82 lines
2.9 KiB
C++
82 lines
2.9 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/*
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* This file is part of the LibreOffice project.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* This file incorporates work covered by the following license notice:
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed
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* with this work for additional information regarding copyright
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* ownership. The ASF licenses this file to you under the Apache
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* License, Version 2.0 (the "License"); you may not use this file
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* except in compliance with the License. You may obtain a copy of
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* the License at http://www.apache.org/licenses/LICENSE-2.0 .
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*/
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#pragma once
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#include "global.hxx"
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class SubTotal
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{
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public:
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static bool SafePlus( double& fVal1, double fVal2);
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static bool SafeMult( double& fVal1, double fVal2);
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static bool SafeDiv( double& fVal1, double fVal2);
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};
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class ScFunctionData;
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/** Implements the Welford Online one-pass algorithm.
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See https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_Online_algorithm
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and Donald E. Knuth, TAoCP vol.2, 3rd edn., p. 232
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*/
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class WelfordRunner
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{
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public:
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WelfordRunner() : mfMean(0.0), mfM2(0.0), mnCount(0) {}
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void update( double fVal );
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sal_uInt64 getCount() const { return mnCount; }
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double getVarianceSample() const { return mnCount > 1 ? mfM2 / (mnCount-1) : 0.0; }
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double getVariancePopulation() const { return mnCount > 0 ? mfM2 / mnCount : 0.0; }
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// The private variables can be abused by ScFunctionData as general
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// sum/min/max/ave/count/... variables to reduce memory footprint for that
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// ScFunctionData may be a mass object during consolidation.
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// ScFunctionData::update() and getResult() take care that purposes are not
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// mixed.
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friend class ScFunctionData;
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private:
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double mfMean;
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double mfM2;
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sal_uInt64 mnCount;
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};
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/** To calculate a single subtotal function. */
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class ScFunctionData
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{
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public:
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ScFunctionData() : meFunc(SUBTOTAL_FUNC_NONE), mbError(false) {}
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ScFunctionData( ScSubTotalFunc eFn ) : meFunc(eFn), mbError(false) {}
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void update( double fNewVal );
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/// Check getError() after (!) obtaining the result.
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double getResult();
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bool getError() const { return mbError; }
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ScSubTotalFunc getFunc() const { return meFunc; }
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void setError() { mbError = true; }
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private:
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WelfordRunner maWelford;
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ScSubTotalFunc meFunc;
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bool mbError;
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double& getValueRef() { return maWelford.mfMean; }
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sal_uInt64& getCountRef() { return maWelford.mnCount; }
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};
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/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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