How to include a filtered signal in ODE 45 solver

Hey, I am trying a solve a set of coupled differential equations. I am supposed to analyze the problem for various modulating input, which in itself is not that difficult at all. I would just simply include a sin(t) function wherever appropriate to that. I went on to do the same thing by replacing my input with a square wave. The ODE45 solver seems to be really bad at the sudden jumps, so I wish to input a filtered version, or a smoothed version of square wave as the input. I dont understand how to include that in the function handle, since any filter in matlab acts on a time series and I do not a time series unless I solve the differential equation. Any help/ suggestions along this line would be very helpful.

[Arjun Iyer]

I was thinking something simple like a bessel filtered square wave as the input.

Answer 1

[Naty S]

Just a thought but you could smooth how ever you like prior to the ODE and create a lookup table to replace the square function with the smoothed wave, you could probably approximate the square function with a different function as well again prior to the ODE.