# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=373

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**Page:** 374

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## [How to (properly) use the solution of a simulation in ModelingToolkit](https://discourse.julialang.org/t/how-to-properly-use-the-solution-of-a-simulation-in-modelingtoolkit/59686)

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**Author:** [@CodeLenz](https://discourse.julialang.org/u/CodeLenz)\
**Replies:** 4\
**Last updated:** [April 20, 2021, 8:16pm UTC](https://discourse.julialang.org/t/how-to-properly-use-the-solution-of-a-simulation-in-modelingtoolkit/59686 "2021-04-20T20:16:02Z")

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Hi there. I am starting to use the amazing ModellingToolkit, but I am afraid I am missing something important. So I apologize if my questions is silly. Suppose I have a model consisting of two differential equations, t…

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## [Bounding Correlation Coefficients for Multiple Problems with JuMP](https://discourse.julialang.org/t/bounding-correlation-coefficients-for-multiple-problems-with-jump/59690)

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**Author:** [@phantom](https://discourse.julialang.org/u/phantom)\
**Replies:** 1\
**Last updated:** [April 20, 2021, 7:57pm UTC](https://discourse.julialang.org/t/bounding-correlation-coefficients-for-multiple-problems-with-jump/59690 "2021-04-20T19:57:56Z")

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Hi this is a very elementary questions but I’m still trying to understand the code from this example for the correlation problem. The example I am using is the bounding correlation coefficients problem from “Convex Opti…

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## [Help: policy iteration](https://discourse.julialang.org/t/help-policy-iteration/59685)

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**Author:** [@ZettEff](https://discourse.julialang.org/u/ZettEff)\
**Replies:** 0\
**Last updated:** [April 20, 2021, 6:29pm UTC](https://discourse.julialang.org/t/help-policy-iteration/59685 "2021-04-20T18:29:36Z")

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I am struggling with the implementation of an (toy) optimization problem using dynamic programming. Although this is not a pure Julia question, I hope someone can help me with this. Being new to dynamic programming / re…

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## [Gtk: How do I resize a window programmatically?](https://discourse.julialang.org/t/gtk-how-do-i-resize-a-window-programmatically/59684)

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**Author:** [@johntrinder](https://discourse.julialang.org/u/johntrinder)\
**Replies:** 2\
**Last updated:** [April 20, 2021, 7:50pm UTC](https://discourse.julialang.org/t/gtk-how-do-i-resize-a-window-programmatically/59684 "2021-04-20T19:50:57Z")

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In Julia Gtk, how do I resize a window or widget/container programmatically?

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## [Quiver plot (Plots.pyplot) with different colors depending on the length of the arrow](https://discourse.julialang.org/t/quiver-plot-plots-pyplot-with-different-colors-depending-on-the-length-of-the-arrow/59577)

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**Author:** [@hardy](https://discourse.julialang.org/u/hardy)\
**Replies:** 11\
**Last updated:** [April 20, 2021, 7:01pm UTC](https://discourse.julialang.org/t/quiver-plot-plots-pyplot-with-different-colors-depending-on-the-length-of-the-arrow/59577 "2021-04-20T19:01:43Z")

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Hello, I am new to Julia and tried to plot the gradient field of a loss function. I can get the lengths of the arrows by norm(dx, dy). But I don’t know how to convert a vector of values (lengths) into a vector of colors…

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## [Generating "INSERT INTO" SQL statement](https://discourse.julialang.org/t/generating-insert-into-sql-statement/59106)

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**Author:** [@Laco\_Kovac](https://discourse.julialang.org/u/Laco_Kovac)\
**Replies:** 19\
**Last updated:** [April 20, 2021, 1:00pm UTC](https://discourse.julialang.org/t/generating-insert-into-sql-statement/59106 "2021-04-20T13:00:45Z")

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I have either LibPQ.Result or DataFrame as an input, and as output I need to generate SQL statement in the form: INSERT INTO table VALUES (v1,v2,v3), (v4,v5,v6); I cannot use LibPQ.load! because I don’t want to execute…

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## [String encoding with DelimitedFiles](https://discourse.julialang.org/t/string-encoding-with-delimitedfiles/59646)

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**Author:** [@amrods](https://discourse.julialang.org/u/amrods)\
**Replies:** 8\
**Last updated:** [April 20, 2021, 9:45am UTC](https://discourse.julialang.org/t/string-encoding-with-delimitedfiles/59646 "2021-04-20T09:45:50Z")

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I’m importing some files with DelimitedFiles and I keep getting some weird characters in the header. For example: julia\> using DelimitedFiles julia\> csv, names = readdlm("data1.csv", ',', header=true) julia\> names 1×5…

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## [GMM as collaborative filering: why it is better than k-nearest neighbours (KNN)?](https://discourse.julialang.org/t/gmm-as-collaborative-filering-why-it-is-better-than-k-nearest-neighbours-knn/59647)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 0\
**Last updated:** [April 20, 2021, 8:29am UTC](https://discourse.julialang.org/t/gmm-as-collaborative-filering-why-it-is-better-than-k-nearest-neighbours-knn/59647 "2021-04-20T08:29:23Z")

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I have this quotes from a MITx Machine Learning course (but these are from my notes, so I am no longer 100% sure they are exactly the lectures words): "There has been many improvements that has been added to this kind o…

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## [Plots GR axis break](https://discourse.julialang.org/t/plots-gr-axis-break/59322)

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**Author:** [@iHany](https://discourse.julialang.org/u/iHany)\
**Replies:** 5\
**Last updated:** [April 20, 2021, 12:48am UTC](https://discourse.julialang.org/t/plots-gr-axis-break/59322 "2021-04-20T00:48:53Z")

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Is it possible to plot a figure containing axis break like this using Plots.jl and GR backend? Especially in boxplot.

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## [How to detect container resize event in GTK Julia?](https://discourse.julialang.org/t/how-to-detect-container-resize-event-in-gtk-julia/59622)

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**Author:** [@johntrinder](https://discourse.julialang.org/u/johntrinder)\
**Replies:** 1\
**Last updated:** [April 19, 2021, 11:59pm UTC](https://discourse.julialang.org/t/how-to-detect-container-resize-event-in-gtk-julia/59622 "2021-04-19T23:59:27Z")

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I’ve searched and scoured google for an answer but to no avail :frowning:

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## [Getindex A\[i,j\] wrong complexity on SparseMatrixCSC?](https://discourse.julialang.org/t/getindex-a-i-j-wrong-complexity-on-sparsematrixcsc/59277)

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**Author:** [@bonevbs](https://discourse.julialang.org/u/bonevbs)\
**Replies:** 18\
**Last updated:** [April 19, 2021, 11:30pm UTC](https://discourse.julialang.org/t/getindex-a-i-j-wrong-complexity-on-sparsematrixcsc/59277 "2021-04-19T23:30:12Z")

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The complexity of extracting a sparse submatrix A\[i,j\] of size k x l from a large sparse matrix of size n with nnz entries should be O(k log k + l nz log k). Accessing my sparse matrices seemed very slow and I checked …

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## [ERROR: Unable to locate KNITRO installation, please check your environment variable KNITRODIR](https://discourse.julialang.org/t/error-unable-to-locate-knitro-installation-please-check-your-environment-variable-knitrodir/59619)

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**Author:** [@yecyn](https://discourse.julialang.org/u/yecyn)\
**Replies:** 1\
**Last updated:** [April 19, 2021, 11:12pm UTC](https://discourse.julialang.org/t/error-unable-to-locate-knitro-installation-please-check-your-environment-variable-knitrodir/59619 "2021-04-19T23:12:04Z")

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Hello, I’ve downloaded KNITRO from Artelys, and I have unpacked the zip file and have a folder named “knitro-12.3.0-MacOS-64” under my home file. However, while I was running the using KNITRO in jupyter notebook, I got…

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## [Lambda or Cloud Functions -- eventually possible?](https://discourse.julialang.org/t/lambda-or-cloud-functions-eventually-possible/39128)

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**Author:** [@tbeason](https://discourse.julialang.org/u/tbeason)\
**Replies:** 8\
**Last updated:** [April 19, 2021, 10:03pm UTC](https://discourse.julialang.org/t/lambda-or-cloud-functions-eventually-possible/39128 "2021-04-19T22:03:12Z")

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Things like AWS Lambda and/or Google Cloud Functions are basically just replacements for traditionally lightweight tasks that smart people realized could be done without a server. Right now, you can create these serverle…

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## [Bounding Correlation Coefficients with JuMP](https://discourse.julialang.org/t/bounding-correlation-coefficients-with-jump/59589)

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**Author:** [@phantom](https://discourse.julialang.org/u/phantom)\
**Replies:** 2\
**Last updated:** [April 19, 2021, 7:52pm UTC](https://discourse.julialang.org/t/bounding-correlation-coefficients-with-jump/59589 "2021-04-19T19:52:54Z")

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New to julia and this discussion group so I’m sorry if this is not a typical discussion topic or if I am breaching any norms here. I will do my best to pick up on things as I go. In “Convex Optimization” by Boyd there i…

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## [CUDA.randn! allocation](https://discourse.julialang.org/t/cuda-randn-allocation/59506)

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**Author:** [@zhiwei](https://discourse.julialang.org/u/zhiwei)\
**Replies:** 2\
**Last updated:** [April 19, 2021, 5:25pm UTC](https://discourse.julialang.org/t/cuda-randn-allocation/59506 "2021-04-19T17:25:22Z")

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Hello, I’m using CUDA.randn! on a CuArray and CUDA.@allocated reports memory allocations. This doesn’t happen for CUDA.rand!. I wonder if this is normal? julia\> rng = CURAND.default\_rng() julia\> a = CuArray{Float64}(u…

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## [Embed a Dash app in Genie.jl website](https://discourse.julialang.org/t/embed-a-dash-app-in-genie-jl-website/56616)

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**Author:** [@MLackner](https://discourse.julialang.org/u/MLackner)\
**Replies:** 1\
**Last updated:** [April 19, 2021, 5:05pm UTC](https://discourse.julialang.org/t/embed-a-dash-app-in-genie-jl-website/56616 "2021-04-19T17:05:58Z")

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Hi! I’m trying to embed a Dash.jl app in a website that is generated by Genie.jl. My approach is working with Stipple.jl apps but unfortunately, due to the lack of documentation I’m not able to do something useful with…

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## [Setup topology with ClusterManagers](https://discourse.julialang.org/t/setup-topology-with-clustermanagers/59591)

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**Author:** [@Gregstrq](https://discourse.julialang.org/u/Gregstrq)\
**Replies:** 8\
**Last updated:** [April 19, 2021, 3:12pm UTC](https://discourse.julialang.org/t/setup-topology-with-clustermanagers/59591 "2021-04-19T15:12:48Z")

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How does one pass topology to a cluster manager? Julia docs mention the setup of topology in the case when addprocs dispatches on machines, but not on a cluster manager. I am trying to do the following thing. I would …

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## [Complexity function center LightGraphs](https://discourse.julialang.org/t/complexity-function-center-lightgraphs/59592)

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**Author:** [@afazevedo](https://discourse.julialang.org/u/afazevedo)\
**Replies:** 0\
**Last updated:** [April 19, 2021, 1:29pm UTC](https://discourse.julialang.org/t/complexity-function-center-lightgraphs/59592 "2021-04-19T13:29:34Z")

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Hey guys, Someone know the complexity of the “center” function in the LightGraphs package? Futhermore, I take the opportunity to ask if there is any package that calculates complexity of functions in Julia. Thank you …

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## [Solving for the steady-state of a large nonlinear ODE in SciML](https://discourse.julialang.org/t/solving-for-the-steady-state-of-a-large-nonlinear-ode-in-sciml/50613)

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**Author:** [@briochemc](https://discourse.julialang.org/u/briochemc)\
**Replies:** 32\
**Last updated:** [April 19, 2021, 10:01am UTC](https://discourse.julialang.org/t/solving-for-the-steady-state-of-a-large-nonlinear-ode-in-sciml/50613 "2021-04-19T10:01:05Z")

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I have a few questions: What is the difference in scope between NonlinearSolve.jl and NLSolvers.jl/NLsolve.jl? What are the pros/cons of NonlinearSolve.jl vs NLSolvers.jl/NLsolve.jl? Are there any plans to include the …

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## [SCIP solver](https://discourse.julialang.org/t/scip-solver/59497)

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**Author:** [@mjanun](https://discourse.julialang.org/u/mjanun)\
**Replies:** 4\
**Last updated:** [April 19, 2021, 7:30am UTC](https://discourse.julialang.org/t/scip-solver/59497 "2021-04-19T07:30:30Z")

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How do we set number of threads for integer problems (MINLP or MILP) in SCIP? This code returns an error and I am not 100% sure that parallel\_maxnthreads is the right parameter to use. optimizer = SCIP.Optimizer(parall…

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## [Modifying solver parameters in JuMP after building the model](https://discourse.julialang.org/t/modifying-solver-parameters-in-jump-after-building-the-model/59509)

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**Author:** [@varun7rs](https://discourse.julialang.org/u/varun7rs)\
**Replies:** 3\
**Last updated:** [April 18, 2021, 8:44pm UTC](https://discourse.julialang.org/t/modifying-solver-parameters-in-jump-after-building-the-model/59509 "2021-04-18T20:44:30Z")

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I was working on a heuristic where I modify an ILP within a loop and solve it for a certain iterations. As of now, within the loop, I build the model repeatedly during each iteration which is costing me more time. Is the…

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## [Using DefaultDict as a (high dimension) SparseArray?](https://discourse.julialang.org/t/using-defaultdict-as-a-high-dimension-sparsearray/59554)

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**Author:** [@rpmuller](https://discourse.julialang.org/u/rpmuller)\
**Replies:** 0\
**Last updated:** [April 18, 2021, 4:56pm UTC](https://discourse.julialang.org/t/using-defaultdict-as-a-high-dimension-sparsearray/59554 "2021-04-18T16:56:20Z")

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I’m currently using dictionaries with multiple indices to store data from high dimension (12, in my case) sparse arrays. As far as I know, the structures in SparseArrays only handle arrays of dimension 1 and 2. Is ther…

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## [Inverse prediction](https://discourse.julialang.org/t/inverse-prediction/59535)

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**Author:** [@riot](https://discourse.julialang.org/u/riot)\
**Replies:** 0\
**Last updated:** [April 18, 2021, 12:19pm UTC](https://discourse.julialang.org/t/inverse-prediction/59535 "2021-04-18T12:19:36Z")

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I am looking for a way to do what I used to do with the DRC-package in R. Especially the prediction of x given y (inverse prediction e.g. in probit dose-response models). In R I used the functin ED() for this. Is there a…

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## [Getting problem data from jump model (semidefinite programming, etc.)](https://discourse.julialang.org/t/getting-problem-data-from-jump-model-semidefinite-programming-etc/59327)

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**Author:** [@Thomas](https://discourse.julialang.org/u/Thomas)\
**Replies:** 2\
**Last updated:** [April 18, 2021, 7:42am UTC](https://discourse.julialang.org/t/getting-problem-data-from-jump-model-semidefinite-programming-etc/59327 "2021-04-18T07:42:53Z")

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Hi everyone, after a quick search here and the API, I have not seen this question addressed to my liking so let me raise it: How to get the problem data in canonical form min dot(C,x) subject to Ax=b, that is from a mo…

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## [Priors for generated quantities in Turing?](https://discourse.julialang.org/t/priors-for-generated-quantities-in-turing/57572)

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**Author:** [@opera\_malenky](https://discourse.julialang.org/u/opera_malenky)\
**Replies:** 7\
**Last updated:** [April 18, 2021, 6:18am UTC](https://discourse.julialang.org/t/priors-for-generated-quantities-in-turing/57572 "2021-04-18T06:18:11Z")

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I have a Turing model where I need (in part) to do something like this: @model test() = begin x = ones(10) sigma ~ InverseGamma(1, 1) x ~ Normal(0, sigma) end m1 = sample(test(), NUTS(0.65), 1000) I was a …

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## [Same ODEProblem has differente results when variable is Float64 and Vector{Float64}](https://discourse.julialang.org/t/same-odeproblem-has-differente-results-when-variable-is-float64-and-vector-float64/59477)

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**Author:** [@Rafael\_FC](https://discourse.julialang.org/u/Rafael_FC)\
**Replies:** 2\
**Last updated:** [April 17, 2021, 8:08pm UTC](https://discourse.julialang.org/t/same-odeproblem-has-differente-results-when-variable-is-float64-and-vector-float64/59477 "2021-04-17T20:08:12Z")

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Hello! I’m having trouble with the following code. As of now it’s working fine, but if I change y0 (Float64) to y0\[1\] (Vector{Float64}) and dy to dy\[1\], it returns a wrong result. Since it’s a simple problem I must be …

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## [Batch time-series input for RNN](https://discourse.julialang.org/t/batch-time-series-input-for-rnn/59469)

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**Author:** [@Sunny](https://discourse.julialang.org/u/Sunny)\
**Replies:** 1\
**Last updated:** [April 17, 2021, 8:07pm UTC](https://discourse.julialang.org/t/batch-time-series-input-for-rnn/59469 "2021-04-17T20:07:49Z")

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How to form and feed a proper batch to feed to RNN? It is possible to apply RNN to batch of one data point time-series inputs: # single sample rnn = RNN(2,3) seq = ones(Float32,(2,10)) rnn(seq) # apply to 10 sample in…

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## [Delete all rows which have null values/missing values in 'all' the columns](https://discourse.julialang.org/t/delete-all-rows-which-have-null-values-missing-values-in-all-the-columns/59489)

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**Author:** [@harneet411](https://discourse.julialang.org/u/harneet411)\
**Replies:** 1\
**Last updated:** [April 17, 2021, 6:02pm UTC](https://discourse.julialang.org/t/delete-all-rows-which-have-null-values-missing-values-in-all-the-columns/59489 "2021-04-17T18:02:28Z")

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I am trying to find a similar functionality like in Python where in I can delete the rows which have ‘all’ null values in a row - code in python - Using Pandas dataframe ‘closed\_prices’ closed\_prices.dropna(axis=0, how…

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## [Julia package for dithering images?](https://discourse.julialang.org/t/julia-package-for-dithering-images/56844)

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**Author:** [@Phil\_Tomson](https://discourse.julialang.org/u/Phil_Tomson)\
**Replies:** 3\
**Last updated:** [April 17, 2021, 4:58pm UTC](https://discourse.julialang.org/t/julia-package-for-dithering-images/56844 "2021-04-17T16:58:41Z")

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Are there any Julia packages for dithering images? Specifically Floyd-Steinberg dithering? I noticed this one: GitHub - xianrenb/DitherImage.jl: Simple Julia Package for Image Dithering But it hasn’t been updated in 5 …

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## [Gradient not updating in call to optimize (Optim.jl)](https://discourse.julialang.org/t/gradient-not-updating-in-call-to-optimize-optim-jl/59448)

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**Author:** [@marcus-waldman](https://discourse.julialang.org/u/marcus-waldman)\
**Replies:** 2\
**Last updated:** [April 17, 2021, 4:03pm UTC](https://discourse.julialang.org/t/gradient-not-updating-in-call-to-optimize-optim-jl/59448 "2021-04-17T16:03:57Z")

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I’m trying to use the optimize function as part of the Optim.jl package with gradients that I provide. The problem I am having is that the function isn’t actually iterating–it simply computes the objective function once …

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