How to solve two-order differential equation using ode23

like this equation.this equation is a complex matrix,some of my codes is :

    function dydt=mytest1(t,x)
    exp1=inv(M)*f;
    dydt=[x(4);x(5);x(6);exp1];

I use the ode23 function to sover it.,but I get this error:

    Error using odearguments (line 111)
    Inputs must be floats, namely single or double.

    Error in ode23 (line 113)
    [neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...

Answer 1

[zhang]

I know how to sove it ,however thanks