# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=410

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**Page:** 411

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## [PyTorch DataLoader equivalent for training large models with Flux](https://discourse.julialang.org/t/pytorch-dataloader-equivalent-for-training-large-models-with-flux/30763)

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**Author:** [@holylorenzo](https://discourse.julialang.org/u/holylorenzo)\
**Replies:** 16\
**Last updated:** [November 8, 2020, 8:58am UTC](https://discourse.julialang.org/t/pytorch-dataloader-equivalent-for-training-large-models-with-flux/30763 "2020-11-08T08:58:03Z")

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I’m trying to train a large computer vision model I built in Flux. Unfortunately the dataset does not fit into memory. Does something similar to PyTorch’s DataLoader exist as a Julia package? Is there an ongoing effort …

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## [Parsing arrays directly from text file](https://discourse.julialang.org/t/parsing-arrays-directly-from-text-file/49766)

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**Author:** [@h2ster](https://discourse.julialang.org/u/h2ster)\
**Replies:** 2\
**Last updated:** [November 8, 2020, 3:19am UTC](https://discourse.julialang.org/t/parsing-arrays-directly-from-text-file/49766 "2020-11-08T03:19:13Z")

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I’m currently working on a project where one of the functions generates a large amount of data and returns it as an vector, where each element of the vector is itself a vector with various levels of nesting. I use this d…

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## [Declare two exceptions in an equation](https://discourse.julialang.org/t/declare-two-exceptions-in-an-equation/49755)

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**Author:** [@carlos](https://discourse.julialang.org/u/carlos)\
**Replies:** 4\
**Last updated:** [November 7, 2020, 10:54pm UTC](https://discourse.julialang.org/t/declare-two-exceptions-in-an-equation/49755 "2020-11-07T22:54:40Z")

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Hi, I’m trying to declare two exceptions in the following equation but it doesn’t work like this: e52\[i=1:29,k=1:29;i != L,k != L\], -lambdaVI\[i\] \<= M\*BCC\[i,k\]

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## [How to fit a Dirichlet Distribution using MLE in Distributions.jl?](https://discourse.julialang.org/t/how-to-fit-a-dirichlet-distribution-using-mle-in-distributions-jl/49645)

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**Author:** [@stochastic\_guy](https://discourse.julialang.org/u/stochastic_guy)\
**Replies:** 6\
**Last updated:** [November 7, 2020, 9:53pm UTC](https://discourse.julialang.org/t/how-to-fit-a-dirichlet-distribution-using-mle-in-distributions-jl/49645 "2020-11-07T21:53:35Z")

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I would like to fit Dirichlet Distribution to all\_patterns using MLE in the Distributions package where alpha to Dirichlet is fill(1,k) and all\_patterns is a combination array all\_patterns = (p=(a,c)-\>c\<2 ? a : \[…

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## [Writing only a header with CSV.jl](https://discourse.julialang.org/t/writing-only-a-header-with-csv-jl/49746)

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**Author:** [@andferrari](https://discourse.julialang.org/u/andferrari)\
**Replies:** 2\
**Last updated:** [November 7, 2020, 6:26pm UTC](https://discourse.julialang.org/t/writing-only-a-header-with-csv-jl/49746 "2020-11-07T18:26:44Z")

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I am writing a csv file appending arrays with CSV.write(...;append=true). How can I write the header before I start to iterate? I have tried to create an empty table without success.

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## [Julia Equivalent of R's Flexdashboards - Project Idea](https://discourse.julialang.org/t/julia-equivalent-of-rs-flexdashboards-project-idea/33652)

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**Author:** [@phillc](https://discourse.julialang.org/u/phillc)\
**Replies:** 6\
**Last updated:** [November 7, 2020, 5:49pm UTC](https://discourse.julialang.org/t/julia-equivalent-of-rs-flexdashboards-project-idea/33652 "2020-11-07T17:49:55Z")

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I’d really like to use a product with Julia which is somewhat equivalent to R’s Flexdashboards. I’m aware of the excellent Dashboards.jl project, using Plotly’s Dash as the engine, which may ultimately suit my needs, bu…

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## [JuMP @constraint - "begin end" block not working](https://discourse.julialang.org/t/jump-constraint-begin-end-block-not-working/49734)

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**Author:** [@shashankchahar](https://discourse.julialang.org/u/shashankchahar)\
**Replies:** 2\
**Last updated:** [November 7, 2020, 5:14pm UTC](https://discourse.julialang.org/t/jump-constraint-begin-end-block-not-working/49734 "2020-11-07T17:14:54Z")

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Hi, I am trying to set some constraints in JuMP within Pluto. If I specify each constraint on a separate line then I don’t get an error message but if I try to put all the constraints in a begin-end block then Pluto giv…

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## [Display array as image in Pluto](https://discourse.julialang.org/t/display-array-as-image-in-pluto/48732)

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**Author:** [@dahnielson](https://discourse.julialang.org/u/dahnielson)\
**Replies:** 8\
**Last updated:** [November 7, 2020, 4:33pm UTC](https://discourse.julialang.org/t/display-array-as-image-in-pluto/48732 "2020-11-07T16:33:20Z")

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I’m pretty new to Julia and Pluto so this is my first stumbling block. How do I display an array as an image in Pluto? Say I have an 8x8 array of Float64 that I want to display as a gray scale image. The JuliaImages doc…

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## [Calling C vs Embedding Julia (C code)](https://discourse.julialang.org/t/calling-c-vs-embedding-julia-c-code/49599)

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**Author:** [@eduardovrs](https://discourse.julialang.org/u/eduardovrs)\
**Replies:** 4\
**Last updated:** [November 7, 2020, 1:24pm UTC](https://discourse.julialang.org/t/calling-c-vs-embedding-julia-c-code/49599 "2020-11-07T13:24:22Z")

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Calling C vs Embedding Julia in C code Hello World, I am new to Julia, and at the moment I am doing some research about the possibilities of combining an existing C code with new Julia functions. At the moment I have …

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## [Julia libdl\_find\_library in cluster](https://discourse.julialang.org/t/julia-libdl-find-library-in-cluster/49700)

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**Author:** [@j\_tanu](https://discourse.julialang.org/u/j_tanu)\
**Replies:** 15\
**Last updated:** [November 7, 2020, 11:48am UTC](https://discourse.julialang.org/t/julia-libdl-find-library-in-cluster/49700 "2020-11-07T11:48:11Z")

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Hi I am trying to run the Julia in my university cluster In the cluster, Julia is not installed as a module so I am running the .jl file by giving the exact location of the Julia executable. As of now, My code was singl…

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## [Gradient of gradient](https://discourse.julialang.org/t/gradient-of-gradient/49660)

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**Author:** [@jlmaccal](https://discourse.julialang.org/u/jlmaccal)\
**Replies:** 9\
**Last updated:** [November 6, 2020, 9:44pm UTC](https://discourse.julialang.org/t/gradient-of-gradient/49660 "2020-11-06T21:44:06Z")

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I’m implementing a model that requires using the gradients of a feedforward network with respect to its inputs as part of the loss function. I then need to train the network by differentiating the loss with respect to th…

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## [Component-based modelling in ModelingToolkit.jl with nonsingular mass matrix](https://discourse.julialang.org/t/component-based-modelling-in-modelingtoolkit-jl-with-nonsingular-mass-matrix/49140)

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**Author:** [@Dhruva2](https://discourse.julialang.org/u/Dhruva2)\
**Replies:** 13\
**Last updated:** [November 6, 2020, 8:51pm UTC](https://discourse.julialang.org/t/component-based-modelling-in-modelingtoolkit-jl-with-nonsingular-mass-matrix/49140 "2020-11-06T20:51:04Z")

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Hi, I essentially want to solve an easier version of the copy-paste example provided in the docs here. Instead of connecting the two lorenz systems via an algebraic equality, I want to add the state of one system as a ti…

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## [External Sorting Algorithms in julia?](https://discourse.julialang.org/t/external-sorting-algorithms-in-julia/49703)

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**Author:** [@Luapulu](https://discourse.julialang.org/u/Luapulu)\
**Replies:** 0\
**Last updated:** [November 6, 2020, 8:11pm UTC](https://discourse.julialang.org/t/external-sorting-algorithms-in-julia/49703 "2020-11-06T20:11:52Z")

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Does somebody have an implementation for external sorting algorithms in julia? If not, who would be interested? I’d like to have this available for HDF5Arrays.jl (WIP), which I’m working on.

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## [Some question about the structure of Turing models](https://discourse.julialang.org/t/some-question-about-the-structure-of-turing-models/48211)

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**Author:** [@mcql](https://discourse.julialang.org/u/mcql)\
**Replies:** 25\
**Last updated:** [November 6, 2020, 6:07pm UTC](https://discourse.julialang.org/t/some-question-about-the-structure-of-turing-models/48211 "2020-11-06T18:07:42Z")

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Hello, given a Turing model @model function λ(y) λ₁ ~ Exponential(alpha) for i in 1:length(y) y\[i\] ~ Poisson(λ₁) end end what is the meaning of the y array? I think it is used to compute the post…

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## [Calculate gradient of UDE model (without DiffEqFlux.sciml\_train)](https://discourse.julialang.org/t/calculate-gradient-of-ude-model-without-diffeqflux-sciml-train/49488)

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**Author:** [@bad\_at\_math](https://discourse.julialang.org/u/bad_at_math)\
**Replies:** 3\
**Last updated:** [November 6, 2020, 5:12pm UTC](https://discourse.julialang.org/t/calculate-gradient-of-ude-model-without-diffeqflux-sciml-train/49488 "2020-11-06T17:12:01Z")

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Hello everyone, I’m interested in using the SciML ecosystem to train universal differential equations models in Julia. However, I don’t want to have to rely on the sciml\_train function – I’m interested in explicitly work…

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## [Error/segfault in basic test of CUDA-aware MPI](https://discourse.julialang.org/t/error-segfault-in-basic-test-of-cuda-aware-mpi/31755)

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**Author:** [@samo](https://discourse.julialang.org/u/samo)\
**Replies:** 10\
**Last updated:** [November 6, 2020, 3:35pm UTC](https://discourse.julialang.org/t/error-segfault-in-basic-test-of-cuda-aware-mpi/31755 "2020-11-06T15:35:59Z")

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Problem A basic test of CUDA-aware MPI with MPI.jl fails on both our Cray supercomputer and on another cluster: 1) On Cray system 1.1) Test and error: omlins@dom101:~\> export MPICH\_RDMA\_ENABLED\_CUDA=1 omlins@nid00002:…

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## [Fastest JSON parser to julia](https://discourse.julialang.org/t/fastest-json-parser-to-julia/49639)

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**Author:** [@Marcell\_Havlik](https://discourse.julialang.org/u/Marcell_Havlik)\
**Replies:** 15\
**Last updated:** [November 6, 2020, 2:12pm UTC](https://discourse.julialang.org/t/fastest-json-parser-to-julia/49639 "2020-11-06T14:12:45Z")

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Hey Julianners, I just realised a speed comparison here: https://www.reddit.com/r/programming/comments/3pojrz/the\_fastest\_json\_parser\_in\_the\_world/ https://github.com/kostya/benchmarks#json where smidjson is one of th…

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## [Proper Julia syntax for Kriging interpolation with Geostats.jl?](https://discourse.julialang.org/t/proper-julia-syntax-for-kriging-interpolation-with-geostats-jl/49506)

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**Author:** [@CosmoProf](https://discourse.julialang.org/u/CosmoProf)\
**Replies:** 8\
**Last updated:** [November 6, 2020, 2:13am UTC](https://discourse.julialang.org/t/proper-julia-syntax-for-kriging-interpolation-with-geostats-jl/49506 "2020-11-06T02:13:42Z")

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Hi, I’m trying to use Kriging to interpolate between data values in a discrete array. The following code (and variations of it) give errors like, MethodError: no method matching EstimationProblem(::Set{Float64}, ::Regul…

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## [MLJFlux much faster for simple MNIST example than TensorFlow?](https://discourse.julialang.org/t/mljflux-much-faster-for-simple-mnist-example-than-tensorflow/49646)

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**Author:** [@simeonschaub](https://discourse.julialang.org/u/simeonschaub)\
**Replies:** 0\
**Last updated:** [November 5, 2020, 9:57pm UTC](https://discourse.julialang.org/t/mljflux-much-faster-for-simple-mnist-example-than-tensorflow/49646 "2020-11-05T21:57:26Z")

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I am trying to port this TensorFlow MNIST example to MLJFlux.jl. This is what I have so far, it is currently achieving an accuracy of 97.1%, which is pretty similar to the TensorFlow example: using MLJ, MLJFlux, Flux m…

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## [Optimizing over real matrices with eigenvalues in $(0,1)$](https://discourse.julialang.org/t/optimizing-over-real-matrices-with-eigenvalues-in-0-1/49630)

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**Author:** [@marcus](https://discourse.julialang.org/u/marcus)\
**Replies:** 3\
**Last updated:** [November 5, 2020, 5:35pm UTC](https://discourse.julialang.org/t/optimizing-over-real-matrices-with-eigenvalues-in-0-1/49630 "2020-11-05T17:35:58Z")

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I’m trying to optimize a function with respect to a real matrix M with all eigenvalues real and lying in the open interval (0,1). I know that for a real symmetric positive-definite matrix S, we can use the Cholesky fact…

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## [Solving a linear system of equalities and inequalities](https://discourse.julialang.org/t/solving-a-linear-system-of-equalities-and-inequalities/49579)

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**Author:** [@Huy\_Nguyen](https://discourse.julialang.org/u/Huy_Nguyen)\
**Replies:** 18\
**Last updated:** [November 5, 2020, 12:01pm UTC](https://discourse.julialang.org/t/solving-a-linear-system-of-equalities-and-inequalities/49579 "2020-11-05T12:01:33Z")

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I have a mixed system of equalities and inequalities, for example: x + 2y +3z = 10 2x + 4y + 10z = 20 4x + y + z \< 10 where unknown variables x, y, z are all real-valued. How can get a solution (or the range of all …

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## [ERROR: MethodError: no method matching PhysicsInformedNN(::Float64)](https://discourse.julialang.org/t/error-methoderror-no-method-matching-physicsinformednn-float64/49610)

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**Author:** [@BaoBaoDeMeng](https://discourse.julialang.org/u/BaoBaoDeMeng)\
**Replies:** 1\
**Last updated:** [November 5, 2020, 4:37am UTC](https://discourse.julialang.org/t/error-methoderror-no-method-matching-physicsinformednn-float64/49610 "2020-11-05T04:37:32Z")

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using Flux, DiffEqFluxModeling,ToolkitDiffEqBase, Plots, NeuralPDETest Example 1, 1D ode 1D ODE eq = Dt(u(t,θ)) ~ t^3 + 2t + (t^2)((1+3\*(t^2))/(1+t+(t^3))) - u(t,θ)(t + ((1+3(t^2))/(1+t+t^3))) Boundary conditions bc…

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## [CUDA.jl with missing data?](https://discourse.julialang.org/t/cuda-jl-with-missing-data/49563)

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**Author:** [@zlewko](https://discourse.julialang.org/u/zlewko)\
**Replies:** 4\
**Last updated:** [November 5, 2020, 2:06am UTC](https://discourse.julialang.org/t/cuda-jl-with-missing-data/49563 "2020-11-05T02:06:54Z")

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I’m trying to work with a dataset with missing data using the CUDA.jl. I’d like to skip the missing data in some statistics (mean, covariance etc). Is there any general solution to this that performs well on a GPU? I…

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## [CSV Error - Feather Error](https://discourse.julialang.org/t/csv-error-feather-error/49309)

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**Author:** [@orthoeng](https://discourse.julialang.org/u/orthoeng)\
**Replies:** 7\
**Last updated:** [November 4, 2020, 3:11pm UTC](https://discourse.julialang.org/t/csv-error-feather-error/49309 "2020-11-04T15:11:33Z")

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I’m very new to Julia Programming. I have a folder of CSV files (14) that I join to one big data frame and I’m trying to save the big CSV. (rows - 262673020 x columns - 77) when I use CSV.write - I get this ERROR: Bound…

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## [Proposal: working with larger than memory data in hdf5 format using HDF5Arrays (implementation of DiskArrays.jl for HDF5)](https://discourse.julialang.org/t/proposal-working-with-larger-than-memory-data-in-hdf5-format-using-hdf5arrays-implementation-of-diskarrays-jl-for-hdf5/48997)

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**Author:** [@Luapulu](https://discourse.julialang.org/u/Luapulu)\
**Replies:** 11\
**Last updated:** [November 4, 2020, 2:36pm UTC](https://discourse.julialang.org/t/proposal-working-with-larger-than-memory-data-in-hdf5-format-using-hdf5arrays-implementation-of-diskarrays-jl-for-hdf5/48997 "2020-11-04T14:36:21Z")

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Proposal Often, I have data, that is larger than memory and I’d like to be able to work with the hdf5 file format in julia. I propose we/I write a package (HDF5Arrays.jl) to address some of the following use cases (in ad…

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## [Plots.jl: Default label size](https://discourse.julialang.org/t/plots-jl-default-label-size/49454)

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**Author:** [@willtebbutt](https://discourse.julialang.org/u/willtebbutt)\
**Replies:** 3\
**Last updated:** [November 4, 2020, 1:45pm UTC](https://discourse.julialang.org/t/plots-jl-default-label-size/49454 "2020-11-04T13:45:13Z")

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Firstly, thanks for incorporating PGFPlotsX into Plots – it’s a really fantastic thing to have available. Looking through the tikz generated when I savefig, I notice that most of the font sizes are hard-coded to 8pt by …

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## [Local machine and Intranet DB up to date data formats - which one?](https://discourse.julialang.org/t/local-machine-and-intranet-db-up-to-date-data-formats-which-one/49557)

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**Author:** [@teriiju](https://discourse.julialang.org/u/teriiju)\
**Replies:** 0\
**Last updated:** [November 4, 2020, 12:01am UTC](https://discourse.julialang.org/t/local-machine-and-intranet-db-up-to-date-data-formats-which-one/49557 "2020-11-04T00:01:43Z")

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Hi, New to Julia : I would like to know what are the first 2 (or more) file formats recommanded to store data, strings/numbers (Multmedia support not needed): A) - for a local use, on standard workstation, if a txt t…

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## [Faces & Vertices of N Linear Constraints](https://discourse.julialang.org/t/faces-vertices-of-n-linear-constraints/49347)

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**Author:** [@anon92994695](https://discourse.julialang.org/u/anon92994695)\
**Replies:** 15\
**Last updated:** [November 3, 2020, 11:07pm UTC](https://discourse.julialang.org/t/faces-vertices-of-n-linear-constraints/49347 "2020-11-03T23:07:29Z")

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Here’s a fun one, so instead of doing what I normally do(hacking away at code), I figured I’d ask if people had tools to recommend for solving a problem. I know you people working in optimization and geometry live in thi…

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## [Convert a float into a string](https://discourse.julialang.org/t/convert-a-float-into-a-string/49513)

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**Author:** [@teriiju](https://discourse.julialang.org/u/teriiju)\
**Replies:** 25\
**Last updated:** [November 3, 2020, 10:26pm UTC](https://discourse.julialang.org/t/convert-a-float-into-a-string/49513 "2020-11-03T22:26:00Z")

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Hi, Is it possible to convert a float number into a string ? i.e. 32.234565 ()number into “32.234565” (string) or this works only with integers ? Thanks

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## [Implement Mixed Models with sparse X and Z matrices](https://discourse.julialang.org/t/implement-mixed-models-with-sparse-x-and-z-matrices/49539)

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**Author:** [@Antonina\_Klyuyeva](https://discourse.julialang.org/u/Antonina_Klyuyeva)\
**Replies:** 7\
**Last updated:** [November 3, 2020, 7:48pm UTC](https://discourse.julialang.org/t/implement-mixed-models-with-sparse-x-and-z-matrices/49539 "2020-11-03T19:48:53Z")

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Hi there, I use mixed models on a large file (500000 rows). My model formula looks like this: Y ~ 0 + num1:factor1 + num1:factor2 + num2:factor3 + factor4 + (0 + num3|subject) + (0 + num4|subject) + (1|subject), whe…

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