JuliaLang/julia — Issue #365: some ode45 features
Author: JeffBezanson
Created: 2012-02-15 00:46:29+00:00
State: open
Labels: features, up for grabs

`ode45` should support stepping from high to low like `ode23` does, and both should also support any-size vectors of steps instead of just `[t0, tfinal]`.

I'd like to do

```
function tracywidom()
t0 = 5.
tn = -8.
dx = .005

deq = function (t::Float64, y::Vector{Float64})
[y[2]; t*y[1]+2*y[1]^3; y[4]; y[1]^2]
end

y0 = [airy(t0); airy(1,t0); 0; airy(t0)^2]

(t, y) = ode45(deq, [t0:-dx:tn], y0)

F2 = exp(-y[:,3][:])
f2 = gradient(F2,t)
return (t, f2)
end
```