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diff --git a/chart2/source/tools/ExponentialRegressionCurveCalculator.cxx b/chart2/source/tools/ExponentialRegressionCurveCalculator.cxx
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+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed
+ * with this work for additional information regarding copyright
+ * ownership. The ASF licenses this file to you under the Apache
+ * License, Version 2.0 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of
+ * the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+#include <ExponentialRegressionCurveCalculator.hxx>
+#include <RegressionCalculationHelper.hxx>
+#include <SpecialCharacters.hxx>
+
+#include <rtl/math.hxx>
+#include <rtl/ustrbuf.hxx>
+
+using namespace ::com::sun::star;
+
+namespace chart
+{
+
+ExponentialRegressionCurveCalculator::ExponentialRegressionCurveCalculator()
+ : m_fLogSlope(0.0)
+ , m_fLogIntercept(0.0)
+ , m_fSign(1.0)
+{
+ ::rtl::math::setNan( & m_fLogSlope );
+ ::rtl::math::setNan( & m_fLogIntercept );
+}
+
+ExponentialRegressionCurveCalculator::~ExponentialRegressionCurveCalculator()
+{}
+
+// ____ XRegressionCurveCalculator ____
+void SAL_CALL ExponentialRegressionCurveCalculator::recalculateRegression(
+ const uno::Sequence< double >& aXValues,
+ const uno::Sequence< double >& aYValues )
+{
+ RegressionCalculationHelper::tDoubleVectorPair aValues(
+ RegressionCalculationHelper::cleanup(
+ aXValues, aYValues,
+ RegressionCalculationHelper::isValidAndYPositive()));
+ m_fSign = 1.0;
+
+ size_t nMax = aValues.first.size();
+ if( nMax <= 1 ) // at least 2 points
+ {
+ aValues = RegressionCalculationHelper::cleanup(
+ aXValues, aYValues,
+ RegressionCalculationHelper::isValidAndYNegative());
+ nMax = aValues.first.size();
+ if( nMax <= 1 )
+ {
+ ::rtl::math::setNan( & m_fLogSlope );
+ ::rtl::math::setNan( & m_fLogIntercept );
+ ::rtl::math::setNan( & m_fCorrelationCoefficient );// actual it is coefficient of determination
+ return;
+ }
+ m_fSign = -1.0;
+ }
+
+ double fAverageX = 0.0, fAverageY = 0.0;
+ double fLogIntercept = ( mForceIntercept && (m_fSign * mInterceptValue)>0 ) ? log(m_fSign * mInterceptValue) : 0.0;
+ std::vector<double> yVector;
+ yVector.resize(nMax, 0.0);
+
+ size_t i = 0;
+ for( i = 0; i < nMax; ++i )
+ {
+ double yValue = log( m_fSign *aValues.second[i] );
+ if (mForceIntercept)
+ {
+ yValue -= fLogIntercept;
+ }
+ else
+ {
+ fAverageX += aValues.first[i];
+ fAverageY += yValue;
+ }
+ yVector[i] = yValue;
+ }
+
+ const double fN = static_cast< double >( nMax );
+ fAverageX /= fN;
+ fAverageY /= fN;
+
+ double fQx = 0.0, fQy = 0.0, fQxy = 0.0;
+ for( i = 0; i < nMax; ++i )
+ {
+ double fDeltaX = aValues.first[i] - fAverageX;
+ double fDeltaY = yVector[i] - fAverageY;
+
+ fQx += fDeltaX * fDeltaX;
+ fQy += fDeltaY * fDeltaY;
+ fQxy += fDeltaX * fDeltaY;
+ }
+
+ m_fLogSlope = fQxy / fQx;
+ m_fLogIntercept = mForceIntercept ? fLogIntercept : fAverageY - m_fLogSlope * fAverageX;
+ m_fCorrelationCoefficient = fQxy / sqrt( fQx * fQy );
+}
+
+double SAL_CALL ExponentialRegressionCurveCalculator::getCurveValue( double x )
+{
+ double fResult;
+ ::rtl::math::setNan( & fResult );
+
+ if( ! ( std::isnan( m_fLogSlope ) ||
+ std::isnan( m_fLogIntercept )))
+ {
+ fResult = m_fSign * exp(m_fLogIntercept + x * m_fLogSlope);
+ }
+
+ return fResult;
+}
+
+uno::Sequence< geometry::RealPoint2D > SAL_CALL ExponentialRegressionCurveCalculator::getCurveValues(
+ double min, double max, ::sal_Int32 nPointCount,
+ const uno::Reference< chart2::XScaling >& xScalingX,
+ const uno::Reference< chart2::XScaling >& xScalingY,
+ sal_Bool bMaySkipPointsInCalculation )
+{
+ if( bMaySkipPointsInCalculation &&
+ isLinearScaling( xScalingX ) &&
+ isLogarithmicScaling( xScalingY ))
+ {
+ // optimize result
+ uno::Sequence< geometry::RealPoint2D > aResult( 2 );
+ aResult[0].X = min;
+ aResult[0].Y = getCurveValue( min );
+ aResult[1].X = max;
+ aResult[1].Y = getCurveValue( max );
+
+ return aResult;
+ }
+
+ return RegressionCurveCalculator::getCurveValues( min, max, nPointCount, xScalingX, xScalingY, bMaySkipPointsInCalculation );
+}
+
+OUString ExponentialRegressionCurveCalculator::ImplGetRepresentation(
+ const uno::Reference< util::XNumberFormatter >& xNumFormatter,
+ sal_Int32 nNumberFormatKey, sal_Int32* pFormulaMaxWidth /* = nullptr */ ) const
+{
+ double fIntercept = exp(m_fLogIntercept);
+ bool bHasSlope = !rtl::math::approxEqual( exp(m_fLogSlope), 1.0 );
+ bool bHasLogSlope = !rtl::math::approxEqual( fabs(m_fLogSlope), 1.0 );
+ bool bHasIntercept = !rtl::math::approxEqual( fIntercept, 1.0 ) && fIntercept != 0.0;
+
+ OUStringBuffer aBuf( mYName + " = " );
+ sal_Int32 nLineLength = aBuf.getLength();
+ sal_Int32 nValueLength=0;
+ if ( pFormulaMaxWidth && *pFormulaMaxWidth > 0 )
+ { // count characters different from coefficients
+ sal_Int32 nCharMin = nLineLength + 10 + mXName.getLength(); // 10 = "exp( ", " x )" + 2 extra characters
+ if ( m_fSign < 0.0 )
+ nCharMin += 2;
+ if ( fIntercept == 0.0 || ( !bHasSlope && m_fLogIntercept != 0.0 ) )
+ nCharMin += 3; // " + " special case where equation is written exp( a + b x )
+ if ( ( bHasIntercept || fIntercept == 0.0 || ( !bHasSlope && m_fLogIntercept != 0.0 ) ) &&
+ bHasLogSlope )
+ nValueLength = ( *pFormulaMaxWidth - nCharMin ) / 2;
+ else
+ nValueLength = *pFormulaMaxWidth - nCharMin;
+ if ( nValueLength <= 0 )
+ nValueLength = 1;
+ }
+ // temporary buffer
+ OUStringBuffer aTmpBuf("");
+ // if nValueLength not calculated then nullptr
+ sal_Int32* pValueLength = nValueLength ? &nValueLength : nullptr;
+ if ( m_fSign < 0.0 )
+ aTmpBuf.append( OUStringChar(aMinusSign) ).append( " " );
+ if ( bHasIntercept )
+ {
+ OUString aValueString = getFormattedString( xNumFormatter, nNumberFormatKey, fIntercept, pValueLength );
+ if ( aValueString != "1" ) // aValueString may be rounded to 1 if nValueLength is small
+ {
+ aTmpBuf.append( aValueString ).append( " " );
+ addStringToEquation( aBuf, nLineLength, aTmpBuf, pFormulaMaxWidth );
+ aTmpBuf.truncate();
+ }
+ }
+ aTmpBuf.append( "exp( " );
+ if ( !bHasIntercept )
+ {
+ if ( fIntercept == 0.0 || // underflow, a true zero is impossible
+ ( !bHasSlope && m_fLogIntercept != 0.0 ) ) // show logarithmic output, if intercept and slope both are near one
+ { // otherwise drop output of intercept, which is 1 here
+ OUString aValueString = getFormattedString( xNumFormatter, nNumberFormatKey, m_fLogIntercept, pValueLength );
+ if ( aValueString != "0" ) // aValueString may be rounded to 0 if nValueLength is small
+ {
+ aTmpBuf.append( aValueString ).append( (m_fLogSlope < 0.0) ? OUStringLiteral(" ") : OUStringLiteral(" + ") );
+ }
+ }
+ }
+ if ( m_fLogSlope < 0.0 )
+ aTmpBuf.append( OUStringChar(aMinusSign) ).append( " " );
+ if ( bHasLogSlope )
+ {
+ OUString aValueString = getFormattedString( xNumFormatter, nNumberFormatKey, fabs(m_fLogSlope), pValueLength );
+ if ( aValueString != "1" ) // aValueString may be rounded to 1 if nValueLength is small
+ {
+ aTmpBuf.append( aValueString ).append( " " );
+ }
+ }
+ aTmpBuf.append( mXName ).append(" )");
+ addStringToEquation( aBuf, nLineLength, aTmpBuf, pFormulaMaxWidth );
+
+ return aBuf.makeStringAndClear();
+}
+
+} // namespace chart
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */