Flute acoustics: measurement, modelling and design - School of ...

APPENDIX B. PROGRAM LISTINGS 259
}
}
if(ascent) {
seq_dec++;
seq_inc--;
}
}
}
return extv;
Extremum parabolaExt(Vector points, minmax type, int weight) {
Extremum ext = (Extremum)malloc(sizeof(*ext));
int numext;
double a, b, c, delta;
double x0, y0;
double minf;
double maxf;
/* compute least squares parabolic fit from data vector */
delta = det(D(points));
a = (1.0/delta)*det(A(points));
b = (1.0/delta)*det(B(points));
c = (1.0/delta)*det(C(points));
if(type == MINIMUM) {
ext->type = MINIMUM;
/* determine analytical minimum from parabola fit */
x0 = -1.0*(b/(2.0*c));
y0 = a + b*x0 + c*x0*x0;
if(weight) {
/* find frequency of absolute minimum in data vector */
minf = lowest(points);
numext = numExtrema(points, MINIMUM);
/* if only one minimum in set, heavily weight to absolute
minimum */
if(numext == 1) {
ext->f = (x0*minf)/(0.95*x0 + 0.05*minf);
}
/* otherwise, moderately weight towards absolute minimum */
else {
ext->f = (x0*minf)/(0.75*x0 + 0.25*minf);
}
}
/* if weight is false, use fit to determine f */
else
ext->f = x0;
/* construct minimum ...
impedance is parabola minimum
bandwidth and Q factor is 3dB span of parabola */
ext->Z = y0;
ext->B =