# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=250

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**Page:** 251

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## [Univariate feature selection](https://discourse.julialang.org/t/univariate-feature-selection/87414)

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**Author:** [@lucasmsoares96](https://discourse.julialang.org/u/lucasmsoares96)\
**Replies:** 1\
**Last updated:** [September 18, 2022, 9:07pm UTC](https://discourse.julialang.org/t/univariate-feature-selection/87414 "2022-09-18T21:07:37Z")

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I’m having trouble finding a feature selection using Univariate feature selection in Julia. In scikit-learn this is possible as follows: from sklearn.datasets import load\_iris from sklearn.feature\_selection import Selec…

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## [How to count the number of categories present in a column of a DataFrame](https://discourse.julialang.org/t/how-to-count-the-number-of-categories-present-in-a-column-of-a-dataframe/33244)

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**Author:** [@philc](https://discourse.julialang.org/u/philc)\
**Replies:** 8\
**Last updated:** [September 18, 2022, 4:01pm UTC](https://discourse.julialang.org/t/how-to-count-the-number-of-categories-present-in-a-column-of-a-dataframe/33244 "2022-09-18T16:01:18Z")

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Hello, In a dataframe with columns :A, :B, :C where :B contains categorical data, I would like to count the number of categories present in the different subdataframes obtained through groupby(df,:A), and finally gettin…

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## [How to draw a directed graph of transition matrix](https://discourse.julialang.org/t/how-to-draw-a-directed-graph-of-transition-matrix/87399)

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**Author:** [@Christopher\_Fisher](https://discourse.julialang.org/u/Christopher_Fisher)\
**Replies:** 2\
**Last updated:** [September 18, 2022, 9:59am UTC](https://discourse.julialang.org/t/how-to-draw-a-directed-graph-of-transition-matrix/87399 "2022-09-18T09:59:41Z")

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Hi all, I would like to draw a network to visualize a transition matrix. I was wondering if there is a package somewhere that automatically generates a directed graph from a transition matrix. Here is an example of what…

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## [How to concisely define a recursive constraint？](https://discourse.julialang.org/t/how-to-concisely-define-a-recursive-constraint/87411)

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**Author:** [@WuSiren](https://discourse.julialang.org/u/WuSiren)\
**Replies:** 4\
**Last updated:** [September 18, 2022, 1:55am UTC](https://discourse.julialang.org/t/how-to-concisely-define-a-recursive-constraint/87411 "2022-09-18T01:55:31Z")

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How to concisely define a recursive constraint with JuMP, for example: x\_{t}-x\_{t-1}\\geqslant 1\\quad\\forall t = 1,\\cdots,T, where x\_0=0 but I don’t want to define an extra variable for it. In another words, I want to …

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## [Setting font of minus sign in exponent in Makie](https://discourse.julialang.org/t/setting-font-of-minus-sign-in-exponent-in-makie/87243)

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**Author:** [@yhchang96](https://discourse.julialang.org/u/yhchang96)\
**Replies:** 3\
**Last updated:** [September 18, 2022, 1:03am UTC](https://discourse.julialang.org/t/setting-font-of-minus-sign-in-exponent-in-makie/87243 "2022-09-18T01:03:11Z")

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With the following code: using CairoMakie CairoMakie.activate!() set\_theme!() set\_theme!(font = "Arial",) function log\_tick\_formatter(values) return map(v -\> "10" \* Makie.UnicodeFun.to\_superscript(round(Int64, v))…

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## [MathOptInterface.OTHER\_ERROR when trying to use ISRES of NLopt through JuMP](https://discourse.julialang.org/t/mathoptinterface-other-error-when-trying-to-use-isres-of-nlopt-through-jump/87420)

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**Author:** [@knkn1711](https://discourse.julialang.org/u/knkn1711)\
**Replies:** 1\
**Last updated:** [September 17, 2022, 11:41pm UTC](https://discourse.julialang.org/t/mathoptinterface-other-error-when-trying-to-use-isres-of-nlopt-through-jump/87420 "2022-09-17T23:41:49Z")

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I am trying to minimize a nonlinear function with nonlinear inequality constraints with NLopt and JuMP. In my test code below, I am minimizing a function with a known global minima. Local optimizers such as LD\_MMA fail…

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## [Difference between nprocs and nthreads](https://discourse.julialang.org/t/difference-between-nprocs-and-nthreads/87361)

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**Author:** [@HenriDeh](https://discourse.julialang.org/u/HenriDeh)\
**Replies:** 2\
**Last updated:** [September 17, 2022, 5:35pm UTC](https://discourse.julialang.org/t/difference-between-nprocs-and-nthreads/87361 "2022-09-17T17:35:58Z")

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Hello, I’m trying to get my head around distributed programming to execute a script on a cluster. My code works well on my workstation with one CPU. It internally uses @threads to parallelize some stuff within the main…

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## [Inset position and dimensions relative to the axes instead of relative to the plot](https://discourse.julialang.org/t/inset-position-and-dimensions-relative-to-the-axes-instead-of-relative-to-the-plot/87375)

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**Author:** [@Gregstrq](https://discourse.julialang.org/u/Gregstrq)\
**Replies:** 0\
**Last updated:** [September 16, 2022, 3:50pm UTC](https://discourse.julialang.org/t/inset-position-and-dimensions-relative-to-the-axes-instead-of-relative-to-the-plot/87375 "2022-09-16T15:50:57Z")

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I am trying to create an inset using Plots.jl. (To be specific, I am using GR backend). Is there a keyword argument, that will interpret bbox(x,y, w,h) in such a way that the length parameters are treated as the coordin…

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## [Using ModelingToolkit.jl to model a matrix ODE](https://discourse.julialang.org/t/using-modelingtoolkit-jl-to-model-a-matrix-ode/82490)

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**Author:** [@golanor](https://discourse.julialang.org/u/golanor)\
**Replies:** 3\
**Last updated:** [September 17, 2022, 12:44pm UTC](https://discourse.julialang.org/t/using-modelingtoolkit-jl-to-model-a-matrix-ode/82490 "2022-09-17T12:44:04Z")

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Hi, I’m trying to create a matrix ODE using ModelingToolkit,jl (to simplify autodiff and code optimization), but I’m receiving an error which I did not find in any of the issues of the library. Any idea what I’m doing w…

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## [Help to adapt the resolution of an ODE in Matlab to Julia](https://discourse.julialang.org/t/help-to-adapt-the-resolution-of-an-ode-in-matlab-to-julia/87389)

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**Author:** [@lucasmsoares96](https://discourse.julialang.org/u/lucasmsoares96)\
**Replies:** 3\
**Last updated:** [September 17, 2022, 6:41am UTC](https://discourse.julialang.org/t/help-to-adapt-the-resolution-of-an-ode-in-matlab-to-julia/87389 "2022-09-17T06:41:18Z")

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Hello guys. I’m having trouble adapting a Matlab code that resolves a second-order ODE to the Julia equivalent. This is the code in Matlab. It plots a graph with 3 curves: syms y(x); dy = diff(y); edo = diff(y,x,2) == …

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## [Equally sized grid cells in Makie](https://discourse.julialang.org/t/equally-sized-grid-cells-in-makie/87373)

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**Author:** [@psterzinger](https://discourse.julialang.org/u/psterzinger)\
**Replies:** 2\
**Last updated:** [September 16, 2022, 2:49pm UTC](https://discourse.julialang.org/t/equally-sized-grid-cells-in-makie/87373 "2022-09-16T14:49:25Z")

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Hi, I am trying to place 5 plots in a grid with 3 rows and 4 columns so that the first plot spans cols 2:3 in row 1 the remaining plots span cols 1:2, 3:4 in rows 2,3 all plots are of the same size However, it seems …

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## [Φ(−600) = 6.546588 205807 692852 105927 713888 108782 119412 831853 177211 16943e − 78177](https://discourse.julialang.org/t/600-6-546588-205807-692852-105927-713888-108782-119412-831853-177211-16943e-78177/87309)

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**Author:** [@blackeneth](https://discourse.julialang.org/u/blackeneth)\
**Replies:** 3\
**Last updated:** [September 16, 2022, 5:50am UTC](https://discourse.julialang.org/t/600-6-546588-205807-692852-105927-713888-108782-119412-831853-177211-16943e-78177/87309 "2022-09-16T05:50:19Z")

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The paper Approximations to the Normal Distribution Function and An Extended Table for the Mean Range of the Normal Variables by Kiani, M and Panaretos, J and Psarakis, S and Saleem, M (2008) reviews algorithms for compu…

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## [Multivariate nonlinear constrained optimization using JuMP and ForwardDiff (Automatic Differentiation)](https://discourse.julialang.org/t/multivariate-nonlinear-constrained-optimization-using-jump-and-forwarddiff-automatic-differentiation/87338)

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**Author:** [@dhathri](https://discourse.julialang.org/u/dhathri)\
**Replies:** 1\
**Last updated:** [September 15, 2022, 9:52pm UTC](https://discourse.julialang.org/t/multivariate-nonlinear-constrained-optimization-using-jump-and-forwarddiff-automatic-differentiation/87338 "2022-09-15T21:52:17Z")

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Hi, I am new to Julia and I am trying to understand how to use JuMP/ForwardDiff to transfer a collocation algorithm (nlp problem) written in MATLAB. I use fmincon in MATLAB with a nonlinear function that returns a vector…

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## [Nonuniform fast Hankel transform](https://discourse.julialang.org/t/nonuniform-fast-hankel-transform/87324)

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**Author:** [@jinml](https://discourse.julialang.org/u/jinml)\
**Replies:** 3\
**Last updated:** [September 15, 2022, 7:20pm UTC](https://discourse.julialang.org/t/nonuniform-fast-hankel-transform/87324 "2022-09-15T19:20:28Z")

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Hi, does anyone know about any packages that may be able to compute nonuniform fast Hankel transform of continuous functions? I saw this thread mentioning a few options for Fourier transform, which don’t seem to have wha…

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## [How to distribute arrays part of struct with MPI (MPI.jl)](https://discourse.julialang.org/t/how-to-distribute-arrays-part-of-struct-with-mpi-mpi-jl/87305)

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**Author:** [@verseve](https://discourse.julialang.org/u/verseve)\
**Replies:** 0\
**Last updated:** [September 15, 2022, 8:30am UTC](https://discourse.julialang.org/t/how-to-distribute-arrays-part-of-struct-with-mpi-mpi-jl/87305 "2022-09-15T08:30:32Z")

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I am wondering what the best approach is to distribute arrays that are part of a struct with MPI. Example of such a struct (partly): @get\_units @with\_kw struct SBM{T,N,M} Δt::T | "s" maxlayers::Int | "-" n:…

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## [Best practices for defining stochastic affect! functions for Jump Problems (RNG)](https://discourse.julialang.org/t/best-practices-for-defining-stochastic-affect-functions-for-jump-problems-rng/87202)

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**Author:** [@tom-plaa](https://discourse.julialang.org/u/tom-plaa)\
**Replies:** 7\
**Last updated:** [September 15, 2022, 12:43pm UTC](https://discourse.julialang.org/t/best-practices-for-defining-stochastic-affect-functions-for-jump-problems-rng/87202 "2022-09-15T12:43:42Z")

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I have created a small module based on DifferentialEquations to help me define a certain kind of stochastic differential equations where the stochastic processes are Lévy processes. As the jumps are stochastic, the kind …

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## [Help on terminology: multiprocessor vs. multicore](https://discourse.julialang.org/t/help-on-terminology-multiprocessor-vs-multicore/87066)

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**Author:** [@HJW019](https://discourse.julialang.org/u/HJW019)\
**Replies:** 12\
**Last updated:** [September 15, 2022, 4:25am UTC](https://discourse.julialang.org/t/help-on-terminology-multiprocessor-vs-multicore/87066 "2022-09-15T04:25:46Z")

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I am trying to understand the definitions of “multiprocessors” and “multicores” and it seems different sources have different definitions. I am mainly confused by whether the terms are defined by the numbers of physical …

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## [Converting UTM to EPSG:5389](https://discourse.julialang.org/t/converting-utm-to-epsg-5389/87280)

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**Author:** [@ameresv](https://discourse.julialang.org/u/ameresv)\
**Replies:** 5\
**Last updated:** [September 14, 2022, 10:20pm UTC](https://discourse.julialang.org/t/converting-utm-to-epsg-5389/87280 "2022-09-14T22:20:54Z")

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It could sound like a silly question, but I am having trouble converting points from UTM to long - lat (researching a bit, I found that I need is EPSG:5389 because is on the Southern side of Peru). So, the data looks li…

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## [More flexible Distributions package](https://discourse.julialang.org/t/more-flexible-distributions-package/87016)

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**Author:** [@pedro.rafae](https://discourse.julialang.org/u/pedro.rafae)\
**Replies:** 10\
**Last updated:** [September 14, 2022, 8:09pm UTC](https://discourse.julialang.org/t/more-flexible-distributions-package/87016 "2022-09-14T20:09:13Z")

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Dear friends, I am a statistician and I have all my training in this area. In my PhD I worked with probability distribution generators and recently I became interested in the Julia language. I come from the R language an…

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## [Conditionnal constraint](https://discourse.julialang.org/t/conditionnal-constraint/87157)

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**Author:** [@Zizilabg](https://discourse.julialang.org/u/Zizilabg)\
**Replies:** 6\
**Last updated:** [September 14, 2022, 5:48pm UTC](https://discourse.julialang.org/t/conditionnal-constraint/87157 "2022-09-14T17:48:04Z")

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Hello, I need help to implement a constraint. The goal is to assign students to courses. Some courses can have a maximum of 8 students, others can have a maximum of 12. I first wrote my constraint like this: For j in…

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## [Type conversion driving me crazy](https://discourse.julialang.org/t/type-conversion-driving-me-crazy/87253)

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**Author:** [@scotts](https://discourse.julialang.org/u/scotts)\
**Replies:** 10\
**Last updated:** [September 14, 2022, 10:38am UTC](https://discourse.julialang.org/t/type-conversion-driving-me-crazy/87253 "2022-09-14T10:38:53Z")

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I’ve wasted half a day in frustration just trying to clean up some simple data. Basically, it’s a bunch of numbers as strings that I’ve bought into a data frame and now just want to remove missing values, spaces, remove …

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## [Ticks with integer numbers only (instead of fractional values)](https://discourse.julialang.org/t/ticks-with-integer-numbers-only-instead-of-fractional-values/87267)

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**Author:** [@benoitseron](https://discourse.julialang.org/u/benoitseron)\
**Replies:** 2\
**Last updated:** [September 14, 2022, 11:40am UTC](https://discourse.julialang.org/t/ticks-with-integer-numbers-only-instead-of-fractional-values/87267 "2022-09-14T11:40:48Z")

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I am looking to make a scatter plot some values with x values that can only be integers (1,2,3…). By default, Julia will sometimes use x ticks that are integers values, or sometimes as floats, depending on the range of …

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## [Cannot evaluate a vector for some ProductDistribution](https://discourse.julialang.org/t/cannot-evaluate-a-vector-for-some-productdistribution/87224)

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**Author:** [@Luis\_Calderon](https://discourse.julialang.org/u/Luis_Calderon)\
**Replies:** 1\
**Last updated:** [September 14, 2022, 10:34am UTC](https://discourse.julialang.org/t/cannot-evaluate-a-vector-for-some-productdistribution/87224 "2022-09-14T10:34:38Z")

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Dear all, I wish to specify a scaled inverse Wishart as formulated in this pdf, bottom of page 3. I understand how to implement it and have the following code so far (focused on the distributions). I’m focused on the ca…

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## [Ticks detached when using colsize!(fig.layout, Relative(...)) in Makie](https://discourse.julialang.org/t/ticks-detached-when-using-colsize-fig-layout-relative-in-makie/87250)

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**Author:** [@yhchang96](https://discourse.julialang.org/u/yhchang96)\
**Replies:** 2\
**Last updated:** [September 14, 2022, 7:07am UTC](https://discourse.julialang.org/t/ticks-detached-when-using-colsize-fig-layout-relative-in-makie/87250 "2022-09-14T07:07:33Z")

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With the following code CairoMakie.activate!() set\_theme!() set\_theme!( Axis = ( xtickalign = 1, ytickalign = 1, xminortickalign = 1, yminortickalign = 1, xscale = log10, …

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## [How to omit arithmetic error of MIP solver in JuMP?](https://discourse.julialang.org/t/how-to-omit-arithmetic-error-of-mip-solver-in-jump/87242)

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**Author:** [@Jian\_ZUO](https://discourse.julialang.org/u/Jian_ZUO)\
**Replies:** 2\
**Last updated:** [September 13, 2022, 11:28pm UTC](https://discourse.julialang.org/t/how-to-omit-arithmetic-error-of-mip-solver-in-jump/87242 "2022-09-13T23:28:47Z")

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Hi all, I am working on a nonlinear type MIP optimization problem solved through JuMP. My solution is based on Juniper and HiGHS: using Juniper using HiGHS using JuMP using Ipopt R10, R20 = 0.18, 0.195 L11, L21 = 2.4…

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## [.csv number of rows](https://discourse.julialang.org/t/csv-number-of-rows/27475)

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**Author:** [@austinbean](https://discourse.julialang.org/u/austinbean)\
**Replies:** 6\
**Last updated:** [September 13, 2022, 9:41pm UTC](https://discourse.julialang.org/t/csv-number-of-rows/27475 "2022-09-13T21:41:16Z")

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Is there a clever way to determine the number of rows in large .csv or .tsv file without reading a whole column? I’m currently doing: CSV.File("big\_file.csv") |\> Tables.select(:first\_column\_name) |\> DataFrame which te…

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## [LIBSVM vs sklearn](https://discourse.julialang.org/t/libsvm-vs-sklearn/87235)

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**Author:** [@Maxim\_Lubov](https://discourse.julialang.org/u/Maxim_Lubov)\
**Replies:** 0\
**Last updated:** [September 13, 2022, 8:54pm UTC](https://discourse.julialang.org/t/libsvm-vs-sklearn/87235 "2022-09-13T20:54:38Z")

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I’m trying to port the SVC-based modelling from python/sklearn to Julia using the LIBSVM.jl package. However, I noticed one strange thing. Sklearn SVC outperforms LIBSVM.jl, although both are based on the same libsvm lib…

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## [Accessing T-Net in PointNet in Flux3D.jl](https://discourse.julialang.org/t/accessing-t-net-in-pointnet-in-flux3d-jl/87233)

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**Author:** [@wsshin](https://discourse.julialang.org/u/wsshin)\
**Replies:** 0\
**Last updated:** [September 13, 2022, 8:46pm UTC](https://discourse.julialang.org/t/accessing-t-net-in-pointnet-in-flux3d-jl/87233 "2022-09-13T20:46:08Z")

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I have a question about PointNet in Flux3D.jl. In the original PointNet paper, the author trained the “T-net” to make PointNet invariant w.r.t. rigid transformations of input point clouds (red dashed box below): Is …

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## [Creating a function to produce stratum indicators efficiently](https://discourse.julialang.org/t/creating-a-function-to-produce-stratum-indicators-efficiently/87229)

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**Author:** [@erickawaguchi](https://discourse.julialang.org/u/erickawaguchi)\
**Replies:** 4\
**Last updated:** [September 13, 2022, 7:42pm UTC](https://discourse.julialang.org/t/creating-a-function-to-produce-stratum-indicators-efficiently/87229 "2022-09-13T19:42:31Z")

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Hi all, I am trying to create a function that takes as inputs df, key, and S, where df: Data frame key: Variable to group on (namely subject ID) S: Number of strata and creates a column in df named stratum s…

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## [Plots.jl: removing a single axis](https://discourse.julialang.org/t/plots-jl-removing-a-single-axis/9897)

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**Author:** [@yha](https://discourse.julialang.org/u/yha)\
**Replies:** 9\
**Last updated:** [September 13, 2022, 6:31pm UTC](https://discourse.julialang.org/t/plots-jl-removing-a-single-axis/9897 "2022-09-13T18:31:36Z")

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I’m trying to remove the x axis (i.e., bottom border, x ticks and x labels) from a plot. For the sake of helping the documentation effort, here’s what I tried so far. My first guess was: plot(x,y,xaxis=nothing) but th…

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