Branch data     Line data    Source code

       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                 :            : 
      18                 :            : #include "qgsalgorithmnearestneighbouranalysis.h"
      19                 :            : #include "qgsapplication.h"
      20                 :            : #include <QTextStream>
      21                 :            : 
      22                 :            : ///@cond PRIVATE
      23                 :            : 
      24                 :          0 : QString QgsNearestNeighbourAnalysisAlgorithm::name() const
      25                 :            : {
      26                 :          0 :   return QStringLiteral( "nearestneighbouranalysis" );
      27                 :            : }
      28                 :            : 
      29                 :          0 : QString QgsNearestNeighbourAnalysisAlgorithm::displayName() const
      30                 :            : {
      31                 :          0 :   return QObject::tr( "Nearest neighbour analysis" );
      32                 :            : }
      33                 :            : 
      34                 :          0 : QStringList QgsNearestNeighbourAnalysisAlgorithm::tags() const
      35                 :            : {
      36                 :          0 :   return QObject::tr( "point,node,vertex,nearest,neighbour,distance" ).split( ',' );
      37                 :          0 : }
      38                 :            : 
      39                 :          0 : QString QgsNearestNeighbourAnalysisAlgorithm::group() const
      40                 :            : {
      41                 :          0 :   return QObject::tr( "Vector analysis" );
      42                 :            : }
      43                 :            : 
      44                 :          0 : QString QgsNearestNeighbourAnalysisAlgorithm::groupId() const
      45                 :            : {
      46                 :          0 :   return QStringLiteral( "vectoranalysis" );
      47                 :            : }
      48                 :            : 
      49                 :          0 : QString QgsNearestNeighbourAnalysisAlgorithm::shortHelpString() const
      50                 :            : {
      51                 :          0 :   return QObject::tr( "This algorithm performs nearest neighbor analysis for a point layer.\n\n"
      52                 :            :                       "The output describes how the data are distributed (clustered, randomly or distributed).\n\n"
      53                 :            :                       "Output is generated as an HTML file with the computed statistical values." );
      54                 :            : }
      55                 :            : 
      56                 :          0 : QString QgsNearestNeighbourAnalysisAlgorithm::svgIconPath() const
      57                 :            : {
      58                 :          0 :   return QgsApplication::iconPath( QStringLiteral( "/algorithms/mAlgorithmNearestNeighbour.svg" ) );
      59                 :          0 : }
      60                 :            : 
      61                 :          0 : QIcon QgsNearestNeighbourAnalysisAlgorithm::icon() const
      62                 :            : {
      63                 :          0 :   return QgsApplication::getThemeIcon( QStringLiteral( "/algorithms/mAlgorithmNearestNeighbour.svg" ) );
      64                 :          0 : }
      65                 :            : 
      66                 :          0 : QgsNearestNeighbourAnalysisAlgorithm *QgsNearestNeighbourAnalysisAlgorithm::createInstance() const
      67                 :            : {
      68                 :          0 :   return new QgsNearestNeighbourAnalysisAlgorithm();
      69                 :            : }
      70                 :            : 
      71                 :          0 : void QgsNearestNeighbourAnalysisAlgorithm::initAlgorithm( const QVariantMap & )
      72                 :            : {
      73                 :          0 :   addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ), QObject::tr( "Input layer" ), QList< int >() << QgsProcessing::TypeVectorPoint ) );
      74                 :          0 :   addParameter( new QgsProcessingParameterFileDestination( QStringLiteral( "OUTPUT_HTML_FILE" ), QObject::tr( "Nearest neighbour" ),
      75                 :          0 :                 QObject::tr( "HTML files (*.html *.HTML)" ), QVariant(), true ) );
      76                 :          0 :   addOutput( new QgsProcessingOutputNumber( QStringLiteral( "OBSERVED_MD" ), QObject::tr( "Observed mean distance" ) ) );
      77                 :          0 :   addOutput( new QgsProcessingOutputNumber( QStringLiteral( "EXPECTED_MD" ), QObject::tr( "Expected mean distance" ) ) );
      78                 :          0 :   addOutput( new QgsProcessingOutputNumber( QStringLiteral( "NN_INDEX" ), QObject::tr( "Nearest neighbour index" ) ) );
      79                 :          0 :   addOutput( new QgsProcessingOutputNumber( QStringLiteral( "POINT_COUNT" ), QObject::tr( "Number of points" ) ) );
      80                 :          0 :   addOutput( new QgsProcessingOutputNumber( QStringLiteral( "Z_SCORE" ), QObject::tr( "Z-score" ) ) );
      81                 :          0 : }
      82                 :            : 
      83                 :          0 : QVariantMap QgsNearestNeighbourAnalysisAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
      84                 :            : {
      85                 :          0 :   std::unique_ptr< QgsProcessingFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
      86                 :          0 :   if ( !source )
      87                 :          0 :     throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
      88                 :            : 
      89                 :          0 :   QString outputFile = parameterAsFileOutput( parameters, QStringLiteral( "OUTPUT_HTML_FILE" ), context );
      90                 :            : 
      91                 :          0 :   QgsSpatialIndex spatialIndex( *source, feedback, QgsSpatialIndex::FlagStoreFeatureGeometries );
      92                 :          0 :   QgsDistanceArea da;
      93                 :          0 :   da.setSourceCrs( source->sourceCrs(), context.transformContext() );
      94                 :          0 :   da.setEllipsoid( context.ellipsoid() );
      95                 :            : 
      96                 :          0 :   double step = source->featureCount() ? 100.0 / source->featureCount() : 1;
      97                 :          0 :   QgsFeatureIterator it = source->getFeatures( QgsFeatureRequest().setSubsetOfAttributes( QList< int >() ) );
      98                 :            : 
      99                 :          0 :   QgsFeatureRequest request;
     100                 :          0 :   QgsFeature neighbour;
     101                 :          0 :   double sumDist = 0.0;
     102                 :          0 :   double area = source->sourceExtent().width() * source->sourceExtent().height();
     103                 :            : 
     104                 :          0 :   int i = 0;
     105                 :          0 :   QgsFeature f;
     106                 :          0 :   while ( it.nextFeature( f ) )
     107                 :            :   {
     108                 :          0 :     if ( feedback->isCanceled() )
     109                 :            :     {
     110                 :          0 :       break;
     111                 :            :     }
     112                 :            : 
     113                 :          0 :     QgsFeatureId neighbourId = spatialIndex.nearestNeighbor( f.geometry().asPoint(), 2 ).at( 1 );
     114                 :          0 :     sumDist += da.measureLine( spatialIndex.geometry( neighbourId ).asPoint(), f.geometry().asPoint() );
     115                 :            : 
     116                 :          0 :     i++;
     117                 :          0 :     feedback->setProgress( i * step );
     118                 :            :   }
     119                 :            : 
     120                 :          0 :   int count = source->featureCount() > 0 ? source->featureCount() : 1;
     121                 :          0 :   double observedDistance = sumDist / count;
     122                 :          0 :   double expectedDistance = 0.5 / std::sqrt( count / area );
     123                 :          0 :   double nnIndex = observedDistance / expectedDistance;
     124                 :          0 :   double se = 0.26136 / std::sqrt( std::pow( count, 2 ) / area );
     125                 :          0 :   double zScore = ( observedDistance - expectedDistance ) / se;
     126                 :            : 
     127                 :          0 :   QVariantMap outputs;
     128                 :          0 :   outputs.insert( QStringLiteral( "OBSERVED_MD" ), observedDistance );
     129                 :          0 :   outputs.insert( QStringLiteral( "EXPECTED_MD" ), expectedDistance );
     130                 :          0 :   outputs.insert( QStringLiteral( "NN_INDEX" ), nnIndex );
     131                 :          0 :   outputs.insert( QStringLiteral( "POINT_COUNT" ), count );
     132                 :          0 :   outputs.insert( QStringLiteral( "Z_SCORE" ), zScore );
     133                 :            : 
     134                 :          0 :   if ( !outputFile.isEmpty() )
     135                 :            :   {
     136                 :          0 :     QFile file( outputFile );
     137                 :          0 :     if ( file.open( QIODevice::WriteOnly | QIODevice::Text ) )
     138                 :            :     {
     139                 :          0 :       QTextStream out( &file );
     140                 :          0 :       out << QStringLiteral( "<html><head><meta http-equiv=\"Content-Type\" content=\"text/html;charset=utf-8\"/></head><body>\n" );
     141                 :          0 :       out << QObject::tr( "<p>Observed mean distance: %1</p>\n" ).arg( observedDistance, 0, 'f', 11 );
     142                 :          0 :       out << QObject::tr( "<p>Expected mean distance: %1</p>\n" ).arg( expectedDistance, 0, 'f', 11 );
     143                 :          0 :       out << QObject::tr( "<p>Nearest neighbour index: %1</p>\n" ).arg( nnIndex, 0, 'f', 11 );
     144                 :          0 :       out << QObject::tr( "<p>Number of points: %1</p>\n" ).arg( count );
     145                 :          0 :       out << QObject::tr( "<p>Z-Score: %1</p>\n" ).arg( zScore, 0, 'f', 11 );
     146                 :          0 :       out << QStringLiteral( "</body></html>" );
     147                 :            : 
     148                 :          0 :       outputs.insert( QStringLiteral( "OUTPUT_HTML_FILE" ), outputFile );
     149                 :          0 :     }
     150                 :          0 :   }
     151                 :            : 
     152                 :          0 :   return outputs;
     153                 :          0 : }
     154                 :            : 
     155                 :            : ///@endcond