QGIS API Documentation  3.8.0-Zanzibar (11aff65)
qgsalgorithmuniquevalueindex.cpp
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1 /***************************************************************************
2  qgsalgorithmuniquevalueindex.cpp
3  ---------------------
4  begin : January 2018
5  copyright : (C) 2018 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 
19 
21 
22 QString QgsAddUniqueValueIndexAlgorithm::name() const
23 {
24  return QStringLiteral( "adduniquevalueindexfield" );
25 }
26 
27 QString QgsAddUniqueValueIndexAlgorithm::displayName() const
28 {
29  return QObject::tr( "Add unique value index field" );
30 }
31 
32 QStringList QgsAddUniqueValueIndexAlgorithm::tags() const
33 {
34  return QObject::tr( "categorize,categories,category,reclassify,classes,create" ).split( ',' );
35 }
36 
37 QString QgsAddUniqueValueIndexAlgorithm::group() const
38 {
39  return QObject::tr( "Vector table" );
40 }
41 
42 QString QgsAddUniqueValueIndexAlgorithm::groupId() const
43 {
44  return QStringLiteral( "vectortable" );
45 }
46 
47 void QgsAddUniqueValueIndexAlgorithm::initAlgorithm( const QVariantMap & )
48 {
49  addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ), QObject::tr( "Input layer" ),
50  QList< int >() << QgsProcessing::TypeVector ) );
51  addParameter( new QgsProcessingParameterField( QStringLiteral( "FIELD" ), QObject::tr( "Class field" ), QVariant(),
52  QStringLiteral( "INPUT" ), QgsProcessingParameterField::Any ) );
53  addParameter( new QgsProcessingParameterString( QStringLiteral( "FIELD_NAME" ),
54  QObject::tr( "Output field name" ), QStringLiteral( "NUM_FIELD" ) ) );
55 
56  std::unique_ptr< QgsProcessingParameterFeatureSink > classedOutput = qgis::make_unique< QgsProcessingParameterFeatureSink >( QStringLiteral( "OUTPUT" ), QObject::tr( "Layer with index field" ), QgsProcessing::TypeVectorAnyGeometry, QVariant(), true );
57  classedOutput->setCreateByDefault( true );
58  addParameter( classedOutput.release() );
59 
60  std::unique_ptr< QgsProcessingParameterFeatureSink > summaryOutput = qgis::make_unique< QgsProcessingParameterFeatureSink >( QStringLiteral( "SUMMARY_OUTPUT" ), QObject::tr( "Class summary" ),
61  QgsProcessing::TypeVector, QVariant(), true );
62  summaryOutput->setCreateByDefault( false );
63  addParameter( summaryOutput.release() );
64 }
65 
66 QString QgsAddUniqueValueIndexAlgorithm::shortHelpString() const
67 {
68  return QObject::tr( "This algorithm takes a vector layer and an attribute and adds a new numeric field. Values in this field correspond to values in the specified attribute, so features with the same "
69  "value for the attribute will have the same value in the new numeric field. This creates a numeric equivalent of the specified attribute, which defines the same classes.\n\n"
70  "The new attribute is not added to the input layer but a new layer is generated instead.\n\n"
71  "Optionally, a separate table can be output which contains a summary of the class field values mapped to the new unique numeric value." );
72 }
73 
74 QgsAddUniqueValueIndexAlgorithm *QgsAddUniqueValueIndexAlgorithm::createInstance() const
75 {
76  return new QgsAddUniqueValueIndexAlgorithm();
77 }
78 
79 QVariantMap QgsAddUniqueValueIndexAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
80 {
81  std::unique_ptr< QgsProcessingFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
82  if ( !source )
83  throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
84 
85  QString newFieldName = parameterAsString( parameters, QStringLiteral( "FIELD_NAME" ), context );
86  QgsFields fields = source->fields();
87  QgsField newField = QgsField( newFieldName, QVariant::Int );
88  fields.append( newField );
89 
90  QString dest;
91  std::unique_ptr< QgsFeatureSink > sink( parameterAsSink( parameters, QStringLiteral( "OUTPUT" ), context, dest, fields, source->wkbType(), source->sourceCrs() ) );
92 
93  QString sourceFieldName = parameterAsString( parameters, QStringLiteral( "FIELD" ), context );
94  int fieldIndex = source->fields().lookupField( sourceFieldName );
95  if ( fieldIndex < 0 )
96  throw QgsProcessingException( QObject::tr( "Invalid field name %1" ).arg( sourceFieldName ) );
97 
98  QString summaryDest;
99  QgsFields summaryFields;
100  summaryFields.append( newField );
101  summaryFields.append( source->fields().at( fieldIndex ) );
102  std::unique_ptr< QgsFeatureSink > summarySink( parameterAsSink( parameters, QStringLiteral( "SUMMARY_OUTPUT" ), context, summaryDest, summaryFields, QgsWkbTypes::NoGeometry ) );
103 
104  QHash< QVariant, int > classes;
105 
107 
108  long count = source->featureCount();
109  double step = count > 0 ? 100.0 / count : 1;
110  int current = 0;
111  QgsFeature feature;
112  while ( it.nextFeature( feature ) )
113  {
114  if ( feedback->isCanceled() )
115  {
116  break;
117  }
118 
119  QgsAttributes attributes = feature.attributes();
120  QVariant clazz = attributes.at( fieldIndex );
121 
122  int thisValue = classes.value( clazz, -1 );
123  if ( thisValue == -1 )
124  {
125  thisValue = classes.count();
126  classes.insert( clazz, thisValue );
127  }
128 
129  if ( sink )
130  {
131  attributes.append( thisValue );
132  feature.setAttributes( attributes );
133  sink->addFeature( feature, QgsFeatureSink::FastInsert );
134  }
135 
136  feedback->setProgress( current * step );
137  current++;
138  }
139 
140  if ( summarySink )
141  {
142  //generate summary table - first we make a sorted version of the classes
143  QMap< int, QVariant > sorted;
144  for ( auto classIt = classes.constBegin(); classIt != classes.constEnd(); ++classIt )
145  {
146  sorted.insert( classIt.value(), classIt.key() );
147  }
148  // now save them
149  for ( auto sortedIt = sorted.constBegin(); sortedIt != sorted.constEnd(); ++sortedIt )
150  {
151  QgsFeature f;
152  f.setAttributes( QgsAttributes() << sortedIt.key() << sortedIt.value() );
153  summarySink->addFeature( f, QgsFeatureSink::FastInsert );
154  }
155  }
156 
157  QVariantMap results;
158  if ( sink )
159  results.insert( QStringLiteral( "OUTPUT" ), dest );
160  if ( summarySink )
161  results.insert( QStringLiteral( "SUMMARY_OUTPUT" ), summaryDest );
162  return results;
163 }
164 
Wrapper for iterator of features from vector data provider or vector layer.
Use faster inserts, at the cost of updating the passed features to reflect changes made at the provid...
Base class for providing feedback from a processing algorithm.
Invalid geometry checks should always be skipped. This flag can be useful for algorithms which always...
A vector layer or feature source field parameter for processing algorithms.
void setProgress(double progress)
Sets the current progress for the feedback object.
Definition: qgsfeedback.h:63
Container of fields for a vector layer.
Definition: qgsfields.h:42
void setAttributes(const QgsAttributes &attrs)
Sets the feature&#39;s attributes.
Definition: qgsfeature.cpp:127
The feature class encapsulates a single feature including its id, geometry and a list of field/values...
Definition: qgsfeature.h:55
This class wraps a request for features to a vector layer (or directly its vector data provider)...
Custom exception class for processing related exceptions.
Definition: qgsexception.h:82
bool append(const QgsField &field, FieldOrigin origin=OriginProvider, int originIndex=-1)
Appends a field. The field must have unique name, otherwise it is rejected (returns false) ...
Definition: qgsfields.cpp:59
Encapsulate a field in an attribute table or data source.
Definition: qgsfield.h:48
bool isCanceled() const
Tells whether the operation has been canceled already.
Definition: qgsfeedback.h:54
An input feature source (such as vector layers) parameter for processing algorithms.
Tables (i.e. vector layers with or without geometry). When used for a sink this indicates the sink ha...
Definition: qgsprocessing.h:53
bool nextFeature(QgsFeature &f)
A vector of attributes.
Definition: qgsattributes.h:57
Contains information about the context in which a processing algorithm is executed.
A string parameter for processing algorithms.
Any vector layer with geometry.
Definition: qgsprocessing.h:47
QgsAttributes attributes
Definition: qgsfeature.h:65