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diff --git a/chart2/source/tools/PotentialRegressionCurveCalculator.cxx b/chart2/source/tools/PotentialRegressionCurveCalculator.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 <PotentialRegressionCurveCalculator.hxx>
+#include <RegressionCalculationHelper.hxx>
+#include <SpecialCharacters.hxx>
+
+#include <limits>
+#include <rtl/math.hxx>
+#include <rtl/ustrbuf.hxx>
+
+using namespace ::com::sun::star;
+
+namespace chart
+{
+
+PotentialRegressionCurveCalculator::PotentialRegressionCurveCalculator()
+ : m_fSlope(std::numeric_limits<double>::quiet_NaN())
+ , m_fIntercept(std::numeric_limits<double>::quiet_NaN())
+ , m_fSign(1.0)
+{
+}
+
+PotentialRegressionCurveCalculator::~PotentialRegressionCurveCalculator()
+{}
+
+// ____ XRegressionCurveCalculator ____
+void SAL_CALL PotentialRegressionCurveCalculator::recalculateRegression(
+ const uno::Sequence< double >& aXValues,
+ const uno::Sequence< double >& aYValues )
+{
+ RegressionCalculationHelper::tDoubleVectorPair aValues(
+ RegressionCalculationHelper::cleanup(
+ aXValues, aYValues,
+ RegressionCalculationHelper::isValidAndBothPositive()));
+ m_fSign = 1.0;
+
+ size_t nMax = aValues.first.size();
+ if( nMax <= 1 ) // at least 2 points
+ {
+ aValues = RegressionCalculationHelper::cleanup(
+ aXValues, aYValues,
+ RegressionCalculationHelper::isValidAndXPositiveAndYNegative());
+ nMax = aValues.first.size();
+ if( nMax <= 1 )
+ {
+ m_fSlope = std::numeric_limits<double>::quiet_NaN();
+ m_fIntercept = std::numeric_limits<double>::quiet_NaN();
+ m_fCorrelationCoefficient = std::numeric_limits<double>::quiet_NaN();
+ return;
+ }
+ m_fSign = -1.0;
+ }
+
+ double fAverageX = 0.0, fAverageY = 0.0;
+ size_t i = 0;
+ for( i = 0; i < nMax; ++i )
+ {
+ fAverageX += log( aValues.first[i] );
+ fAverageY += log( m_fSign * aValues.second[i] );
+ }
+
+ 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 = log( aValues.first[i] ) - fAverageX;
+ double fDeltaY = log( m_fSign * aValues.second[i] ) - fAverageY;
+
+ fQx += fDeltaX * fDeltaX;
+ fQy += fDeltaY * fDeltaY;
+ fQxy += fDeltaX * fDeltaY;
+ }
+
+ m_fSlope = fQxy / fQx;
+ m_fIntercept = fAverageY - m_fSlope * fAverageX;
+ m_fCorrelationCoefficient = fQxy / sqrt( fQx * fQy );
+
+ m_fIntercept = m_fSign * exp( m_fIntercept );
+}
+
+double SAL_CALL PotentialRegressionCurveCalculator::getCurveValue( double x )
+{
+ if( ! ( std::isnan( m_fSlope ) ||
+ std::isnan( m_fIntercept )))
+ {
+ return m_fIntercept * pow( x, m_fSlope );
+ }
+
+ return std::numeric_limits<double>::quiet_NaN();
+}
+
+uno::Sequence< geometry::RealPoint2D > SAL_CALL PotentialRegressionCurveCalculator::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 &&
+ isLogarithmicScaling( xScalingX ) &&
+ isLogarithmicScaling( xScalingY ))
+ {
+ // optimize result
+ uno::Sequence< geometry::RealPoint2D > aResult{ { min, getCurveValue( min ) },
+ { max, getCurveValue( max ) } };
+
+ return aResult;
+ }
+ return RegressionCurveCalculator::getCurveValues( min, max, nPointCount, xScalingX, xScalingY, bMaySkipPointsInCalculation );
+}
+
+OUString PotentialRegressionCurveCalculator::ImplGetRepresentation(
+ const uno::Reference< util::XNumberFormatter >& xNumFormatter,
+ sal_Int32 nNumberFormatKey, sal_Int32* pFormulaMaxWidth /* = nullptr */ ) const
+{
+ bool bHasIntercept = !rtl::math::approxEqual( fabs(m_fIntercept), 1.0 );
+ OUStringBuffer aBuf( mYName + " = " );
+ sal_Int32 nLineLength = aBuf.getLength();
+ sal_Int32 nValueLength=0;
+ if ( pFormulaMaxWidth && *pFormulaMaxWidth > 0 ) // count nValueLength
+ {
+ sal_Int32 nCharMin = nLineLength + mXName.getLength() + 3; // 3 = "^" + 2 extra characters
+ if ( m_fIntercept != 0.0 && m_fSlope != 0.0 )
+ {
+ if ( m_fIntercept < 0.0 )
+ nCharMin += 2; // "- "
+ if ( bHasIntercept )
+ nValueLength = (*pFormulaMaxWidth - nCharMin) / 2;
+ }
+ if ( nValueLength == 0 ) // not yet calculated
+ nValueLength = *pFormulaMaxWidth - nCharMin;
+ if ( nValueLength <= 0 )
+ nValueLength = 1;
+ }
+
+ if( m_fIntercept == 0.0 )
+ {
+ aBuf.append( '0' );
+ }
+ else
+ {
+ // temporary buffer
+ OUStringBuffer aTmpBuf("");
+ // if nValueLength not calculated then nullptr
+ sal_Int32* pValueLength = nValueLength ? &nValueLength : nullptr;
+ if ( m_fIntercept < 0.0 ) // add intercept value
+ aTmpBuf.append( OUStringChar(aMinusSign) + " " );
+ if( bHasIntercept )
+ {
+ OUString aValueString = getFormattedString( xNumFormatter, nNumberFormatKey, fabs(m_fIntercept), pValueLength );
+ if ( aValueString != "1" ) // aValueString may be rounded to 1 if nValueLength is small
+ {
+ aTmpBuf.append( aValueString + " " );
+ }
+ }
+ if( m_fSlope != 0.0 ) // add slope value
+ {
+ aTmpBuf.append( mXName + "^" );
+ aTmpBuf.append( getFormattedString( xNumFormatter, nNumberFormatKey, m_fSlope, pValueLength ));
+ }
+ addStringToEquation( aBuf, nLineLength, aTmpBuf, pFormulaMaxWidth );
+ }
+
+ return aBuf.makeStringAndClear();
+}
+
+} // namespace chart
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */