Class: QgsHistogram

class qgis.core.QgsHistogram

Bases: sip.wrapper

Calculator for a numeric histogram from a list of values.

New in version 2.9.

QgsHistogram() Constructor for QgsHistogram.

QgsHistogram(QgsHistogram)

Methods

binEdges

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

counts

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

optimalBinWidth

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

optimalNumberBins

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

setValues

Assigns numeric source values for the histogram.

binEdges(self, bins: int)List[float]

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 (int) – number of bins

Return type

List[float]

Returns

list of bin edges

Note

values must first be specified using setValues()

counts(self, bins: int)List[int]

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

Parameters

bins (int) – number of histogram bins

Return type

List[int]

Returns

list of histogram counts

Note

values must first be specified using setValues()

optimalBinWidth(self)float

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.

Return type

float

Returns

optimal width for bins

Note

values must first be specified using setValues()

optimalNumberBins(self)int

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.

Return type

int

Returns

optimal number of bins

Note

values must first be specified using setValues()

setValues(self, values: Iterable[float])

Assigns numeric source values for the histogram.

Parameters

values (Iterable[float]) – list of doubles

setValues(self, layer: QgsVectorLayer, fieldOrExpression: str, feedback: QgsFeedback = None) -> bool 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