QGIS API Documentation  3.25.0-Master (10b47c2603)
qgshistogram.cpp
Go to the documentation of this file.
1 /***************************************************************************
2  qgshistogram.cpp
3  ----------------
4  begin : May 2015
5  copyright : (C) 2015 by Nyall Dawson
6  email : nyall dot dawson at gmail dot com
7  ***************************************************************************/
8 
9 /***************************************************************************
10  * *
11  * This program is free software; you can redistribute it and/or modify *
12  * it under the terms of the GNU General Public License as published by *
13  * the Free Software Foundation; either version 2 of the License, or *
14  * (at your option) any later version. *
15  * *
16  ***************************************************************************/
17 
18 #include "qgshistogram.h"
19 
20 #include "qgsstatisticalsummary.h"
21 #include "qgsvectorlayer.h"
22 #include "qgsvectorlayerutils.h"
23 
24 void QgsHistogram::prepareValues()
25 {
26  std::sort( mValues.begin(), mValues.end() );
27 
30  s.calculate( mValues );
31  mMin = s.min();
32  mMax = s.max();
33  mIQR = s.interQuartileRange();
34 }
35 
36 void QgsHistogram::setValues( const QList<double> &values )
37 {
38  mValues = values;
39  prepareValues();
40 }
41 
42 bool QgsHistogram::setValues( const QgsVectorLayer *layer, const QString &fieldOrExpression, QgsFeedback *feedback )
43 {
44  mValues.clear();
45  if ( !layer )
46  return false;
47 
48  bool ok;
49  mValues = QgsVectorLayerUtils::getDoubleValues( layer, fieldOrExpression, ok, false, nullptr, feedback );
50  if ( !ok )
51  return false;
52 
53  prepareValues();
54  return true;
55 }
56 
58 {
59  //Freedman-Diaconis rule
60  return 2.0 * mIQR * std::pow( mValues.count(), -1 / 3.0 );
61 }
62 
64 {
65  return std::ceil( ( mMax - mMin ) / optimalBinWidth() );
66 }
67 
68 QList<double> QgsHistogram::binEdges( int bins ) const
69 {
70  const double binWidth = ( mMax - mMin ) / bins;
71 
72  QList<double> edges;
73  edges.reserve( bins + 1 );
74  edges << mMin;
75  double current = mMin;
76  for ( int i = 0; i < bins; ++i )
77  {
78  current += binWidth;
79  edges << current;
80  }
81  return edges;
82 }
83 
84 QList<int> QgsHistogram::counts( int bins ) const
85 {
86  const QList<double> edges = binEdges( bins );
87 
88  QList<int> binCounts;
89  binCounts.reserve( bins );
90  int currentValueIndex = 0;
91  for ( int i = 0; i < bins; ++i )
92  {
93  int count = 0;
94  while ( currentValueIndex < mValues.count() && mValues.at( currentValueIndex ) < edges.at( i + 1 ) )
95  {
96  count++;
97  currentValueIndex++;
98  if ( currentValueIndex >= mValues.count() )
99  break;
100  }
101  binCounts << count;
102  }
103 
104  if ( currentValueIndex < mValues.count() )
105  {
106  //last value needs to be added
107  binCounts[ bins - 1 ] = binCounts.last() + 1;
108  }
109 
110  return binCounts;
111 }
112 
113 
Base class for feedback objects to be used for cancellation of something running in a worker thread.
Definition: qgsfeedback.h:45
QList< int > counts(int bins) const
Returns the calculated list of the counts for the histogram bins.
int optimalNumberBins() const
Returns the optimal number of bins for the source values, calculated using the Freedman-Diaconis rule...
double optimalBinWidth() const
Calculates the optimal bin width using the Freedman-Diaconis rule.
QList< double > binEdges(int bins) const
Returns a list of edges for the histogram for a specified number of bins.
void setValues(const QList< double > &values)
Assigns numeric source values for the histogram.
Calculator for summary statistics for a list of doubles.
void calculate(const QList< double > &values)
Calculates summary statistics for a list of values.
@ InterQuartileRange
Inter quartile range (IQR)
double interQuartileRange() const
Returns the inter quartile range of the values.
double min() const
Returns calculated minimum from values.
void setStatistics(QgsStatisticalSummary::Statistics stats)
Sets flags which specify which statistics will be calculated.
double max() const
Returns calculated maximum from values.
static QList< double > getDoubleValues(const QgsVectorLayer *layer, const QString &fieldOrExpression, bool &ok, bool selectedOnly=false, int *nullCount=nullptr, QgsFeedback *feedback=nullptr)
Fetches all double values from a specified field name or expression.
Represents a vector layer which manages a vector based data sets.