extern double	uniformrand(double, double);
extern double	normalrand(double, double);
extern double	nrand(void);
extern double	exponetialrand(double);

extern void	differential(int, double *, double *, double);
extern void	lowpass(int, double *, double *, double, double, double);

static char	*samplingtimeformat = "#sampling time = %lf\n";
static char	*numdataformat      = "#number of data = %d\n";