QGIS API Documentation 3.39.0-Master (67e056379ed)
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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
22QString QgsAddUniqueValueIndexAlgorithm::name() const
23{
24 return QStringLiteral( "adduniquevalueindexfield" );
25}
26
27QString QgsAddUniqueValueIndexAlgorithm::displayName() const
28{
29 return QObject::tr( "Add unique value index field" );
30}
31
32QStringList QgsAddUniqueValueIndexAlgorithm::tags() const
33{
34 return QObject::tr( "categorize,categories,category,reclassify,classes,create" ).split( ',' );
35}
36
37QString QgsAddUniqueValueIndexAlgorithm::group() const
38{
39 return QObject::tr( "Vector table" );
40}
41
42QString QgsAddUniqueValueIndexAlgorithm::groupId() const
43{
44 return QStringLiteral( "vectortable" );
45}
46
47void QgsAddUniqueValueIndexAlgorithm::initAlgorithm( const QVariantMap & )
48{
49 addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ), QObject::tr( "Input layer" ),
50 QList< int >() << static_cast< int >( Qgis::ProcessingSourceType::Vector ) ) );
51 addParameter( new QgsProcessingParameterField( QStringLiteral( "FIELD" ), QObject::tr( "Class field" ), QVariant(),
52 QStringLiteral( "INPUT" ), Qgis::ProcessingFieldParameterDataType::Any ) );
53 addParameter( new QgsProcessingParameterString( QStringLiteral( "FIELD_NAME" ),
54 QObject::tr( "Output field name" ), QStringLiteral( "NUM_FIELD" ) ) );
55
56 std::unique_ptr< QgsProcessingParameterFeatureSink > classedOutput = std::make_unique< QgsProcessingParameterFeatureSink >( QStringLiteral( "OUTPUT" ), QObject::tr( "Layer with index field" ), Qgis::ProcessingSourceType::VectorAnyGeometry, QVariant(), true );
57 classedOutput->setCreateByDefault( true );
58 addParameter( classedOutput.release() );
59
60 std::unique_ptr< QgsProcessingParameterFeatureSink > summaryOutput = std::make_unique< QgsProcessingParameterFeatureSink >( QStringLiteral( "SUMMARY_OUTPUT" ), QObject::tr( "Class summary" ),
61 Qgis::ProcessingSourceType::Vector, QVariant(), true );
62 summaryOutput->setCreateByDefault( false );
63 addParameter( summaryOutput.release() );
64}
65
66QString 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
74QgsAddUniqueValueIndexAlgorithm *QgsAddUniqueValueIndexAlgorithm::createInstance() const
75{
76 return new QgsAddUniqueValueIndexAlgorithm();
77}
78
79QVariantMap 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 const QString newFieldName = parameterAsString( parameters, QStringLiteral( "FIELD_NAME" ), context );
86 QgsFields fields = source->fields();
87 const QgsField newField = QgsField( newFieldName, QMetaType::Type::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 const QString sourceFieldName = parameterAsString( parameters, QStringLiteral( "FIELD" ), context );
94 const 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, Qgis::WkbType::NoGeometry ) );
103
104 QHash< QVariant, int > classes;
105
107
108 const long count = source->featureCount();
109 const 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 const 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 if ( !sink->addFeature( feature, QgsFeatureSink::FastInsert ) )
134 throw QgsProcessingException( writeFeatureError( sink.get(), parameters, QStringLiteral( "OUTPUT" ) ) );
135 }
136
137 feedback->setProgress( current * step );
138 current++;
139 }
140
141 if ( summarySink )
142 {
143 //generate summary table - first we make a sorted version of the classes
144 QMap< int, QVariant > sorted;
145 for ( auto classIt = classes.constBegin(); classIt != classes.constEnd(); ++classIt )
146 {
147 sorted.insert( classIt.value(), classIt.key() );
148 }
149 // now save them
150 for ( auto sortedIt = sorted.constBegin(); sortedIt != sorted.constEnd(); ++sortedIt )
151 {
152 QgsFeature f;
153 f.setAttributes( QgsAttributes() << sortedIt.key() << sortedIt.value() );
154 if ( !summarySink->addFeature( f, QgsFeatureSink::FastInsert ) )
155 throw QgsProcessingException( writeFeatureError( summarySink.get(), parameters, QStringLiteral( "SUMMARY_OUTPUT" ) ) );
156 }
157 }
158
159 QVariantMap results;
160 if ( sink )
161 results.insert( QStringLiteral( "OUTPUT" ), dest );
162 if ( summarySink )
163 results.insert( QStringLiteral( "SUMMARY_OUTPUT" ), summaryDest );
164 return results;
165}
166
@ Vector
Tables (i.e. vector layers with or without geometry). When used for a sink this indicates the sink ha...
@ VectorAnyGeometry
Any vector layer with geometry.
@ SkipGeometryValidityChecks
Invalid geometry checks should always be skipped. This flag can be useful for algorithms which always...
@ NoGeometry
No geometry.
A vector of attributes.
Wrapper for iterator of features from vector data provider or vector layer.
bool nextFeature(QgsFeature &f)
Fetch next feature and stores in f, returns true on success.
This class wraps a request for features to a vector layer (or directly its vector data provider).
@ FastInsert
Use faster inserts, at the cost of updating the passed features to reflect changes made at the provid...
The feature class encapsulates a single feature including its unique ID, geometry and a list of field...
Definition qgsfeature.h:58
QgsAttributes attributes
Definition qgsfeature.h:67
void setAttributes(const QgsAttributes &attrs)
Sets the feature's attributes.
bool isCanceled() const
Tells whether the operation has been canceled already.
Definition qgsfeedback.h:53
void setProgress(double progress)
Sets the current progress for the feedback object.
Definition qgsfeedback.h:61
Encapsulate a field in an attribute table or data source.
Definition qgsfield.h:53
Container of fields for a vector layer.
Definition qgsfields.h:46
bool append(const QgsField &field, Qgis::FieldOrigin origin=Qgis::FieldOrigin::Provider, int originIndex=-1)
Appends a field.
Definition qgsfields.cpp:69
Contains information about the context in which a processing algorithm is executed.
Custom exception class for processing related exceptions.
Base class for providing feedback from a processing algorithm.
An input feature source (such as vector layers) parameter for processing algorithms.
A vector layer or feature source field parameter for processing algorithms.
A string parameter for processing algorithms.