# MethodOfLines

**URL:** <https://discourse.julialang.org/t/methodoflines/108387>\
**Category:** General Usage\
**Tags:** question, package\
**Created:** [January 5, 2024, 12:55pm UTC](https://discourse.julialang.org/t/methodoflines/108387 "2024-01-05T12:55:12Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![Naceur\_Bouziani](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/naceur_bouziani/32/35768_2.png) [@Naceur\_Bouziani](https://discourse.julialang.org/u/Naceur_Bouziani)\
**Post date:** [January 5, 2024, 12:55pm UTC](https://discourse.julialang.org/t/methodoflines/108387/1 "2024-01-05T12:55:12Z")

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Hi Everybody & happy new year to all 🙂

Happy new year Alex and Chris 🙂

I installed the new version of Julia 1.10. I was surprised by not usual error in MethodOfLines package … so I uninstalled it and used the one proposed in this fork

> **[GitHub - AayushSabharwal/MethodOfLines.jl at as/issymbollike](https://github.com/AayushSabharwal/MethodOfLines.jl/tree/as/issymbollike)**
>
> as/issymbollike

but this did not work I still have the exact same error bellow

UndefVarError: `issymbollike` not defined

Stacktrace:  
[1] getindex(A::SciMLBase.PDETimeSeriesSolution{Float64, 2, Dict{Num, Array{Float64, 3}}, MethodOfLines.MOLMetadata{Val{true}(), MethodOfLines.DiscreteSpace{2, 2, MethodOfLines.CenterAlignedGrid}, MOLFiniteDifference{MethodOfLines.CenterAlignedGrid, MethodOfLines.ScalarizedDiscretization}, PDESystem, Base.RefValue{Any}, Nothing, MethodOfLines.ScalarizedDiscretization},

…

@ MethodOfLines ~/.julia/packages/MethodOfLines/qu7lv/src/interface/solution/common.jl:49

I will be happy if one of you folks could help me … maybe I’m not using the package proposed by **Aayush Sabharwal** the right way ?

What I did is : 1- remove the official MethodOfLines and 2- install the one proposed by **Aayush Sabharwal**

this way

] add [GitHub - AayushSabharwal/MethodOfLines.jl: Automatic Finite Difference PDE solving with Julia SciML](https://github.com/AayushSabharwal/MethodOfLines.jl.git)

I do not know If I’m doing this right ?

Naceur

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<div class="post-metadata">

**Author:** ![Naceur\_Bouziani](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/naceur_bouziani/32/35768_2.png) [@Naceur\_Bouziani](https://discourse.julialang.org/u/Naceur_Bouziani)\
**Post date:** [January 5, 2024, 5:12pm UTC](https://discourse.julialang.org/t/methodoflines/108387/2 "2024-01-05T17:12:27Z")

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Everything go fine until the need to retrieve the solution in order to plot it to analyze the physics. The bug seems to occur at that very last stage, that all what I can say for now.

Naceur

None of the examples provided in the doc page works now ☹ !  
They all worked just fine before.

The error is : **UndefVarError: `issymbollike` not defined**

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**Author:** ![gabo-di](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gabo-di/32/206427_2.png) [@gabo-di](https://discourse.julialang.org/u/gabo-di)\
**Post date:** [January 5, 2024, 8:24pm UTC](https://discourse.julialang.org/t/methodoflines/108387/3 "2024-01-05T20:24:43Z")

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Hi, first of all you can use an Environment for this Project. Here you install all that you need and when installing Method of Lines you use `add https://github.com/AayushSabharwal/MethodOfLines.jl#as/issymbollike` i.e. “”“add [https://github.com/username/package\_name#branch\_name](https://github.com/username/package_name#branch_name)”“” then it will work nicely

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**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [January 6, 2024, 12:56am UTC](https://discourse.julialang.org/t/methodoflines/108387/4 "2024-01-06T00:56:24Z")

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> <https://github.com/SciML/MethodOfLines.jl/pull/346>
>
> \## Checklist
> 
> \- \[\] Appropriate tests were added
> \- \[\] Any code changes were …done in a way that does not break public API
> \- \[\] All documentation related to code changes were updated
> \- \[\] The new code follows the
> \[contributor guidelines\](https://github.com/SciML/.github/blob/master/CONTRIBUTING.md), in particular the \[SciML Style Guide\](https://github.com/SciML/SciMLStyle) and
> \[COLPRAC\](https://github.com/SciML/COLPRAC).
> \- \[\] Any new documentation only uses public API
>   
> \## Additional context
> 
> Add any other context about the problem here.

MethodOfLines didn’t quite follow the symbolic indexing interface and so when it updated it didn’t have a kind effect on it 😅. We’re working through this.

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<div class="post-metadata">

**Author:** ![Naceur\_Bouziani](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/naceur_bouziani/32/35768_2.png) [@Naceur\_Bouziani](https://discourse.julialang.org/u/Naceur_Bouziani)\
**Post date:** [January 6, 2024, 9:11am UTC](https://discourse.julialang.org/t/methodoflines/108387/5 "2024-01-06T09:11:49Z")

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Hi Gabo 🙂

I did that, create a directory in which I installed all the needed packages along with the proposed fork of MethodOfLines as I mentioned

It seems that colleagues are working hard to solve the issue.

Have a nice day  
Naceur

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<div class="post-metadata">

**Author:** ![Naceur\_Bouziani](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/naceur_bouziani/32/35768_2.png) [@Naceur\_Bouziani](https://discourse.julialang.org/u/Naceur_Bouziani)\
**Post date:** [January 6, 2024, 9:34am UTC](https://discourse.julialang.org/t/methodoflines/108387/6 "2024-01-06T09:34:10Z")

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Hi Chris 🙂

Great ! I will wait until the tests give you the green light. 🙂

If something changes in our syntax to retrieve the solution,  
for example, a new way of writing the following :

```julia
discrete_x = sol[x]
discrete_y = sol[y]
discrete_t = sol[t]

solu = sol[u(x, y, t)]
solv = sol[v(x, y, t)]

```

In The Brusselator PDE web page example. I will be happy to write this in all the web pages of the tutorials, if this could save you some time, that’s easy for me it’s just syntax and tests of all the provided examples 😃

Have A Nice Day

Naceur

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**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [January 6, 2024, 3:34pm UTC](https://discourse.julialang.org/t/methodoflines/108387/7 "2024-01-06T15:34:36Z")

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I don’t think we plan to change that surface level syntax, just how it’s done.

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<div class="post-metadata">

**Author:** ![Naceur\_Bouziani](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/naceur_bouziani/32/35768_2.png) [@Naceur\_Bouziani](https://discourse.julialang.org/u/Naceur_Bouziani)\
**Post date:** [January 7, 2024, 2:42pm UTC](https://discourse.julialang.org/t/methodoflines/108387/8 "2024-01-07T14:42:23Z")

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Yes, Chris, Right 🙂 And this makes a lot of sense if the surface level is invariant. This is always the case with Julia’s updates, packages get better and better without asking the user to change the syntax

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**Author:** ![gdmcbain](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gdmcbain/32/205280_2.png) [@gdmcbain](https://discourse.julialang.org/u/gdmcbain)\
**Post date:** [January 19, 2024, 5:58am UTC](https://discourse.julialang.org/t/methodoflines/108387/9 "2024-01-19T05:58:30Z")

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Hi there. Working through the [MethodOfLines tutorial](https://docs.sciml.ai/MethodOfLines/stable/tutorials/brusselator/) myself just now in Julia 1.10, I hit the same trouble [extracting results](https://docs.sciml.ai/MethodOfLines/stable/tutorials/brusselator/#Extracting-results) and a WWW-search for the `UndefVarError` led me here. By poking around in `sol` in the VS Code IDE, I did find a way to reproduce the GIF:

```julia
anim = @animate for (k, tk) in enumerate(sol.t)
    heatmap(sol.u[v(x, y, t)][2:end, 2:end, k], title="$tk")
end

```

We don’t need the coordinates for this, but they can be obtained with, e.g., `sol.disc_data.discretespace.grid[x]`.