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Algorithms and other processing code should use this method (instead of dataobjects.getLayerFromString) to retrieve layers from a string, as it considers the processing context and allows resolving strings to temporarily stored layers. This permits processing models to function correctly when intermediate results are stored as memory layers. Subsequent model algorithms can then access these temporary layers as inputs. All temporary layers will be removed when the context object is destroyed after the model algorithm is run.
107 lines
4.5 KiB
Python
107 lines
4.5 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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StatisticsByCategories.py
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---------------------
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Date : September 2012
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Copyright : (C) 2012 by Victor Olaya
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Email : volayaf at gmail dot com
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***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************
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"""
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from builtins import str
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__author__ = 'Victor Olaya'
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__date__ = 'September 2012'
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__copyright__ = '(C) 2012, Victor Olaya'
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# This will get replaced with a git SHA1 when you do a git archive
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__revision__ = '$Format:%H$'
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from qgis.core import (QgsApplication,
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QgsStatisticalSummary,
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QgsProcessingUtils)
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from processing.core.outputs import OutputTable
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from processing.core.GeoAlgorithm import GeoAlgorithm
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from processing.tools import dataobjects, vector
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from processing.core.parameters import ParameterVector
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from processing.core.parameters import ParameterTableField
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class StatisticsByCategories(GeoAlgorithm):
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INPUT_LAYER = 'INPUT_LAYER'
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VALUES_FIELD_NAME = 'VALUES_FIELD_NAME'
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CATEGORIES_FIELD_NAME = 'CATEGORIES_FIELD_NAME'
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OUTPUT = 'OUTPUT'
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def icon(self):
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return QgsApplication.getThemeIcon("/providerQgis.svg")
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def svgIconPath(self):
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return QgsApplication.iconPath("providerQgis.svg")
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def group(self):
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return self.tr('Vector table tools')
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def name(self):
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return 'statisticsbycategories'
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def displayName(self):
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return self.tr('Statistics by categories')
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def defineCharacteristics(self):
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self.addParameter(ParameterVector(self.INPUT_LAYER,
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self.tr('Input vector layer')))
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self.addParameter(ParameterTableField(self.VALUES_FIELD_NAME,
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self.tr('Field to calculate statistics on'),
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self.INPUT_LAYER, ParameterTableField.DATA_TYPE_NUMBER))
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self.addParameter(ParameterTableField(self.CATEGORIES_FIELD_NAME,
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self.tr('Field with categories'),
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self.INPUT_LAYER, ParameterTableField.DATA_TYPE_ANY))
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self.addOutput(OutputTable(self.OUTPUT, self.tr('Statistics by category')))
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def processAlgorithm(self, context, feedback):
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layer = dataobjects.QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT_LAYER), context)
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valuesFieldName = self.getParameterValue(self.VALUES_FIELD_NAME)
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categoriesFieldName = self.getParameterValue(self.CATEGORIES_FIELD_NAME)
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output = self.getOutputFromName(self.OUTPUT)
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valuesField = layer.fields().lookupField(valuesFieldName)
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categoriesField = layer.fields().lookupField(categoriesFieldName)
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features = QgsProcessingUtils.getFeatures(layer, context)
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total = 100.0 / QgsProcessingUtils.featureCount(layer, context)
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values = {}
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for current, feat in enumerate(features):
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feedback.setProgress(int(current * total))
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attrs = feat.attributes()
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try:
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value = float(attrs[valuesField])
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cat = str(attrs[categoriesField])
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if cat not in values:
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values[cat] = []
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values[cat].append(value)
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except:
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pass
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fields = ['category', 'min', 'max', 'mean', 'stddev', 'sum', 'count']
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writer = output.getTableWriter(fields)
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stat = QgsStatisticalSummary(QgsStatisticalSummary.Min | QgsStatisticalSummary.Max |
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QgsStatisticalSummary.Mean | QgsStatisticalSummary.StDevSample |
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QgsStatisticalSummary.Sum | QgsStatisticalSummary.Count)
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for (cat, v) in list(values.items()):
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stat.calculate(v)
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record = [cat, stat.min(), stat.max(), stat.mean(), stat.sampleStDev(), stat.sum(), stat.count()]
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writer.addRecord(record)
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