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112 lines
3.6 KiB
C++
112 lines
3.6 KiB
C++
/***************************************************************************
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qgshistogram.h
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--------------
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begin : May 2015
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copyright : (C) 2015 by Nyall Dawson
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email : nyall dot dawson at gmail dot com
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***************************************************************************/
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/***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************/
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#ifndef QGSHISTOGRAM_H
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#define QGSHISTOGRAM_H
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#include <QList>
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#include "qgis_core.h"
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#include "qgsfeedback.h"
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class QgsVectorLayer;
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/**
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* \ingroup core
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* \class QgsHistogram
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* \brief Calculator for a numeric histogram from a list of values.
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*
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* \since QGIS 2.9
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*/
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class CORE_EXPORT QgsHistogram
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{
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public:
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/**
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* Constructor for QgsHistogram.
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*/
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QgsHistogram() = default;
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virtual ~QgsHistogram() = default;
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/**
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* Assigns numeric source values for the histogram.
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* \param values list of doubles
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*/
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void setValues( const QList<double> &values );
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/**
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* Assigns numeric source values for the histogram from a vector layer's field or as the
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* result of an expression.
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* \param layer vector layer
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* \param fieldOrExpression field name or expression to be evaluated
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* \param feedback optional feedback object to allow cancelation of calculation
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* \returns true if values were successfully set
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*/
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bool setValues( const QgsVectorLayer *layer, const QString &fieldOrExpression, QgsFeedback *feedback = nullptr );
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/**
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* Calculates the optimal bin width using the Freedman-Diaconis rule. Bins widths are
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* determined by the inter-quartile range of values and the number of values.
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* \returns optimal width for bins
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* \see optimalNumberBins
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* \note values must first be specified using setValues()
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*/
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double optimalBinWidth() const;
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/**
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* Returns the optimal number of bins for the source values, calculated using the
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* Freedman-Diaconis rule. The number of bins are determined by the inter-quartile range
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* of values and the number of values.
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* \returns optimal number of bins
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* \see optimalBinWidth
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* \note values must first be specified using setValues()
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*/
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int optimalNumberBins() const;
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/**
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* Returns a list of edges for the histogram for a specified number of bins. This list
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* will be length bins + 1, as both the first and last value are also included.
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* \param bins number of bins
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* \returns list of bin edges
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* \note values must first be specified using setValues()
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*/
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QList<double> binEdges( int bins ) const;
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/**
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* Returns the calculated list of the counts for the histogram bins.
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* \param bins number of histogram bins
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* \returns list of histogram counts
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* \note values must first be specified using setValues()
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*/
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QList<int> counts( int bins ) const;
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private:
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QList<double> mValues;
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double mMax = 0;
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double mMin = 0;
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double mIQR = 0;
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void prepareValues();
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};
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#endif // QGSHISTOGRAM_H
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