QGIS API Documentation 3.30.0-'s-Hertogenbosch (f186b8efe0)
qgsalgorithmnearestneighbouranalysis.cpp
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1/***************************************************************************
2 qgsalgorithmnearestneighbouranalysis.cpp
3 ---------------------
4 begin : December 2019
5 copyright : (C) 2019 by Alexander Bruy
6 email : alexander dot bruy 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
19#include "qgsapplication.h"
20#include "qgsdistancearea.h"
21#include <QTextStream>
22
24
25QString QgsNearestNeighbourAnalysisAlgorithm::name() const
26{
27 return QStringLiteral( "nearestneighbouranalysis" );
28}
29
30QString QgsNearestNeighbourAnalysisAlgorithm::displayName() const
31{
32 return QObject::tr( "Nearest neighbour analysis" );
33}
34
35QStringList QgsNearestNeighbourAnalysisAlgorithm::tags() const
36{
37 return QObject::tr( "point,node,vertex,nearest,neighbour,distance" ).split( ',' );
38}
39
40QString QgsNearestNeighbourAnalysisAlgorithm::group() const
41{
42 return QObject::tr( "Vector analysis" );
43}
44
45QString QgsNearestNeighbourAnalysisAlgorithm::groupId() const
46{
47 return QStringLiteral( "vectoranalysis" );
48}
49
50QString QgsNearestNeighbourAnalysisAlgorithm::shortHelpString() const
51{
52 return QObject::tr( "This algorithm performs nearest neighbor analysis for a point layer.\n\n"
53 "The output describes how the data are distributed (clustered, randomly or distributed).\n\n"
54 "Output is generated as an HTML file with the computed statistical values." );
55}
56
57QString QgsNearestNeighbourAnalysisAlgorithm::svgIconPath() const
58{
59 return QgsApplication::iconPath( QStringLiteral( "/algorithms/mAlgorithmNearestNeighbour.svg" ) );
60}
61
62QIcon QgsNearestNeighbourAnalysisAlgorithm::icon() const
63{
64 return QgsApplication::getThemeIcon( QStringLiteral( "/algorithms/mAlgorithmNearestNeighbour.svg" ) );
65}
66
67QgsNearestNeighbourAnalysisAlgorithm *QgsNearestNeighbourAnalysisAlgorithm::createInstance() const
68{
69 return new QgsNearestNeighbourAnalysisAlgorithm();
70}
71
72void QgsNearestNeighbourAnalysisAlgorithm::initAlgorithm( const QVariantMap & )
73{
74 addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ), QObject::tr( "Input layer" ), QList< int >() << QgsProcessing::TypeVectorPoint ) );
75 addParameter( new QgsProcessingParameterFileDestination( QStringLiteral( "OUTPUT_HTML_FILE" ), QObject::tr( "Nearest neighbour" ),
76 QObject::tr( "HTML files (*.html *.HTML)" ), QVariant(), true ) );
77 addOutput( new QgsProcessingOutputNumber( QStringLiteral( "OBSERVED_MD" ), QObject::tr( "Observed mean distance" ) ) );
78 addOutput( new QgsProcessingOutputNumber( QStringLiteral( "EXPECTED_MD" ), QObject::tr( "Expected mean distance" ) ) );
79 addOutput( new QgsProcessingOutputNumber( QStringLiteral( "NN_INDEX" ), QObject::tr( "Nearest neighbour index" ) ) );
80 addOutput( new QgsProcessingOutputNumber( QStringLiteral( "POINT_COUNT" ), QObject::tr( "Number of points" ) ) );
81 addOutput( new QgsProcessingOutputNumber( QStringLiteral( "Z_SCORE" ), QObject::tr( "Z-score" ) ) );
82}
83
84QVariantMap QgsNearestNeighbourAnalysisAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
85{
86 std::unique_ptr< QgsProcessingFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
87 if ( !source )
88 throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
89
90 const QString outputFile = parameterAsFileOutput( parameters, QStringLiteral( "OUTPUT_HTML_FILE" ), context );
91
92 const QgsSpatialIndex spatialIndex( *source, feedback, QgsSpatialIndex::FlagStoreFeatureGeometries );
94 da.setSourceCrs( source->sourceCrs(), context.transformContext() );
95 da.setEllipsoid( context.ellipsoid() );
96
97 const double step = source->featureCount() ? 100.0 / source->featureCount() : 1;
98 QgsFeatureIterator it = source->getFeatures( QgsFeatureRequest().setSubsetOfAttributes( QList< int >() ) );
99
100 const QgsFeatureRequest request;
101 const QgsFeature neighbour;
102 double sumDist = 0.0;
103 const double area = source->sourceExtent().width() * source->sourceExtent().height();
104
105 int i = 0;
106 QgsFeature f;
107 while ( it.nextFeature( f ) )
108 {
109 if ( feedback->isCanceled() )
110 {
111 break;
112 }
113
114 const QgsFeatureId neighbourId = spatialIndex.nearestNeighbor( f.geometry().asPoint(), 2 ).at( 1 );
115 sumDist += da.measureLine( spatialIndex.geometry( neighbourId ).asPoint(), f.geometry().asPoint() );
116
117 i++;
118 feedback->setProgress( i * step );
119 }
120
121 const long long count = source->featureCount() > 0 ? source->featureCount() : 1;
122 const double observedDistance = sumDist / count;
123 const double expectedDistance = 0.5 / std::sqrt( count / area );
124 const double nnIndex = observedDistance / expectedDistance;
125 const double se = 0.26136 / std::sqrt( std::pow( count, 2 ) / area );
126 const double zScore = ( observedDistance - expectedDistance ) / se;
127
128 QVariantMap outputs;
129 outputs.insert( QStringLiteral( "OBSERVED_MD" ), observedDistance );
130 outputs.insert( QStringLiteral( "EXPECTED_MD" ), expectedDistance );
131 outputs.insert( QStringLiteral( "NN_INDEX" ), nnIndex );
132 outputs.insert( QStringLiteral( "POINT_COUNT" ), count );
133 outputs.insert( QStringLiteral( "Z_SCORE" ), zScore );
134
135 if ( !outputFile.isEmpty() )
136 {
137 QFile file( outputFile );
138 if ( file.open( QIODevice::WriteOnly | QIODevice::Truncate ) )
139 {
140 QTextStream out( &file );
141#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
142 out.setCodec( "UTF-8" );
143#endif
144 out << QStringLiteral( "<html><head><meta http-equiv=\"Content-Type\" content=\"text/html;charset=utf-8\"/></head><body>\n" );
145 out << QObject::tr( "<p>Observed mean distance: %1</p>\n" ).arg( observedDistance, 0, 'f', 11 );
146 out << QObject::tr( "<p>Expected mean distance: %1</p>\n" ).arg( expectedDistance, 0, 'f', 11 );
147 out << QObject::tr( "<p>Nearest neighbour index: %1</p>\n" ).arg( nnIndex, 0, 'f', 11 );
148 out << QObject::tr( "<p>Number of points: %1</p>\n" ).arg( count );
149 out << QObject::tr( "<p>Z-Score: %1</p>\n" ).arg( zScore, 0, 'f', 11 );
150 out << QStringLiteral( "</body></html>" );
151
152 outputs.insert( QStringLiteral( "OUTPUT_HTML_FILE" ), outputFile );
153 }
154 }
155
156 return outputs;
157}
158
static QIcon getThemeIcon(const QString &name, const QColor &fillColor=QColor(), const QColor &strokeColor=QColor())
Helper to get a theme icon.
static QString iconPath(const QString &iconFile)
Returns path to the desired icon file.
A general purpose distance and area calculator, capable of performing ellipsoid based calculations.
double measureLine(const QVector< QgsPointXY > &points) const
Measures the length of a line with multiple segments.
void setSourceCrs(const QgsCoordinateReferenceSystem &crs, const QgsCoordinateTransformContext &context)
Sets source spatial reference system crs.
bool setEllipsoid(const QString &ellipsoid)
Sets the ellipsoid by its acronym.
Wrapper for iterator of features from vector data provider or vector layer.
bool nextFeature(QgsFeature &f)
This class wraps a request for features to a vector layer (or directly its vector data provider).
The feature class encapsulates a single feature including its unique ID, geometry and a list of field...
Definition: qgsfeature.h:56
QgsGeometry geometry
Definition: qgsfeature.h:67
bool isCanceled() const SIP_HOLDGIL
Tells whether the operation has been canceled already.
Definition: qgsfeedback.h:54
void setProgress(double progress)
Sets the current progress for the feedback object.
Definition: qgsfeedback.h:63
QgsPointXY asPoint() const
Returns the contents of the geometry as a 2-dimensional point.
Contains information about the context in which a processing algorithm is executed.
QgsCoordinateTransformContext transformContext() const
Returns the coordinate transform context.
QString ellipsoid() const
Returns the ellipsoid to use for distance and area calculations.
Custom exception class for processing related exceptions.
Definition: qgsexception.h:83
Base class for providing feedback from a processing algorithm.
A numeric output for processing algorithms.
An input feature source (such as vector layers) parameter for processing algorithms.
A generic file based destination parameter, for specifying the destination path for a file (non-map l...
@ TypeVectorPoint
Vector point layers.
Definition: qgsprocessing.h:50
A spatial index for QgsFeature objects.
@ FlagStoreFeatureGeometries
Indicates that the spatial index should also store feature geometries. This requires more memory,...
qint64 QgsFeatureId
64 bit feature ids negative numbers are used for uncommitted/newly added features
Definition: qgsfeatureid.h:28