# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=528

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**Page:** 529

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## [Finding jumps/discontinuities in a univariate function](https://discourse.julialang.org/t/finding-jumps-discontinuities-in-a-univariate-function/13919)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 4\
**Last updated:** [August 23, 2018, 8:20am UTC](https://discourse.julialang.org/t/finding-jumps-discontinuities-in-a-univariate-function/13919 "2018-08-23T08:20:32Z")

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I want to find jumps (or at least one jump, if it exists) in a univariate function on a given interval. Eg looking for a jump in f(x) = x \> 0 ? one(x) : zero(x) on \[-2,2\] should give me \\approx 0. I searched the liter…

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## [Singular Exceptions on Windows OS](https://discourse.julialang.org/t/singular-exceptions-on-windows-os/13877)

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**Author:** [@HSFengWang](https://discourse.julialang.org/u/HSFengWang)\
**Replies:** 9\
**Last updated:** [August 23, 2018, 8:14am UTC](https://discourse.julialang.org/t/singular-exceptions-on-windows-os/13877 "2018-08-23T08:14:50Z")

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When I use LsqFit to loop some curve fitting, I come across some singular exceptions. Anyone could give me some guidance on this problem. My os is window 32. Thank you. func(x, p) = 1 ./ (p\[1\]+p\[2\] \* exp.(-p\[3\] \* x ))…

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## [Slight change in an equation brings Domain error with mcpSolve](https://discourse.julialang.org/t/slight-change-in-an-equation-brings-domain-error-with-mcpsolve/13881)

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**Author:** [@axelle](https://discourse.julialang.org/u/axelle)\
**Replies:** 0\
**Last updated:** [August 22, 2018, 1:04pm UTC](https://discourse.julialang.org/t/slight-change-in-an-equation-brings-domain-error-with-mcpsolve/13881 "2018-08-22T13:04:51Z")

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Good afternoon, I have a system of equations and keep getting “domain error” for some values of the parameters. I have been able to solve a lot of them. For instance, I had some difficulties with some integral that were…

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## [Calculating bandstructure of graphene](https://discourse.julialang.org/t/calculating-bandstructure-of-graphene/13766)

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**Author:** [@Janis\_Erdmanis](https://discourse.julialang.org/u/Janis_Erdmanis)\
**Replies:** 24\
**Last updated:** [August 22, 2018, 8:38pm UTC](https://discourse.julialang.org/t/calculating-bandstructure-of-graphene/13766 "2018-08-22T20:38:02Z")

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Looking on github I see that there are some packages in Julia which are tagged with density functional theory (DFT). I wonder, if any of them can be used for calculating band-structure of graphene (for example figure 3 i…

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## [Question About Transposes and Matrix Multiplication Speed](https://discourse.julialang.org/t/question-about-transposes-and-matrix-multiplication-speed/13870)

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**Author:** [@Juser](https://discourse.julialang.org/u/Juser)\
**Replies:** 9\
**Last updated:** [August 22, 2018, 6:00pm UTC](https://discourse.julialang.org/t/question-about-transposes-and-matrix-multiplication-speed/13870 "2018-08-22T18:00:48Z")

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I’ve noticed that for Julia 0.7.0 that A\*c is faster than A'\*c in the following case, when I would have expected that A' would make the align the memory more easily for the computer to perform the matrix multiplication. …

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## [Trying to plot freezes Julia?](https://discourse.julialang.org/t/trying-to-plot-freezes-julia/13879)

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**Author:** [@HelgavonLichtenstein](https://discourse.julialang.org/u/HelgavonLichtenstein)\
**Replies:** 17\
**Last updated:** [August 22, 2018, 2:58pm UTC](https://discourse.julialang.org/t/trying-to-plot-freezes-julia/13879 "2018-08-22T14:58:22Z")

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Hello, I am trying to create a plot using Plots.jl and have run some code but it has already been over 15 minutes with no response from Julia. The screen looks like: Is this normal? It seems unusual to me. I am using…

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## [DFO algorithms for constrained optimization](https://discourse.julialang.org/t/dfo-algorithms-for-constrained-optimization/13882)

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**Author:** [@ivborissov](https://discourse.julialang.org/u/ivborissov)\
**Replies:** 0\
**Last updated:** [August 22, 2018, 1:32pm UTC](https://discourse.julialang.org/t/dfo-algorithms-for-constrained-optimization/13882 "2018-08-22T13:32:27Z")

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Hi, could you please recommend me “free” solvers/algorithms for derivative-free optimization which support inequality/equality and bound constraints. Currently I use AUGLAG from NLopt with NELDERMEAD,SBPLX or BOBYQA as l…

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## [@NLconstraint not working with splatting syntax](https://discourse.julialang.org/t/nlconstraint-not-working-with-splatting-syntax/13796)

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**Author:** [@Arrigo\_Benedetti](https://discourse.julialang.org/u/Arrigo_Benedetti)\
**Replies:** 2\
**Last updated:** [August 22, 2018, 7:02am UTC](https://discourse.julialang.org/t/nlconstraint-not-working-with-splatting-syntax/13796 "2018-08-22T07:02:01Z")

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I am trying to solve a constrained non linear optimization problem with JuMP/Ipopt and since the cost function and the constraint are functions of vector variables, I am using the splatting syntax as suggested in the JuM…

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## [Force describe() not to omit columns](https://discourse.julialang.org/t/force-describe-not-to-omit-columns/13793)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 7\
**Last updated:** [August 21, 2018, 10:06pm UTC](https://discourse.julialang.org/t/force-describe-not-to-omit-columns/13793 "2018-08-21T22:06:42Z")

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is it possible to force describe not to omit columns for printing?

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## [Dataframe functional input and output formats in julia 1.0, august 2018](https://discourse.julialang.org/t/dataframe-functional-input-and-output-formats-in-julia-1-0-august-2018/13800)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 2\
**Last updated:** [August 21, 2018, 5:58pm UTC](https://discourse.julialang.org/t/dataframe-functional-input-and-output-formats-in-julia-1-0-august-2018/13800 "2018-08-21T17:58:51Z")

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I am trying to find out in what data formats Julia 1.0 can currently \[august 2018\] use to read and write data frames. for a sample, I am using something simple like julia\> df 6×4 DataFrame │ Row │ n1 │ n2 │ n3 …

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## [Dynamically adding constraints with @constraintref](https://discourse.julialang.org/t/dynamically-adding-constraints-with-constraintref/13830)

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**Author:** [@mm0063](https://discourse.julialang.org/u/mm0063)\
**Replies:** 1\
**Last updated:** [August 21, 2018, 1:24pm UTC](https://discourse.julialang.org/t/dynamically-adding-constraints-with-constraintref/13830 "2018-08-21T13:24:38Z")

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Dear all, I am trying to dynamically add constraints to my model as in the example below. However, this formulation results in the error stated below the formulation. I believe that the problem occurs due to the \[t in t…

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## [LLVM crash when running Flux and CuArray examples in julia 0.7](https://discourse.julialang.org/t/llvm-crash-when-running-flux-and-cuarray-examples-in-julia-0-7/12967)

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**Author:** [@rkat](https://discourse.julialang.org/u/rkat)\
**Replies:** 13\
**Last updated:** [August 21, 2018, 7:07am UTC](https://discourse.julialang.org/t/llvm-crash-when-running-flux-and-cuarray-examples-in-julia-0-7/12967 "2018-08-21T07:07:12Z")

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I’m running on Ubuntu 16.04 with a Quadro K1200. I’m able to build and run all of the NVIDIA CUDA examples, but I can’t seem to get Flux/CuArrays working. I’m using julia 0.7 which is not well supported by Flux and CuArr…

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## [How to make Julia use AVX2 instructions?](https://discourse.julialang.org/t/how-to-make-julia-use-avx2-instructions/13797)

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**Author:** [@YingboMa](https://discourse.julialang.org/u/YingboMa)\
**Replies:** 1\
**Last updated:** [August 21, 2018, 3:44am UTC](https://discourse.julialang.org/t/how-to-make-julia-use-avx2-instructions/13797 "2018-08-21T03:44:30Z")

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How can I make Julia use AVX2 instructions for the following code? kc = 2 Ac = rand(4\*kc) Bc = rand(kc\*4) AB = zeros(4\*4) function micro\_ker!(AB, Ac, Bc, kc::Int, offsetA::Int, offsetB::Int) MR = 4 NR = 4 fi…

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## [A prototype for a minimalistic universal database API](https://discourse.julialang.org/t/a-prototype-for-a-minimalistic-universal-database-api/13743)

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**Author:** [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Replies:** 4\
**Last updated:** [August 20, 2018, 5:19pm UTC](https://discourse.julialang.org/t/a-prototype-for-a-minimalistic-universal-database-api/13743 "2018-08-20T17:19:44Z")

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Hello all, I have written an extremely minimal universal database API in the style of PEP249. It is so minimal, in fact, that by design you should not even have to import this package to implement it. My goal was to pr…

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## [Distributed for loop slower than serial?](https://discourse.julialang.org/t/distributed-for-loop-slower-than-serial/13722)

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**Author:** [@Panadestein](https://discourse.julialang.org/u/Panadestein)\
**Replies:** 4\
**Last updated:** [August 20, 2018, 7:28am UTC](https://discourse.julialang.org/t/distributed-for-loop-slower-than-serial/13722 "2018-08-20T07:28:07Z")

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Hello everyone. As the title of this post says, I have been trying to parallelize a for loop that is included in one of the programs I’m developing for my PhD thesis. This code was originally written in Python, but at so…

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## [No overflow nor underflow rounding mode for Floats](https://discourse.julialang.org/t/no-overflow-nor-underflow-rounding-mode-for-floats/12487)

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**Author:** [@milankl](https://discourse.julialang.org/u/milankl)\
**Replies:** 6\
**Last updated:** [August 19, 2018, 3:51pm UTC](https://discourse.julialang.org/t/no-overflow-nor-underflow-rounding-mode-for-floats/12487 "2018-08-19T15:51:40Z")

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Hey there, I see from the manual that different rounding modes for floats exist. However, I was wondering whether there is a smart way to set or emulate a rounding mode that is similar to RoundNearest, but without overf…

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## [Domain Troubles with Differential Equations Solver (with non-auto-differentiable function inside the ODE def)](https://discourse.julialang.org/t/domain-troubles-with-differential-equations-solver-with-non-auto-differentiable-function-inside-the-ode-def/13650)

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**Author:** [@shoshievass](https://discourse.julialang.org/u/shoshievass)\
**Replies:** 33\
**Last updated:** [August 19, 2018, 12:26pm UTC](https://discourse.julialang.org/t/domain-troubles-with-differential-equations-solver-with-non-auto-differentiable-function-inside-the-ode-def/13650 "2018-08-19T12:26:26Z")

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I’m trying to solve an ODE that uses a non-auto-differentiable function inside its definition (in particular, I solve a constrained quadratic program with JuMP to define du/dt in each iteration). In principle, the soluti…

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## [Logabsdet(singular)](https://discourse.julialang.org/t/logabsdet-singular/13706)

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**Author:** [@improbable22](https://discourse.julialang.org/u/improbable22)\
**Replies:** 2\
**Last updated:** [August 19, 2018, 9:56am UTC](https://discourse.julialang.org/t/logabsdet-singular/13706 "2018-08-19T09:56:57Z")

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I have lots of matrices with very small positive eigenvalues. In Julia 0.6 I was calling ld, s = logabsdet(m), but updating to v0.7, this now gives an error when det(m)==0. (It’s not physically zero, just numerical preci…

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## [Learning how to help with the Plots.jl effort?](https://discourse.julialang.org/t/learning-how-to-help-with-the-plots-jl-effort/13680)

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**Author:** [@djsegal](https://discourse.julialang.org/u/djsegal)\
**Replies:** 5\
**Last updated:** [August 19, 2018, 8:43am UTC](https://discourse.julialang.org/t/learning-how-to-help-with-the-plots-jl-effort/13680 "2018-08-19T08:43:52Z")

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I love Plots.jl, you love Plots.jl, everyone loves Plots.jl. The problem is making a flexible plotting framework is a huge task that’s probably not given the open-source effort it needs. Can we make a table that lists…

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## [Converting all NaN's to Missing and vice-versa in relevant columns](https://discourse.julialang.org/t/converting-all-nans-to-missing-and-vice-versa-in-relevant-columns/13675)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 2\
**Last updated:** [August 18, 2018, 9:39pm UTC](https://discourse.julialang.org/t/converting-all-nans-to-missing-and-vice-versa-in-relevant-columns/13675 "2018-08-18T21:39:47Z")

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I am experimenting with dataframes and missings, which have of course morphed over the last few months. my dataframes can have float columns that are already unions(missing), float columns that are not yet unions, and …

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## [Go-like select statement](https://discourse.julialang.org/t/go-like-select-statement/13684)

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**Author:** [@maurocchi](https://discourse.julialang.org/u/maurocchi)\
**Replies:** 0\
**Last updated:** [August 18, 2018, 9:35pm UTC](https://discourse.julialang.org/t/go-like-select-statement/13684 "2018-08-18T21:35:09Z")

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Is there in the Julia standard library something to mime the behaviour of the Golang select statement against the provided Channels?

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## [Way to add colorbar label to pgfplot in Plots.jl framework?](https://discourse.julialang.org/t/way-to-add-colorbar-label-to-pgfplot-in-plots-jl-framework/13655)

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**Author:** [@djsegal](https://discourse.julialang.org/u/djsegal)\
**Replies:** 1\
**Last updated:** [August 18, 2018, 10:12am UTC](https://discourse.julialang.org/t/way-to-add-colorbar-label-to-pgfplot-in-plots-jl-framework/13655 "2018-08-18T10:12:28Z")

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I have the following plot: The only thing really missing from it, though, is a label above the colorbar saying B\_0 How do you do this?

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## [IJulia + PyPlot: Error on plot()](https://discourse.julialang.org/t/ijulia-pyplot-error-on-plot/13436)

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**Author:** [@v-i-s-h](https://discourse.julialang.org/u/v-i-s-h)\
**Replies:** 1\
**Last updated:** [August 18, 2018, 8:30am UTC](https://discourse.julialang.org/t/ijulia-pyplot-error-on-plot/13436 "2018-08-18T08:30:21Z")

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Hi, I’m trying to use IJulia+PyPlot in Julia 1.0. From REPL, I’m able to plot. however if I use IJulia notebook and try plot( cumsum(rand(100)) ), the following error is coming. PyError ($(Expr(:escape, :(ccall(#= /…

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## [Flux v0.6.0: "MethodError: no method matching Flux.LSTMCell"](https://discourse.julialang.org/t/flux-v0-6-0-methoderror-no-method-matching-flux-lstmcell/13476)

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**Author:** [@Joshua\_Bowles](https://discourse.julialang.org/u/Joshua_Bowles)\
**Replies:** 1\
**Last updated:** [August 18, 2018, 3:13am UTC](https://discourse.julialang.org/t/flux-v0-6-0-methoderror-no-method-matching-flux-lstmcell/13476 "2018-08-18T03:13:08Z")

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Flux: Version 0.6.0 Julia: Version 0.7.0 Working through flux model zoo, lang-detection/model.jl:28, and trying to update to julia7. You can also reproduce the erorr by just Flux.LSTM(15,15) or Flux.LSTMCell(15, 15) f…

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## [A bit more information about "Integration of OpenCV and JuliaImages"](https://discourse.julialang.org/t/a-bit-more-information-about-integration-of-opencv-and-juliaimages/8824)

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**Author:** [@insoluble](https://discourse.julialang.org/u/insoluble)\
**Replies:** 3\
**Last updated:** [August 17, 2018, 10:36pm UTC](https://discourse.julialang.org/t/a-bit-more-information-about-integration-of-opencv-and-juliaimages/8824 "2018-08-17T22:36:47Z")

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Hi, I want to contribute to this project. I have fair understanding of C++ but new to openCV. Currently I am trying to understand this project. Apart from that on which area should I focus more and know about to be ab…

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## [A type for metadata?](https://discourse.julialang.org/t/a-type-for-metadata/10456)

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**Author:** [@kevbonham](https://discourse.julialang.org/u/kevbonham)\
**Replies:** 11\
**Last updated:** [August 17, 2018, 6:24pm UTC](https://discourse.julialang.org/t/a-type-for-metadata/10456 "2018-08-17T18:24:46Z")

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I’m routinely dealing with data + metadata, and I wanted to get some feedback on ideas for how to operationalize this. I’m a biologist, not a programmer, so it’s likely I’m overlooking some obvious solution. I’ll explain…

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## [Slow exp()?](https://discourse.julialang.org/t/slow-exp/13606)

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**Author:** [@tomtom](https://discourse.julialang.org/u/tomtom)\
**Replies:** 12\
**Last updated:** [August 17, 2018, 11:10am UTC](https://discourse.julialang.org/t/slow-exp/13606 "2018-08-17T11:10:44Z")

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julia\> exp(1.3) 3.6692966676192444 julia\> exp(1) 2.718281828459045 julia\> 2.718281828459045 ^ 1.3 3.669296667619244 julia\> @benchmark exp(1.3) BenchmarkTools.Trial: memory estimate: 0 bytes allocs estimate: 0 …

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## [How to properly plot DataFrames? (... and simplify my call to violin in StatPlots.)](https://discourse.julialang.org/t/how-to-properly-plot-dataframes-and-simplify-my-call-to-violin-in-statplots/13509)

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**Author:** [@rickhg12hs](https://discourse.julialang.org/u/rickhg12hs)\
**Replies:** 9\
**Last updated:** [August 17, 2018, 10:52am UTC](https://discourse.julialang.org/t/how-to-properly-plot-dataframes-and-simplify-my-call-to-violin-in-statplots/13509 "2018-08-17T10:52:48Z")

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I’m looking for a more concise way to call violin. I just want a violin of each category/column of data and also have all the labeling consistent with the Dataframe names. # some data to play with n = 10000 f(k) = rand…

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## [Resurrecting universal database API](https://discourse.julialang.org/t/resurrecting-universal-database-api/11412)

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**Author:** [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Replies:** 60\
**Last updated:** [August 17, 2018, 4:23am UTC](https://discourse.julialang.org/t/resurrecting-universal-database-api/11412 "2018-08-17T04:23:38Z")

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Based, on the other thread, it sounds like there is some interest in resurrecting the idea of a “universal Julia database API”. There are already some great Julia database packages, and thanks to ODBC.jl and JDBC.jl at …

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## [Error handling in JuMP](https://discourse.julialang.org/t/error-handling-in-jump/13584)

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**Author:** [@shoshievass](https://discourse.julialang.org/u/shoshievass)\
**Replies:** 2\
**Last updated:** [August 16, 2018, 8:58pm UTC](https://discourse.julialang.org/t/error-handling-in-jump/13584 "2018-08-16T20:58:03Z")

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I’m trying to use a JuMP model as an input to an ODE solver (using the DifferentialEquations.jl package). It seems to work well most of the time, but occasionally, the solver will output warnings at intermediate values a…

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