Index: scaddins/source/analysis/analysishelper.cxx
===================================================================
RCS file: /cvs/sc/scaddins/source/analysis/analysishelper.cxx,v
retrieving revision 1.48
diff -u -r1.48 analysishelper.cxx
--- scaddins/source/analysis/analysishelper.cxx	8 Sep 2005 23:20:16 -0000	1.48
+++ scaddins/source/analysis/analysishelper.cxx	7 Oct 2005 02:53:21 -0000
@@ -838,14 +838,18 @@
 
 	return aRet;
 }
-
-
-double Erf( double x )
+/** Calculates erf(x) by using Maclaurin expansion.  Accurate up to
+	x = 4.
+ */
+void ErfMaclaurin( double x, double& fErf )
 {
 	if( x == 0.0 )
-		return 0.0;
+	{
+		fErf = 0.0;
+		return;
+	}
 
-	double		f, fZm, fN2, fn1, fOld, fT;
+	double		fZm, fN2, fn1, fOld, fT;
 	sal_Bool	bAdd = sal_True;
 	sal_Int32	nMaxIter = 1000;
 
@@ -857,13 +861,13 @@
 
 	fT = x * fZm;
 
-	f = x - fT / fN2;
+	fErf = x - fT / fN2;
 
-	fOld = f * 0.9;
+	fOld = fErf * 0.9;
 
-	while( f != fOld && nMaxIter )
+	while( fErf != fOld && nMaxIter-- )
 	{
-		fOld = f;
+		fOld = fErf;
 
 		fN2 += 2.0;
 
@@ -873,18 +877,96 @@
 		fn1++;
 
 		if( bAdd )
-			f += fT / fN2;
+			fErf += fT / fN2;
 		else
-			f -= fT / fN2;
+			fErf -= fT / fN2;
 
 		bAdd = !bAdd;
+	}
+
+	fErf *= 1.1283791670955125738961589031215452;
+}
+
+/** Calculates erf(x) by using Asymptotic expansion.  Accurate for x > 4
+	but converges more quickly than octave/gnumeric.  Calculated values
+	are almost identical to Excel's.
+
+	@author Kohei Yoshida <kohei@openoffice.org>
+
+	@see #i19991#
+ */
+void ErfAsymptotic( double x, double& fErf )
+{
+	if( x == 0.0 )
+	{
+		fErf = 0.0;
+		return;
+	}
+
+	long nMaxIter = 1000;
+
+	double fFct2 = 1.0, fDenom = 1.0, fX = x, fn = 0.0;
+	double fXCnt = 1.0;
+	double f = 1.0 / fX;
+	double fOld = f * 0.9;
 
-		nMaxIter--;
+	bool bAdd = false;
+	double fDiff = 0.0, fDiffOld = 1000.0;
+	while( f != fOld && nMaxIter-- )
+	{
+		fOld = f;
+
+		fFct2 *= 2.0*++fn - 1.0;
+		fDenom *= 2.0;
+		fX *= x*x;
+		fXCnt += 2.0;
+
+		if ( bAdd )
+			f += fFct2 / ( fDenom * fX );
+		else
+			f -= fFct2 / ( fDenom * fX );
+
+		bAdd = !bAdd;
+		
+		fDiff = fabs( f - fOld );
+		if ( fDiffOld < fDiff )
+		{
+			f = fOld;
+			break;
+		}
+		fDiffOld = fDiff;
 	}
 
-	return f * 1.128379167095512573896;	// * 2/sqrt(PI)
+	fErf = 1.0 - f*exp( -1.0*x*x )*0.5641895835477562869480794515607726;
 }
 
+/** Parent erf function that calls two different algorithms based on value
+	of x.  It takes care of cases where x is negative ( erf is an odd function
+	i.e. f(-x) = -f(x) ).
+
+	@author Kohei Yoshida <kohei@openoffice.org>
+
+	@see #i19991#
+ */
+double Erf( double x )
+{
+	bool bNegative = false;
+	if ( x < 0.0 )
+	{
+		x = fabs( x );
+		bNegative = true;
+	}
+	
+	double fErf;
+	if ( x > 4.0 )
+		ErfAsymptotic( x, fErf );
+	else
+		ErfMaclaurin( x, fErf );
+
+	if ( bNegative )
+		fErf *= -1.0;
+	return fErf;
+}
 
 inline sal_Bool IsNum( sal_Unicode c )
 {