CMSSW Reference Manual

List of all members.


Public Member Functions
float	intercept (const vector< float > &x, const vector< float > &y, int ndat, const vector< float > &sigx, const vector< float > &sigy) const
	Approached intercept computed with approached slope.
float	slope (const vector< float > &x, const vector< float > &y, int ndat, const vector< float > &sigx, const vector< float > &sigy) const
	Approached slope: rescale y and sigy by var(x)/var(y) fit a straight line with weights derived from the scaled sum sigx^2 + sigy^2.
Private Member Functions
float	variance (const vector< float > &x, int ndat) const

Detailed Description

Member Function Documentation

float LinearFitErrorsIn2Coord::intercept	(	const vector< float > &	x,
		const vector< float > &	y,
		int	ndat,
		const vector< float > &	sigx,
		const vector< float > &	sigy
	)			const

Approached intercept computed with approached slope.

Definition at line 33 of file LinearFitErrorsIn2Coord.cc.

References i, and slope().

00036 {
00037   
00038   float fs = slope(x, y, ndat, sigx, sigy);
00039   float fi = 0;
00040   float sumWi = 0;
00041   for (int i = 0; i != ndat; i++) {
00042     float wi = 1./(sigy[i] + fs*fs*sigx[i]);
00043     fi += wi*(y[i] - fs*x[i]);
00044     sumWi += wi;
00045   }
00046 
00047   return fi / sumWi;
00048 
00049 }

float LinearFitErrorsIn2Coord::slope	(	const vector< float > &	x,
		const vector< float > &	y,
		int	ndat,
		const vector< float > &	sigx,
		const vector< float > &	sigy
	)			const

Approached slope:

rescale y and sigy by var(x)/var(y)
fit a straight line with weights derived from the scaled sum sigx^2 + sigy^2.

Definition at line 5 of file LinearFitErrorsIn2Coord.cc.

References LinearFit::fit(), i, scale, funct::sqrt(), and variance().

Referenced by intercept().

00008 {
00009 
00010   // scale y and sigy, compute scaled errors
00011   float scale = sqrt(variance(x, ndat) / variance(y, ndat));
00012   vector<float> yScaled = y;
00013   vector<float> sigyScaled = sigy;
00014   vector<float> sig(ndat);
00015   for (int i = 0; i != ndat; i++) {
00016     yScaled[i] *= scale; 
00017     sigyScaled[i] *= scale;
00018     sig[i] = sqrt(sigx[i]*sigx[i] + sigyScaled[i]*sigyScaled[i]);
00019   }
00020 
00021   // usual linear fit
00022   LinearFit lf;
00023   float fs, fi, covss, covii, covsi;
00024   lf.fit(x, yScaled, ndat, sig, fs, fi, covss, covii, covsi);
00025 
00026   // unscale result
00027   fs /= scale;
00028   return fs;
00029 
00030 }

float LinearFitErrorsIn2Coord::variance	(	const vector< float > &	x,
		int	ndat
	)			const `[private]`

Definition at line 53 of file LinearFitErrorsIn2Coord.cc.

References i, and m1.

Referenced by slope().

00054 {
00055   double m1 = 0., m2 = 0.;
00056   for (int i = 0; i != ndat; i++) {
00057     m1 += x[i];
00058     m2 += x[i]*x[i];
00059   }
00060   m1 /= ndat;
00061   m2 /= ndat;
00062 
00063   return float(m2 - m1*m1);
00064 
00065 }

LinearFitErrorsIn2Coord Class Reference

Public Member Functions

Private Member Functions

Detailed Description

Member Function Documentation