# Latest

**URL:** https://discourse.julialang.org/latest.md?page=969

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

**Page:** 970

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## [ODE solver slowed down by interpolation](https://discourse.julialang.org/t/ode-solver-slowed-down-by-interpolation/84913)

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**Author:** [@ap2013](https://discourse.julialang.org/u/ap2013)\
**Replies:** 1\
**Last updated:** [July 28, 2022, 12:04pm UTC](https://discourse.julialang.org/t/ode-solver-slowed-down-by-interpolation/84913 "2022-07-28T12:04:18Z")

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I have an ODE system defined through modelingtoolkit. The system is formed of multiple ODESystems and simplified with system = structural\_simplify(all). One of the ODESystem is defined by the following function functio…

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## [Washington DC Greater Metro Area meet up for JuliaCon 2022?](https://discourse.julialang.org/t/washington-dc-greater-metro-area-meet-up-for-juliacon-2022/82736)

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**Author:** [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Replies:** 24\
**Last updated:** [July 28, 2022, 11:57am UTC](https://discourse.julialang.org/t/washington-dc-greater-metro-area-meet-up-for-juliacon-2022/82736 "2022-07-28T11:57:15Z")

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Is anyone (@Nosferican ?) planning a meetup for DC and the surrounding area for JuliaCon 2022? I would be willing to help organize.

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## [Save and load the model generated by surrogates.jl](https://discourse.julialang.org/t/save-and-load-the-model-generated-by-surrogates-jl/83302)

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**Author:** [@Jack\_Tang](https://discourse.julialang.org/u/Jack_Tang)\
**Replies:** 4\
**Last updated:** [July 28, 2022, 10:31am UTC](https://discourse.julialang.org/t/save-and-load-the-model-generated-by-surrogates-jl/83302 "2022-07-28T10:31:58Z")

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Hello Community, How can I save and load the model generated by surrogates.jl?

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## [Constructing a list of options for a cmd](https://discourse.julialang.org/t/constructing-a-list-of-options-for-a-cmd/84910)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 4\
**Last updated:** [July 28, 2022, 10:08am UTC](https://discourse.julialang.org/t/constructing-a-list-of-options-for-a-cmd/84910 "2022-07-28T10:08:25Z")

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I have a list of options to pass to an executable. For the purposes of the MWE, a call could look like \`c\` \`c a=1\` \`c a=1 b=2\` Whether I need to append a and b are known at runtime, and are taken from a NamedTuple. N…

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## [Improve this function for merging tuples so that the return type could be accurately inferred](https://discourse.julialang.org/t/improve-this-function-for-merging-tuples-so-that-the-return-type-could-be-accurately-inferred/84893)

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**Author:** [@nsajko](https://discourse.julialang.org/u/nsajko)\
**Replies:** 1\
**Last updated:** [July 28, 2022, 6:57am UTC](https://discourse.julialang.org/t/improve-this-function-for-merging-tuples-so-that-the-return-type-could-be-accurately-inferred/84893 "2022-07-28T06:57:35Z")

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I implemented the function merged\_tuples for merging tuples in given order while preserving intra-tuple order. It seems that Julia isn’t able to infer the return types accurately, however (using Test.@inferred): julia\> …

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## [Number of points in Pareto front](https://discourse.julialang.org/t/number-of-points-in-pareto-front/84741)

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**Author:** [@chenr86](https://discourse.julialang.org/u/chenr86)\
**Replies:** 5\
**Last updated:** [July 28, 2022, 8:56am UTC](https://discourse.julialang.org/t/number-of-points-in-pareto-front/84741 "2022-07-28T08:56:11Z")

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Hello, I’m using MultiJuMP.jl to solve a MOO problem with 2 objectives, f1 and f2. Here, f1 is a continuous function to minimize, f2 is an integer function to maximize. When I post model.pointsperdim = 10, I got a pare…

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## [Overfitting when building kriging surrogate model](https://discourse.julialang.org/t/overfitting-when-building-kriging-surrogate-model/84857)

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**Author:** [@chenr86](https://discourse.julialang.org/u/chenr86)\
**Replies:** 6\
**Last updated:** [July 28, 2022, 7:37am UTC](https://discourse.julialang.org/t/overfitting-when-building-kriging-surrogate-model/84857 "2022-07-28T07:37:26Z")

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Hello, I’m using Surrogates.jl to build a surrogate model based on data in a CSV file. There are 24 input parameters and 1 output variables in my data. I have 500 samples. 80% samples are used for training set and other…

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## [Easier Solver Callback for JuMP.lj + Gurobi](https://discourse.julialang.org/t/easier-solver-callback-for-jump-lj-gurobi/84889)

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**Author:** [@chelseas](https://discourse.julialang.org/u/chelseas)\
**Replies:** 2\
**Last updated:** [July 28, 2022, 5:45am UTC](https://discourse.julialang.org/t/easier-solver-callback-for-jump-lj-gurobi/84889 "2022-07-28T05:45:49Z")

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I would like to write a callback function that does something similar to this: (gurobipy) but it seems much more complicated to do this in JuMP :frowning\_face:. see and here \[ANN\] Upcoming breaking changes to CPLE…

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## [Should Julia be a systems language?](https://discourse.julialang.org/t/should-julia-be-a-systems-language/84861)

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**Author:** [@kodintent](https://discourse.julialang.org/u/kodintent)\
**Replies:** 9\
**Last updated:** [July 28, 2022, 1:05am UTC](https://discourse.julialang.org/t/should-julia-be-a-systems-language/84861 "2022-07-28T01:05:30Z")

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This is a rather speculative post about Julia being used for building systems from scratch, as an alternative to ‘the C way’. Recently i spent some time learning Rust, as it infers it can be systems programming ‘for all…

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## [Update on future developement of BVP solvers?](https://discourse.julialang.org/t/update-on-future-developement-of-bvp-solvers/84839)

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**Author:** [@MButler](https://discourse.julialang.org/u/MButler)\
**Replies:** 6\
**Last updated:** [July 27, 2022, 11:47pm UTC](https://discourse.julialang.org/t/update-on-future-developement-of-bvp-solvers/84839 "2022-07-27T23:47:06Z")

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I’m currently doing research in gravitational physics and the problems I’m working with often end up as BVPs that are very stiff and sensitive to the initial conditions. It seems this is still a weak point for Julia’s BV…

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## [Better error messages: Invalid Comprehension syntax](https://discourse.julialang.org/t/better-error-messages-invalid-comprehension-syntax/84892)

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**Author:** [@Albert\_Zevelev](https://discourse.julialang.org/u/Albert_Zevelev)\
**Replies:** 3\
**Last updated:** [July 27, 2022, 10:14pm UTC](https://discourse.julialang.org/t/better-error-messages-invalid-comprehension-syntax/84892 "2022-07-27T22:14:13Z")

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Consider this syntax error: julia\> S1 = \[(.01 : .1 : 1.0);\]; julia\> S2 = \[(.01 : .1 : 1.0);\]; julia\> \[s1 +s2 for s1 in S1, s2 in S2\] ERROR: syntax: invalid comprehension syntax Stacktrace: \[1\] top-level scope @ no…

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## [How to undef a vector element](https://discourse.julialang.org/t/how-to-undef-a-vector-element/83427)

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**Author:** [@Joris\_Pinkse](https://discourse.julialang.org/u/Joris_Pinkse)\
**Replies:** 30\
**Last updated:** [July 27, 2022, 9:15pm UTC](https://discourse.julialang.org/t/how-to-undef-a-vector-element/83427 "2022-07-27T21:15:13Z")

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Suppose that I create an uninitialized vector of objects of type Stuff and then assign some content to it. At some point in the future, I no longer need a particular element and want the garbage collector to free up the…

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## [Future of Jill - Feedback session](https://discourse.julialang.org/t/future-of-jill-feedback-session/84894)

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**Author:** [@abelsiqueira](https://discourse.julialang.org/u/abelsiqueira)\
**Replies:** 0\
**Last updated:** [July 27, 2022, 9:15pm UTC](https://discourse.julialang.org/t/future-of-jill-feedback-session/84894 "2022-07-27T21:15:08Z")

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Hi all, As you may know, juliaup “will soon be announced as the official installer”, so it is a good time to question the future of alternative installers - in particular, the one I created: Jill¹ With that in mind, I …

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## [How to define Parameters locally in Sub julia files?](https://discourse.julialang.org/t/how-to-define-parameters-locally-in-sub-julia-files/84886)

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**Author:** [@Amro](https://discourse.julialang.org/u/Amro)\
**Replies:** 5\
**Last updated:** [July 27, 2022, 8:06pm UTC](https://discourse.julialang.org/t/how-to-define-parameters-locally-in-sub-julia-files/84886 "2022-07-27T20:06:30Z")

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Below is just an MWE for the concept (I am using dummy equations). I have main code in mani.jl which includes another file subi.jl. The main code calls function ini(args) to calculate mat which is useful only in functio…

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## [Symbolic function differentiation](https://discourse.julialang.org/t/symbolic-function-differentiation/84813)

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**Author:** [@Starpower\_Power](https://discourse.julialang.org/u/Starpower_Power)\
**Replies:** 2\
**Last updated:** [July 27, 2022, 7:46pm UTC](https://discourse.julialang.org/t/symbolic-function-differentiation/84813 "2022-07-27T19:46:51Z")

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in python sympy we define that x is function of t: x(t) and diff(x,t) is xdot x=sym.Function(‘x’)(t) how to do this thing in julia bcz i have to write Lagrangian equation

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## [Concrete typeof](https://discourse.julialang.org/t/concrete-typeof/84881)

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**Author:** [@nicolas](https://discourse.julialang.org/u/nicolas)\
**Replies:** 5\
**Last updated:** [July 27, 2022, 5:34pm UTC](https://discourse.julialang.org/t/concrete-typeof/84881 "2022-07-27T17:34:39Z")

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Is there a function to get the concrete (numeric) type of some object of abstract type without much information about it? Consider these two bad methods: using LinearAlgebra x = \[\[1,2\],\[3,4\]\] typeof(dot(x,x)) eltype(elt…

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## [In VSCode, "terminated with exit code: 139"](https://discourse.julialang.org/t/in-vscode-terminated-with-exit-code-139/84765)

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**Author:** [@fsmith001](https://discourse.julialang.org/u/fsmith001)\
**Replies:** 17\
**Last updated:** [July 27, 2022, 5:33pm UTC](https://discourse.julialang.org/t/in-vscode-terminated-with-exit-code-139/84765 "2022-07-27T17:33:56Z")

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Hello! I am trying out a function I have written to implement the power method. I am filling a CSRMatrix (a type created in the project I am working on) and then running my function with that matrix. I have no problems w…

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## [LibSerialPort problem on MacBook Pro](https://discourse.julialang.org/t/libserialport-problem-on-macbook-pro/81364)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 8\
**Last updated:** [July 27, 2022, 5:20pm UTC](https://discourse.julialang.org/t/libserialport-problem-on-macbook-pro/81364 "2022-07-27T17:20:28Z")

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I’m writing bytes to a serial port using LibSerialPort.jl. My code works on a Linux machine but not on a MacBook Pro. There are no errors, but the desired effect (a connected Arduino Nano Every lights up an LED on an LED…

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## [Issues claiming account on Discord](https://discourse.julialang.org/t/issues-claiming-account-on-discord/84882)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 4\
**Last updated:** [July 27, 2022, 5:15pm UTC](https://discourse.julialang.org/t/issues-claiming-account-on-discord/84882 "2022-07-27T17:15:32Z")

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I can login on Discord following the link, but cannot comment on the channels. I can only see the #welcome channel. When I try to claim my account it asks for a password, but I don’t remember my password for last year. T…

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## [Convert Dataframe column containing strings "A+", "A", "A-" ..."D+", "D", "D-" to integers 12,11,10 ... 3,2,1](https://discourse.julialang.org/t/convert-dataframe-column-containing-strings-a-a-a-d-d-d-to-integers-12-11-10-3-2-1/84849)

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**Author:** [@Nash](https://discourse.julialang.org/u/Nash)\
**Replies:** 9\
**Last updated:** [July 27, 2022, 2:30pm UTC](https://discourse.julialang.org/t/convert-dataframe-column-containing-strings-a-a-a-d-d-d-to-integers-12-11-10-3-2-1/84849 "2022-07-27T14:30:42Z")

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I have a dataframe where one of the columns is Grades. Grades contains strings for scores on the scale A+ to D-. How do I go about converting this information to integers instead on a 12-point scale (“A+” = 12, …, “D-” =…

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## [Parameter optimization of MethodOfLines PDE](https://discourse.julialang.org/t/parameter-optimization-of-methodoflines-pde/84647)

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**Author:** [@thompsonmj](https://discourse.julialang.org/u/thompsonmj)\
**Replies:** 10\
**Last updated:** [July 27, 2022, 2:35pm UTC](https://discourse.julialang.org/t/parameter-optimization-of-methodoflines-pde/84647 "2022-07-27T14:35:07Z")

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I’d like to optimize parameters in the MOL example shown here with an RMSD cost function to minimize. Following a WIP example here to build the OptimizationFunction, I have the following, but the results come back predi…

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## [How to update scalar and Boolean in-place?](https://discourse.julialang.org/t/how-to-update-scalar-and-boolean-in-place/84843)

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**Author:** [@Amro](https://discourse.julialang.org/u/Amro)\
**Replies:** 3\
**Last updated:** [July 27, 2022, 1:41pm UTC](https://discourse.julialang.org/t/how-to-update-scalar-and-boolean-in-place/84843 "2022-07-27T13:41:46Z")

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I have function update2 which returns the values of status, nChange. However, I need to build function update1 which update status, nChange without returning their values (in-place mutation) but it seems not correct proc…

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## [Using nlsolve for roots of Legendre Polynomials in terms of RadauIIA method](https://discourse.julialang.org/t/using-nlsolve-for-roots-of-legendre-polynomials-in-terms-of-radauiia-method/84872)

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**Author:** [@Vick](https://discourse.julialang.org/u/Vick)\
**Replies:** 0\
**Last updated:** [July 27, 2022, 1:04pm UTC](https://discourse.julialang.org/t/using-nlsolve-for-roots-of-legendre-polynomials-in-terms-of-radauiia-method/84872 "2022-07-27T13:04:31Z")

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Hi, I need to find root for Legendre polynomials in terms of the RadauIIA method using ClassicalOrthogonalPolynomials, NLsolve function P(x, n) return legendrep(n, x) end function radc(x, s) v = 2 \* x - 1 …

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## [Flux: can't get recurrent sequence-to-one model to train](https://discourse.julialang.org/t/flux-cant-get-recurrent-sequence-to-one-model-to-train/57459)

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**Author:** [@mcreel](https://discourse.julialang.org/u/mcreel)\
**Replies:** 8\
**Last updated:** [July 27, 2022, 1:18pm UTC](https://discourse.julialang.org/t/flux-cant-get-recurrent-sequence-to-one-model-to-train/57459 "2022-07-27T13:18:08Z")

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I am attempting to create a simple recurrent model that takes data generated by a parameterized data generating process as the input, and the parameters of the DGP as the output. The goal is to learn the parameters, give…

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## [Bar and line charts combined in PlotlyJS](https://discourse.julialang.org/t/bar-and-line-charts-combined-in-plotlyjs/84870)

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**Author:** [@Mariana](https://discourse.julialang.org/u/Mariana)\
**Replies:** 2\
**Last updated:** [July 27, 2022, 12:55pm UTC](https://discourse.julialang.org/t/bar-and-line-charts-combined-in-plotlyjs/84870 "2022-07-27T12:55:40Z")

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Hello! I’m trying to plot a bar chart and a line chart combined in the same double y-axis plot, using PlotlyJS, by running the following code: fixed\_cost = \[791.57;773.16;765.58;758.15;750.86;743.71;736.69;729.81;723.0…

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## [Iterative proportional fitting package?](https://discourse.julialang.org/t/iterative-proportional-fitting-package/60580)

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**Author:** [@amrods](https://discourse.julialang.org/u/amrods)\
**Replies:** 4\
**Last updated:** [July 27, 2022, 10:49am UTC](https://discourse.julialang.org/t/iterative-proportional-fitting-package/60580 "2022-07-27T10:49:25Z")

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Is there any package that implements the iterative proportional fitting procedure?

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## [Iterate fitting linear model and extract coefficients over grouped DataFrame](https://discourse.julialang.org/t/iterate-fitting-linear-model-and-extract-coefficients-over-grouped-dataframe/84814)

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**Author:** [@guysutton](https://discourse.julialang.org/u/guysutton)\
**Replies:** 4\
**Last updated:** [July 27, 2022, 10:45am UTC](https://discourse.julialang.org/t/iterate-fitting-linear-model-and-extract-coefficients-over-grouped-dataframe/84814 "2022-07-27T10:45:44Z")

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I am trying to iteratively fit many models (e.g. a linear model \[GLM.jl\] or mixed model \[MixedModels.jl\]) to a DataFrame, whereby a new model is fit to each level of a grouping column. For example: if I wanted to fit one…

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## [Vcat row vectors -\> matrix?](https://discourse.julialang.org/t/vcat-row-vectors-matrix/84623)

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**Author:** [@ryofurue](https://discourse.julialang.org/u/ryofurue)\
**Replies:** 10\
**Last updated:** [July 27, 2022, 10:39am UTC](https://discourse.julialang.org/t/vcat-row-vectors-matrix/84623 "2022-07-27T10:39:16Z")

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Say, you want a 2 x 3 matrix from two 3-element row vectors. The simplest way I can think of currently is a = \[1, 2, 3\] b = \[10,20,30\] m2x3 = transpose(hcat(a,b)) This isn’t bad at all, but I thought the right way woul…

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## [What does a ReadOnlyMemoryError mean?](https://discourse.julialang.org/t/what-does-a-readonlymemoryerror-mean/84809)

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**Author:** [@Impressium](https://discourse.julialang.org/u/Impressium)\
**Replies:** 1\
**Last updated:** [July 26, 2022, 11:36am UTC](https://discourse.julialang.org/t/what-does-a-readonlymemoryerror-mean/84809 "2022-07-26T11:36:57Z")

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Hi all :slight\_smile: I use pycall to get data from Snowflake. But sometimes I get a ReadOnlyMemoryError error. What does that mean and how to prevent it? ReadOnlyMemoryError() Stacktrace: \[1\] macro expansion @ C…

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## [Is it possible for "ccall" to call the shared library created by PackageCompiler.jl?](https://discourse.julialang.org/t/is-it-possible-for-ccall-to-call-the-shared-library-created-by-packagecompiler-jl/84298)

<div class="topic-metadata">

**Author:** [@lionisxn](https://discourse.julialang.org/u/lionisxn)\
**Replies:** 53\
**Last updated:** [July 27, 2022, 6:26am UTC](https://discourse.julialang.org/t/is-it-possible-for-ccall-to-call-the-shared-library-created-by-packagecompiler-jl/84298 "2022-07-27T06:26:03Z")

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I am trying to create a .dll that can be called by other languages, e.g. MATLAB or C. I just test the example given in “PackageCompiler.jl”, and generate the following file bundles where “fist\_lib\_wy.dll” is the created …

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