Calculate the moments of a histogram

moment.C

//usr/bin/env root -l -b -q "$0( $1, \"$2\" )"; exit $?


/* Calculate the nth moment of a distribution
 *
 * int n : order of the moment to calculate
 * TString filehist : 
 */
double moment( int n = 1, TString filehist = "", float x1=0, float x2=-1 ){
	cout << "Calculating moment " << n << " on " << filehist << endl;
	

	TObjArray *tx = filehist.Tokenize(":");
	if ( tx->GetEntries() < 2 ){
		cout << "Usage : " << endl;
		cout << "./moment.C <n> <filehist>" << endl;
		cout << "\tn : order of moment to calculate" << endl;
		cout << "\tfilehist : should specify the filename and the hist name separated by a \":\" e.g. \"tfile.root:hsimple\" " << endl;
		exit(0);
	}
	TString fname = ((TObjString*)tx->At(0))->GetString();
	TString hname = ((TObjString*)tx->At(1))->GetString();

	TFile * f = new TFile( fname );
	TH1 * h = (TH1 * )f->Get( hname );
	h->Scale( 1.0 / h->Integral("width") );

	// get the bounds (currently only if used as function in root prompt)
	bool boundsCheck = false;
	if ( x2 > x1 ) {// not defaults
		boundsCheck = true;
		cout << "Calculating moment in " << x1 << " to " << x2  << endl;
		h->Scale( 1.0 / h->Integral( h->FindBin(x1), h->FindBin(x2), "width") );
	}

	float m = 0;
	for ( int i = 1; i < h->GetNbinsX() + 1; i++ ){
		float x = h->GetBinCenter( i );
		float dx = h->GetBinWidth( i );
		
		if ( boundsCheck && ( x-dx/2. < x1 || x+dx/2.0 > x2 ) )
			continue;

		float y = h->GetBinContent( i );

		float _x = pow( x, n );

		m += _x * dx * y;
	}


	return m;
}

the bounds checking may be causing a small error. Need to check how to handle normalization integral vs. bound checks