I am using DifferentialEquations.jl in a Julia Notebook. The code starts as:

```
using DifferentalEquations
using ParameterizedFunctions
sir_ode = @ode_def SIRModel begin
dS = -β*S*I
dI = β*S*I-γ*I
dR = γ*I
end β γ
```

When executed, I get the error:

```
UndefVarError: @ode_def not defined
```

That does not seem possible. What can I do about it? Thanks.

1 Like

That doesn’t seem possible. uhh, what versions?

You are correct, it does not seem possible. Here is a status list of precompiled binaries in Julia 1.4.

```
Status `~/.julia/environments/v1.4/Project.toml`
[c52e3926] Atom v0.12.11
[fbb218c0] BSON v0.2.6
[aae01518] BandedMatrices v0.15.7
[6e4b80f9] BenchmarkTools v0.5.0
[0487d830] Bifurcations v0.0.1 #master (https://github.com/tkf/Bifurcations.jl.git)
[2b5f629d] DiffEqBase v6.35.1
[aae7a2af] DiffEqFlux v1.10.3
[9fdde737] DiffEqOperators v4.10.0
[0c46a032] DifferentialEquations v6.14.0
[bbc10e6e] DynamicHMC v2.1.0
[5789e2e9] FileIO v1.3.0
[587475ba] Flux v0.10.4
[7073ff75] IJulia v1.21.2
[82e4d734] ImageIO v0.1.1
[916415d5] Images v0.22.2
[18b7da76] JuliaAcademyData v0.1.0 #master (https://github.com/JuliaComputing/JuliaAcademyData.jl)
[e5e0dc1b] Juno v0.8.2
[ee78f7c6] Makie v0.10.0
[429524aa] Optim v0.21.0
[65888b18] ParameterizedFunctions v5.3.0
[d96e819e] Parameters v0.12.1
[91a5bcdd] Plots v0.29.9
[92933f4c] ProgressMeter v1.3.0
[7186c646] PyDSTool v0.6.0
[d330b81b] PyPlot v2.9.0
[295af30f] Revise v2.6.7
[efcf1570] Setfield v0.6.0
[90137ffa] StaticArrays v0.12.3
[37b6cedf] Traceur v0.3.1
[37e2e46d] LinearAlgebra
```

I just typed into my notebook (did the same in Atom):

```
MethodError: no method matching @ode_def(::LineNumberNode, ::Module)
Closest candidates are:
@ode_def(::LineNumberNode, ::Module, !Matched::Any, !Matched::Any, !Matched::Any...) at /Users/erlebach/.julia/packages/ParameterizedFunctions/xErQf/src/macros.jl:2
```

which suggests that @ode_def was found. So I will try to use it again. But I am sure that what I reported happened.

I exited Jupyter and started it up again. The problem went away. As usual: “rebooting” solves many issues. Not elegant though.

Did your packages update mid-notebook? If you do that, you need a new Julia session to use the newer versions, so it could be something like that?

1 Like

Hi, I get the same error which doesn’t disappear though. I tried Jupyter, Vscode, Pluto.

It says UndefVarError. Any more help on this? I do not have problem with other functions though.

Did you do `using ParameterizedFunctions`

?

1 Like

Hi Chris, yes, exactly. I am watching your video on YouTube on DifferentialEquations.jl. First really thanks for the package, huge work, really really appreciate it. But in your video because I follow your notebook and I did not see using ParameterizedFunctions (maybe I did not notice it) I got the problem. anyway thanks again for responding and for the excellent work.

Note that ode_def was deprecated in 2020, and thus one needs to do `using ParameterizedFunctions`

(and add that package) in order to use that functionality. This is already the reason why you will no longer find it in the DifferentialEquations.jl documentation. I added a comment to the video to hopefully help the next person who might run into this. Yeah, videos can’t easily be updated , but it’s still almost all still relevant.

1 Like

Yeah, I see. actually there are some other changes (like there is no more A_mul_B! function and instead we have mul! which is part of LinearAlgebra, or A + B + C works exactly like A .+ B .+ C and … ) but as you said it is hard to update videos and these all can be searched.

thanks Chris again for the help