QgsHistogram Class Reference

Calculator for a numeric histogram from a list of values. More...

#include <qgshistogram.h>

Public Member Functions
	QgsHistogram ()=default
	Constructor for QgsHistogram. More...
virtual	~QgsHistogram ()=default
QList< double >	binEdges (int bins) const
	Returns a list of edges for the histogram for a specified number of bins. More...
QList< int >	counts (int bins) const
	Returns the calculated list of the counts for the histogram bins. More...
double	optimalBinWidth () const
	Calculates the optimal bin width using the Freedman-Diaconis rule. More...
int	optimalNumberBins () const
	Returns the optimal number of bins for the source values, calculated using the Freedman-Diaconis rule. More...
void	setValues (const QList< double > &values)
	Assigns numeric source values for the histogram. More...
bool	setValues (const QgsVectorLayer *layer, const QString &fieldOrExpression, QgsFeedback *feedback=nullptr)
	Assigns numeric source values for the histogram from a vector layer's field or as the result of an expression. More...

Detailed Description

Calculator for a numeric histogram from a list of values.

Since

QGIS 2.9

Definition at line 37 of file qgshistogram.h.

Constructor & Destructor Documentation

QgsHistogram::QgsHistogram ( )

default

Constructor for QgsHistogram.

virtual QgsHistogram::~QgsHistogram ( )

virtualdefault

Member Function Documentation

QList< double > QgsHistogram::binEdges

(

int

bins

)

const

Returns a list of edges for the histogram for a specified number of bins.

This list will be length bins + 1, as both the first and last value are also included.

Parameters

bins	number of bins

Returns

list of bin edges

Note

values must first be specified using setValues()

Definition at line 68 of file qgshistogram.cpp.

QList< int > QgsHistogram::counts

(

int

bins

)

const

Returns the calculated list of the counts for the histogram bins.

Parameters

bins	number of histogram bins

Returns

list of histogram counts

Note

values must first be specified using setValues()

Definition at line 84 of file qgshistogram.cpp.

double QgsHistogram::optimalBinWidth

(

)

const

Calculates the optimal bin width using the Freedman-Diaconis rule.

Bins widths are determined by the inter-quartile range of values and the number of values.

Returns

optimal width for bins

See also

optimalNumberBins

Note

values must first be specified using setValues()

Definition at line 57 of file qgshistogram.cpp.

int QgsHistogram::optimalNumberBins

(

)

const

Returns the optimal number of bins for the source values, calculated using the Freedman-Diaconis rule.

The number of bins are determined by the inter-quartile range of values and the number of values.

Returns

optimal number of bins

See also

optimalBinWidth

Note

values must first be specified using setValues()

Definition at line 63 of file qgshistogram.cpp.

void QgsHistogram::setValues

(

const QList< double > &

values

)

Assigns numeric source values for the histogram.

Parameters

values

list of doubles

Definition at line 36 of file qgshistogram.cpp.

bool QgsHistogram::setValues	(	const QgsVectorLayer *	layer,
		const QString &	fieldOrExpression,
		QgsFeedback *	feedback = nullptr
	)

Assigns numeric source values for the histogram from a vector layer's field or as the result of an expression.

Parameters

layer	vector layer
fieldOrExpression	field name or expression to be evaluated
feedback	optional feedback object to allow cancellation of calculation

Returns

true if values were successfully set

Definition at line 42 of file qgshistogram.cpp.

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The documentation for this class was generated from the following files:

• /build/qgis-3.4.15+24xenial/src/core/qgshistogram.h
• /build/qgis-3.4.15+24xenial/src/core/qgshistogram.cpp