for a completely serial implementat…

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## [Gradient of expression with JuMP variables](https://discourse.julialang.org/t/gradient-of-expression-with-jump-variables/66259)

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**Author:** [@ver\_kh](https://discourse.julialang.org/u/ver_kh)\
**Replies:** 3\
**Last updated:** [August 13, 2021, 7:16am UTC](https://discourse.julialang.org/t/gradient-of-expression-with-jump-variables/66259 "2021-08-13T07:16:53Z")

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Hi! I have a complex nonlinear expression built with JuMP variables. And now I want to find gradient of this expression with respect to these variables. What package will be helpful in this situation?

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