FFT from a time signal with unequal time increment

Hi everyone, I am trying to take a FFT from a simulated time signal, which is resulted from an ODE simulation. The problem is the unequal time steps by ODE and I don't know how should I make this FFT analysis in this case. Concerning the T as the time vector and Y as a simulated time signal, can anybody tell me how should I perform the FFT analysis? Many thanks in advance!

Answer 1

[Star Strider]

I would go back and re-run the ODE with a fixed time step, then use that to calculate the FFT.

Instead of giving the ODE solver a ‘tspan’ vector of a beginning and end time, such as:

tspan = [t_start  t_end];

give it a constant-step vector instead:

tspan = linspace(t_start, t_end, 50);

to create (for example) a 50-element equal-step time vector. The ODE solver will report the solutions very close to the time steps you specify.