# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=358

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**Page:** 359

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## [LinearAlgebra eigensolver convergence issues around nearby eigenvalues](https://discourse.julialang.org/t/linearalgebra-eigensolver-convergence-issues-around-nearby-eigenvalues/62775)

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**Author:** [@vivian-rogers](https://discourse.julialang.org/u/vivian-rogers)\
**Replies:** 5\
**Last updated:** [June 14, 2021, 9:49am UTC](https://discourse.julialang.org/t/linearalgebra-eigensolver-convergence-issues-around-nearby-eigenvalues/62775 "2021-06-14T09:49:37Z")

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(Plotted above is the eigenvalues of a matrix A(k), with k being momentum on the x axis). Hi, So I am trying to get the eigenvalues and eigenvectors of a hermitian matrix that continuously depends on a parameter k, w…

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## [List comprehension of JuMP variables](https://discourse.julialang.org/t/list-comprehension-of-jump-variables/62848)

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**Author:** [@anon94806364](https://discourse.julialang.org/u/anon94806364)\
**Replies:** 8\
**Last updated:** [June 14, 2021, 5:42am UTC](https://discourse.julialang.org/t/list-comprehension-of-jump-variables/62848 "2021-06-14T05:42:03Z")

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Beginner to Julia and want to quickly recapitulate an ILP model I wrote in Python to evaluate speed in JuMP. I’m wondering how list comprehensions work for JuMP objects? In Python, I use list comprehension to make the …

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## [BoundsError: attempt to access 2-element Vector in DDPG algorithm](https://discourse.julialang.org/t/boundserror-attempt-to-access-2-element-vector-in-ddpg-algorithm/62574)

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**Author:** [@GK\_197](https://discourse.julialang.org/u/GK_197)\
**Replies:** 1\
**Last updated:** [June 14, 2021, 4:21am UTC](https://discourse.julialang.org/t/boundserror-attempt-to-access-2-element-vector-in-ddpg-algorithm/62574 "2021-06-14T04:21:05Z")

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Hi, I was implementing DDPG algorithm for 1-D vector action space but, during run it shows error as: BoundsError: attempt to access 2-element Vector{Float64} at index \[\] Now, when looked into DDPG policy on Github # …

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## [Compute frequency or proportions on grouped dataframes](https://discourse.julialang.org/t/compute-frequency-or-proportions-on-grouped-dataframes/62835)

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**Author:** [@vjd](https://discourse.julialang.org/u/vjd)\
**Replies:** 10\
**Last updated:** [June 14, 2021, 12:20am UTC](https://discourse.julialang.org/t/compute-frequency-or-proportions-on-grouped-dataframes/62835 "2021-06-14T00:20:53Z")

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I would like to learn all possible ways of summarizing categorical data using the dataframes ecosystem. Preferably, I would like to compute the 1) frequency 2) proportions of each categorical variable after a grouping o…

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## [Silly question regarding vectorized syntax \[JUMP\]](https://discourse.julialang.org/t/silly-question-regarding-vectorized-syntax-jump/62853)

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**Author:** [@Jameli](https://discourse.julialang.org/u/Jameli)\
**Replies:** 2\
**Last updated:** [June 14, 2021, 12:16am UTC](https://discourse.julialang.org/t/silly-question-regarding-vectorized-syntax-jump/62853 "2021-06-14T00:16:08Z")

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Hello everyone! I’m having some trouble with some basic concepts about vectorized syntax. My data were structured this way (just to show that everything is in matrix form): U = \[ ATumor zeros(tr, tr) zeros(tr, g…

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## [Does JuMP work well with vectorized data?](https://discourse.julialang.org/t/does-jump-work-well-with-vectorized-data/62852)

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**Author:** [@Jameli](https://discourse.julialang.org/u/Jameli)\
**Replies:** 1\
**Last updated:** [June 13, 2021, 11:19pm UTC](https://discourse.julialang.org/t/does-jump-work-well-with-vectorized-data/62852 "2021-06-13T23:19:29Z")

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Hello, everyone! Greetings from Brazil! I’ve come from MATLAB in order to gain some speed regarding LP’s problems. And searching about JuMP, I found this topic Memory consumption and time of @constraint · Issue #969 · j…

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## [Gibbs sampling with Gen.jl or best ppl for complicated model](https://discourse.julialang.org/t/gibbs-sampling-with-gen-jl-or-best-ppl-for-complicated-model/62466)

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**Author:** [@EvoArt](https://discourse.julialang.org/u/EvoArt)\
**Replies:** 2\
**Last updated:** [June 13, 2021, 10:50pm UTC](https://discourse.julialang.org/t/gibbs-sampling-with-gen-jl-or-best-ppl-for-complicated-model/62466 "2021-06-13T22:50:59Z")

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I’m trying to implement a model, described here. It requires Langevin MC, spike slab priors and Gibbs steps. of the Julia PPLs, Gen.jl seems like the best fit overall, due to the flexibility of building your own sampling…

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## [API documentation for gurobi.jl](https://discourse.julialang.org/t/api-documentation-for-gurobi-jl/62825)

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**Author:** [@anon94806364](https://discourse.julialang.org/u/anon94806364)\
**Replies:** 4\
**Last updated:** [June 13, 2021, 10:04pm UTC](https://discourse.julialang.org/t/api-documentation-for-gurobi-jl/62825 "2021-06-13T22:04:08Z")

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I’ve been trying to solve an ILP in Python where the primary bottle neck appears to be model construction. Multiple sources cite that model construction is heavily language dependent (whereas the optimization is language…

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## [Manifold optimization with additional constraints](https://discourse.julialang.org/t/manifold-optimization-with-additional-constraints/62799)

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**Author:** [@Jae-Mo\_Lihm](https://discourse.julialang.org/u/Jae-Mo_Lihm)\
**Replies:** 1\
**Last updated:** [June 13, 2021, 9:53pm UTC](https://discourse.julialang.org/t/manifold-optimization-with-additional-constraints/62799 "2021-06-13T21:53:25Z")

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I want to minimize f(x), with two constraints: (1) x is a unitary matrix, and (2) f\_i(x) \>= 0 for i=1, …, N. (In my case, f\_i(x) are quadratic functions, e.g. abs(x\[1, 1\])^2) - 0.5. Because of the unitarity constraint, …

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## [How to tackle 2D reaction-diffusion equation?](https://discourse.julialang.org/t/how-to-tackle-2d-reaction-diffusion-equation/54110)

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**Author:** [@gedankenexperiment](https://discourse.julialang.org/u/gedankenexperiment)\
**Replies:** 19\
**Last updated:** [June 13, 2021, 8:16pm UTC](https://discourse.julialang.org/t/how-to-tackle-2d-reaction-diffusion-equation/54110 "2021-06-13T20:16:40Z")

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Can anyone point me in the right direction of how to solve a 2D reaction-diffusion equation of the following kind: p-d\*c=-D \* (d^2/dx^2 + d^2/dy^2) \* c, where p is the production rate, d the degradation rate, c the con…

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## [How to compute gradient with respect to a circuit parameter?](https://discourse.julialang.org/t/how-to-compute-gradient-with-respect-to-a-circuit-parameter/61706)

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**Author:** [@rmedinar](https://discourse.julialang.org/u/rmedinar)\
**Replies:** 6\
**Last updated:** [June 13, 2021, 1:21pm UTC](https://discourse.julialang.org/t/how-to-compute-gradient-with-respect-to-a-circuit-parameter/61706 "2021-06-13T13:21:33Z")

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Hi everyone! I’m trying to compute the gradient with respect to a certain circuit parameter and I would like to do it efficiently. I know there exist several efficient methods for this in Yao, i.e., faithful\_grad() and …

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## [Finding Item in Dict](https://discourse.julialang.org/t/finding-item-in-dict/62814)

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**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 4\
**Last updated:** [June 13, 2021, 7:47am UTC](https://discourse.julialang.org/t/finding-item-in-dict/62814 "2021-06-13T07:47:48Z")

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I’m trying to add a new value to data tables in a dictionary, but when I run this. using DataFrames general\_ledger=Dict( "dividends" =\> DataFrame( date=Vector{String}(), …

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## [Cannot show plot with pgfplots backend](https://discourse.julialang.org/t/cannot-show-plot-with-pgfplots-backend/19170)

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**Author:** [@vietspaceanh](https://discourse.julialang.org/u/vietspaceanh)\
**Replies:** 0\
**Last updated:** [January 1, 2019, 7:54pm UTC](https://discourse.julialang.org/t/cannot-show-plot-with-pgfplots-backend/19170 "2019-01-01T19:54:46Z")

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When I try a simple plot with pgfplots backend with the following code: using Plots pgfplots() plot(rand(10)) I got the following error: Error showing value of type Plots.Plot{Plots.PGFPlotsBackend}: ERROR: SystemEr…

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## [Append to JuliaDB tables in a Dict](https://discourse.julialang.org/t/append-to-juliadb-tables-in-a-dict/62809)

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**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 0\
**Last updated:** [June 12, 2021, 7:49pm UTC](https://discourse.julialang.org/t/append-to-juliadb-tables-in-a-dict/62809 "2021-06-12T19:49:39Z")

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I have this dictionary on nsparce tables. general\_ledger=Dict( #:description =\> ndsparse(date=date, memo=memo), :dividends =\> ndsparse((debit=x, credit=y), (balance=z,)), :expenses =\> ndspars…

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## [Updating Julia has broken scatter plots](https://discourse.julialang.org/t/updating-julia-has-broken-scatter-plots/62712)

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**Author:** [@scotts](https://discourse.julialang.org/u/scotts)\
**Replies:** 6\
**Last updated:** [June 12, 2021, 4:13pm UTC](https://discourse.julialang.org/t/updating-julia-has-broken-scatter-plots/62712 "2021-06-12T16:13:56Z")

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After recently updating Julia from 1.4 to 1.6 I’ve found I can’t display data in scatter plots. Plots works fine for standard line charts, but using scatter(x,y) or plot(x,y,seriestype=:scatter) both just display axes w…

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## [How to avoid instability in DifferentialEquations?](https://discourse.julialang.org/t/how-to-avoid-instability-in-differentialequations/62739)

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**Author:** [@Luigi\_Marongiu](https://discourse.julialang.org/u/Luigi_Marongiu)\
**Replies:** 3\
**Last updated:** [June 12, 2021, 12:06pm UTC](https://discourse.julialang.org/t/how-to-avoid-instability-in-differentialequations/62739 "2021-06-12T12:06:01Z")

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Hello, I am trying to model the interaction between bacteria and phages but using certain combinations of parameters (namely the time and amount of phage inoculum) I get instability and the integrator aborts the session…

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## [The plot command moves the graph](https://discourse.julialang.org/t/the-plot-command-moves-the-graph/62161)

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**Author:** [@Paolo\_Jara](https://discourse.julialang.org/u/Paolo_Jara)\
**Replies:** 11\
**Last updated:** [June 12, 2021, 3:32am UTC](https://discourse.julialang.org/t/the-plot-command-moves-the-graph/62161 "2021-06-12T03:32:45Z")

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Hello, I’m new programming in Julia. I have two queries regarding the Plots package. (i) Is there a way to integrate the colors generated by “distinguishable\_colors (10)” into the scatter below? (ii) Do you know why the …

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## [Binning polar values with Julia](https://discourse.julialang.org/t/binning-polar-values-with-julia/62754)

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**Author:** [@danrib07](https://discourse.julialang.org/u/danrib07)\
**Replies:** 7\
**Last updated:** [June 11, 2021, 10:53pm UTC](https://discourse.julialang.org/t/binning-polar-values-with-julia/62754 "2021-06-11T22:53:00Z")

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Hello, I have to bin periodic data. I was wondering if there are packages that can deal with polar binning in Julia. I have not been able to find it online. Any help is appreciated! Thank you in advance!

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## [Unsatisfiable for CUDA](https://discourse.julialang.org/t/unsatisfiable-for-cuda/52355)

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**Author:** [@basernapairs](https://discourse.julialang.org/u/basernapairs)\
**Replies:** 1\
**Last updated:** [June 11, 2021, 7:38pm UTC](https://discourse.julialang.org/t/unsatisfiable-for-cuda/52355 "2021-06-11T19:38:43Z")

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I want to try Yao quantum, but CUDA unsatisfiable me

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## [Cross product with CUDA.jl](https://discourse.julialang.org/t/cross-product-with-cuda-jl/62734)

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**Author:** [@lodygaw](https://discourse.julialang.org/u/lodygaw)\
**Replies:** 2\
**Last updated:** [June 11, 2021, 4:31pm UTC](https://discourse.julialang.org/t/cross-product-with-cuda-jl/62734 "2021-06-11T16:31:53Z")

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Hello, I am looking for the way to compute cross product on a GPU. Basically something similar to this: function cross(w::CuArray{Float32,1}, u::CuArray{Float32,1}, v::CuArray{Float32,1}) w\[1\] = u\[2\] \* v\[3\] - u\[3\] \* v…

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## [Store graph adjacency lists on GPU](https://discourse.julialang.org/t/store-graph-adjacency-lists-on-gpu/62735)

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**Author:** [@aswanthkrishna](https://discourse.julialang.org/u/aswanthkrishna)\
**Replies:** 0\
**Last updated:** [June 11, 2021, 12:43pm UTC](https://discourse.julialang.org/t/store-graph-adjacency-lists-on-gpu/62735 "2021-06-11T12:43:39Z")

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I want to represent a adjacency list of a graph on GPU. I need to store the adjacency list and access neighbours of different nodes from the kernel efficiently. how can i do this? I am new to julia and CUDA. Any pointers…

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## [Physics World Quantum Week](https://discourse.julialang.org/t/physics-world-quantum-week/62721)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 0\
**Last updated:** [June 11, 2021, 7:39am UTC](https://discourse.julialang.org/t/physics-world-quantum-week/62721 "2021-06-11T07:39:56Z")

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Physics World magazine is organising a week of Quantum themed webinars. (scroll down the page a little)

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## [Secure hashing algorithm in Julia for passwords](https://discourse.julialang.org/t/secure-hashing-algorithm-in-julia-for-passwords/19913)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 8\
**Last updated:** [January 23, 2019, 10:40pm UTC](https://discourse.julialang.org/t/secure-hashing-algorithm-in-julia-for-passwords/19913 "2019-01-23T22:40:02Z")

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Is there an algorithm implemented in Julia for the purpose of hashing passwords? In Go, I used to use the bcrypt package which implements Provos and Mazières’s bcrypt adaptive hashing algorithm I want to do this for the…

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## [Generate structured problem matrices](https://discourse.julialang.org/t/generate-structured-problem-matrices/62688)

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**Author:** [@matthiasbe](https://discourse.julialang.org/u/matthiasbe)\
**Replies:** 1\
**Last updated:** [June 10, 2021, 11:07pm UTC](https://discourse.julialang.org/t/generate-structured-problem-matrices/62688 "2021-06-10T23:07:04Z")

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Hello, I am studying the low rank approximations of matrices, for example by truncated the Singular Value Decomposition of a matrix. In order to test any algorithm, I need some test matrices that have internal structur…

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## [GPUs for Neural ODEs](https://discourse.julialang.org/t/gpus-for-neural-odes/62697)

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**Author:** [@quantiota](https://discourse.julialang.org/u/quantiota)\
**Replies:** 2\
**Last updated:** [June 10, 2021, 10:28pm UTC](https://discourse.julialang.org/t/gpus-for-neural-odes/62697 "2021-06-10T22:28:04Z")

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Hey I am building a GPU server, I have the possibility to buy 8 tesla k80 GDDR5 24GB for $300 each. Is it good for training a Neural ODE Network. Thanks

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## [Computing sparse orthogonal projections](https://discourse.julialang.org/t/computing-sparse-orthogonal-projections/62652)

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**Author:** [@Thomas](https://discourse.julialang.org/u/Thomas)\
**Replies:** 6\
**Last updated:** [June 10, 2021, 4:01pm UTC](https://discourse.julialang.org/t/computing-sparse-orthogonal-projections/62652 "2021-06-10T16:01:44Z")

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Follow up question: since this is part of my implementation of the projection matrix A\*inv(A'A)\*A' do you see a fast way to stay within SparseMatrixCSC? Working implementation but not sparse project(A::SparseMatrixCSC,…

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## [Plotting data on a map in Julia](https://discourse.julialang.org/t/plotting-data-on-a-map-in-julia/4655)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 8\
**Last updated:** [June 10, 2021, 2:45pm UTC](https://discourse.julialang.org/t/plotting-data-on-a-map-in-julia/4655 "2021-06-10T14:45:40Z")

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Is there any way to plot data with latitude/longitude on a map in Julia? I am used to folium in Python and ggmap in R: https://github.com/python-visualization/folium https://github.com/dkahle/ggmap but I am trying to…

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## [Selecting best DAG from the family of DAGs based on AIC score](https://discourse.julialang.org/t/selecting-best-dag-from-the-family-of-dags-based-on-aic-score/62611)

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**Author:** [@ashwanimalviya](https://discourse.julialang.org/u/ashwanimalviya)\
**Replies:** 6\
**Last updated:** [June 10, 2021, 6:11am UTC](https://discourse.julialang.org/t/selecting-best-dag-from-the-family-of-dags-based-on-aic-score/62611 "2021-06-10T06:11:46Z")

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Thank you @Jeff Erlich for your suggestion to post my question on discourse. I would like to say to the Julia community here, I have posted a question(In the link) and have one more block regarding this Slack issue. I h…

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## [Problems in the Gurobi installation](https://discourse.julialang.org/t/problems-in-the-gurobi-installation/62630)

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**Author:** [@angeloaliano1](https://discourse.julialang.org/u/angeloaliano1)\
**Replies:** 7\
**Last updated:** [June 9, 2021, 3:54pm UTC](https://discourse.julialang.org/t/problems-in-the-gurobi-installation/62630 "2021-06-09T15:54:52Z")

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Dear all, I have the Gurobi software on my computer. I want to install the Gurobi package in Julia. I have followed the steps on GitHub - jump-dev/Gurobi.jl: Julia interface for Gurobi Optimizer An error message appea…

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## [How to sample from a truncated distribution given a certain known variance?](https://discourse.julialang.org/t/how-to-sample-from-a-truncated-distribution-given-a-certain-known-variance/62618)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 2\
**Last updated:** [June 9, 2021, 3:43pm UTC](https://discourse.julialang.org/t/how-to-sample-from-a-truncated-distribution-given-a-certain-known-variance/62618 "2021-06-09T15:43:59Z")

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I did notice that when I sample from a truncated distribution the sample variance I get is not the one that I would expect from the distribution, but one “corrected” by the truncation process: using Distributions, Stati…

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