//===============================================================================
Double_t langaufungaus(Double_t *x, Double_t *par) {
return langaufun(x,par)+par[4]*TMath::Gaus(x[0],par[5],par[6],true);
};
Int_t langaupro(Double_t *params, Double_t &maxx, Double_t &FWHM) {
// Seaches for the location (x value) at the maximum of the
// Landau-Gaussian convolute and its full width at half-maximum.
//
// The search is probably not very efficient, but it's a first try.
Double_t p,x,fy,fxr,fxl;
Double_t step;
Double_t l,lold;
Int_t i = 0;
Int_t MAXCALLS = 10000;
// Search for maximum
p = params[1] - 0.1 * params[0];
step = 0.05 * params[0];
lold = -2.0;
l = -1.0;
while ( (l != lold) && (i < MAXCALLS) ) {
i++;
lold = l;
x = p + step;
l = langaufun(&x,params);
if (l < lold)
step = -step/10;
p += step;
}
if (i == MAXCALLS)
return (-1);
maxx = x;
fy = l/2;
// Search for right x location of fy
p = maxx + params[0];
step = params[0];
lold = -2.0;
l = -1e300;
i = 0;
while ( (l != lold) && (i < MAXCALLS) ) {
i++;
lold = l;
x = p + step;
l = TMath::Abs(langaufun(&x,params) - fy);
if (l > lold)
step = -step/10;
p += step;
}
if (i == MAXCALLS)
return (-2);
fxr = x;
// Search for left x location of fy
p = maxx - 0.5 * params[0];
step = -params[0];
lold = -2.0;
l = -1e300;
i = 0;
while ( (l != lold) && (i < MAXCALLS) ) {
i++;
lold = l;
x = p + step;
l = TMath::Abs(langaufun(&x,params) - fy);
if (l > lold)
step = -step/10;
p += step;
}
if (i == MAXCALLS)
return (-3);
fxl = x;
FWHM = fxr - fxl;
return (0);
}
