void Ltas_fitTiltLine (Ltas me, double fmin, double fmax, bool lnf, int method, double *a, double *b) {
try {
if (fmax <= fmin) {
fmin = my xmin; fmax = my xmax;
}
long ifmin, ifmax, numberOfSamples = Sampled_getWindowSamples (me, fmin, fmax, &ifmin, &ifmax);
if (numberOfSamples < 2) {
Melder_throw ("There must be at least two data points to fit a line.");
}
autoNUMvector<double> x (1, numberOfSamples);
autoNUMvector<double> y (1, numberOfSamples);
for (long i = ifmin; i <= ifmax; i++) {
long ixy = i - ifmin + 1;
x[ixy] = my x1 + (i - 1) * my dx;
if (lnf) {
// For Ltas always x1 > 0
x[ixy] = log10 (x[ixy]);
}
y[ixy] = my z[1][i];
}
NUMlineFit (x.peek(), y.peek(), numberOfSamples, a, b, method);
} catch (MelderError) {
Melder_throw ("Tilt line not determined.");
}
}
/* Fit line y = ax+b (lineType ==1) or y = a log(x) + b (lineType == 2) on interval [qmin,qmax]
* method == 1 : Least squares fit
* method == 2 : Theil's partial robust fit
*/
void PowerCepstrum_fitTiltLine (PowerCepstrum me, double qmin, double qmax, double *p_a, double *p_intercept, int lineType, int method) {
try {
double a, intercept;
if (qmax <= qmin) {
qmin = my xmin; qmax = my xmax;
}
long imin, imax;
if (! Matrix_getWindowSamplesX (me, qmin, qmax, & imin, & imax)) {
return;
}
imin = (lineType == 2 && imin == 1) ? 2 : imin; // log(0) is undefined!
long numberOfPoints = imax - imin + 1;
if (numberOfPoints < 2) {
Melder_throw (U"Not enough points for fit.");
}
autoNUMvector<double> y (1, numberOfPoints);
autoNUMvector<double> x (1, numberOfPoints);
for (long i = 1; i <= numberOfPoints; i++) {
long isamp = imin + i - 1;
x[i] = my x1 + (isamp - 1) * my dx;
if (lineType == 2) {
x[i] = log (x[i]);
}
y[i] = my v_getValueAtSample (isamp, 1, 0);
}
if (method == 3) { // try local maxima first
autoNUMvector<double> ym (1, numberOfPoints / 2 + 1);
autoNUMvector<double> xm (1, numberOfPoints / 2 + 1);
long numberOfLocalPeaks = 0;
// forget y[1] if y[2]<y[1] and y[n] if y[n-1]<y[n] !
for (long i = 2; i <= numberOfPoints; i++) {
if (y[i - 1] <= y[i] && y[i] > y[i + 1]) {
ym[++numberOfLocalPeaks] = y[i];
xm[numberOfLocalPeaks] = x[i];
}
}
if (numberOfLocalPeaks > numberOfPoints / 10) {
for (long i = 1; i <= numberOfLocalPeaks; i++) {
x[i] = xm[i]; y[i] = ym[i];
}
numberOfPoints = numberOfLocalPeaks;
}
method = 2; // robust fit of peaks
}
// fit a straight line through (x,y)'s
NUMlineFit (x.peek(), y.peek(), numberOfPoints, & a, & intercept, method);
if (p_intercept) { *p_intercept = intercept; }
if (p_a) { *p_a = a; }
} catch (MelderError) {
Melder_throw (me, U": couldn't fit a line.");
}
}
