sfduffing1 (2.0-git)
1D signal analysis by using Duffing differential equation solved by 4th order Runge-Kutta method.

        sfduffing1 < in.rsf > out.rsf restor=restor.rsf gamma=0.75 omega=1 kxi=1 x0=0 y0=0 pow1=1 pow2=3 phi=0. verb=n cosine=y
Duffing equation: x''/(omega^2)+0.5 x'/omega-x+x^3=gamma cos(omega t+phi)+kxi R(t)

bool cosine=y [y/n]
if n need extenal input for periodic restoring force
float gamma=0.75
strength of external force
float kxi=1
adjustment for input signal
float omega=1
angular frequence of external force
float phi=0.
phase of cosine signal unit=pi
int pow1=1
power of first non-linear restitution term
int pow2=3
power of second non-linear restitution term
string restor=
auxiliary input file name
bool verb=n [y/n]
verbosity flag
float x0=0
initial value of x0
float y0=0
initial value of y0