Method Error when using solve in DifferentialEquations.jl

General Usage
,
1

I’m working through the first example in the Ordinary Differential Equations section of DifferentialEquations.jl documentation, and when I call solve(prob,Tsit5(),reltol=1e-8,abstol=1e-8), I get

MethodError: no method matching f(::Float64, ::DiffEqBase.NullParameters, ::Float64)

I’ve tried uninstalling and reinstalling.

My package status reads:

C:\Users\jmurp.julia\environments\v1.5\Project.toml`
[c52e3926] Atom v0.12.19
[2b5f629d] DiffEqBase v6.45.0
[0c46a032] DifferentialEquations v6.15.0
[e5e0dc1b] Juno v0.8.3
[1dea7af3] OrdinaryDiffEq v5.42.3
[91a5bcdd] Plots v1.6.0

Any help would be appreciated.

2

What does your definition of f look like?

(Side note: If you put your code in a block surrounded by triple back-ticks it will be easier to read.)

3

Here is my code.

using DifferentialEquations
using Plots

f(t,u) = 1.01*u
u0 = .5
tspan = (0.0, 1.0)

prob = ODEProblem(f, u0, tspan)
sol = solve(prob,Tsit5(),reltol=1e-8,abstol=1e-8)
4

The function should be:

f(u,p,t) = 1.01*u
5

I think at one point, the function signature looked like f(t,u), similar to the MATLAB convention, but it has since changed to f(u,p,t) (or f(du,u,p,t) for the in-place version). If you’re looking at documentation that still has f(t,u), it’s out of date.

6

That fixed it, thank you.

It looks like it was old documentation, must have clicked on some old link somewhere.

Thanks again

1 Like
7

Yeah… I think that was 2017. How was the old link found? I think Google is the only thing that still digs up those old docs.

8

It was from google, when I searched “Julia Diffeq Uncertainty” it was the first link.