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alexbruyalexbruy
committedOct 4, 2012
review Nearest neighbour tool
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ltr-3_40Before-merge-new_vector_api
1 parent a796d98 commit ad0ff93

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‎python/plugins/sextante/ftools/NearestNeighbourAnalysis.py

Lines changed: 81 additions & 49 deletions
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from sextante.core.GeoAlgorithm import GeoAlgorithm
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import os.path
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import math
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from PyQt4 import QtGui
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from PyQt4.QtCore import *
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from PyQt4.QtGui import *
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from qgis.core import *
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from sextante.parameters.ParameterVector import ParameterVector
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from sextante.core.GeoAlgorithm import GeoAlgorithm
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from sextante.core.QGisLayers import QGisLayers
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from sextante.ftools import ftools_utils
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import math
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from sextante.parameters.ParameterVector import ParameterVector
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from sextante.outputs.OutputHTML import OutputHTML
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from sextante.outputs.OutputNumber import OutputNumber
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from sextante.ftools import FToolsUtils as utils
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class NearestNeighbourAnalysis(GeoAlgorithm):
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POINTS = "POINTS"
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OUTPUT = "OUTPUT"
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OBSERVED_MD = "OBSERVED_MD"
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EXPECTED_MD = "EXPECTED_MD"
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NN_INDEX = "NN_INDEX"
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POINT_COUNT = "POINT_COUNT"
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Z_SCORE = "Z_SCORE"
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def getIcon(self):
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return QtGui.QIcon(os.path.dirname(__file__) + "/icons/neighbour.png")
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def defineCharacteristics(self):
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self.name = "Nearest neighbour analysis"
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self.group = "Analysis tools"
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self.addParameter(ParameterVector(self.POINTS, "Points", ParameterVector.VECTOR_TYPE_POINT))
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self.addOutput(OutputHTML(self.OUTPUT, "Result"))
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self.addOutput(OutputNumber(self.OBSERVED_MD, "Observed mean distance"))
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self.addOutput(OutputNumber(self.EXPECTED_MD, "Expected mean distance"))
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self.addOutput(OutputNumber(self.NN_INDEX, "Nearest neighbour index"))
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self.addOutput(OutputNumber(self.POINT_COUNT, "Number of points"))
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self.addOutput(OutputNumber(self.Z_SCORE, "Z-Score"))
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def processAlgorithm(self, progress):
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output = self.getOutputValue(NearestNeighbourAnalysis.OUTPUT)
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vlayer = QGisLayers.getObjectFromUri(self.getParameterValue(NearestNeighbourAnalysis.POINTS))
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vprovider = vlayer.dataProvider()
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allAttrs = vprovider.attributeIndexes()
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vprovider.select( allAttrs )
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layer = QGisLayers.getObjectFromUri(self.getParameterValue(self.POINTS))
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output = self.getOutputValue(self.OUTPUT)
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provider = layer.dataProvider()
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spatialIndex = utils.createSpatialIndex(provider)
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provider.rewind()
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provider.select()
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feat = QgsFeature()
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neighbour = QgsFeature()
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sumDist = 0.00
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distance = QgsDistanceArea()
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A = vlayer.extent()
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A = float( A.width() * A.height() )
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index = ftools_utils.createIndex( vprovider )
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vprovider.rewind()
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nFeat = vprovider.featureCount()
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nElement = 0
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while vprovider.nextFeature( feat ):
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neighbourID = index.nearestNeighbor( feat.geometry().asPoint(), 2 )[ 1 ]
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vprovider.featureAtId( neighbourID, neighbour, True, [] )
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nearDist = distance.measureLine( neighbour.geometry().asPoint(), feat.geometry().asPoint() )
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sumDist += nearDist
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nElement += 1
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progress.setPercentage(int(nElement/nFeat * 100))
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nVal = vprovider.featureCount()
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do = float( sumDist) / nVal
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de = float( 0.5 / math.sqrt( nVal / A ) )
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d = float( do / de )
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SE = float( 0.26136 / math.sqrt( ( nVal * nVal ) / A ) )
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zscore = float( ( do - de ) / SE )
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lstStats = []
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lstStats.append("Observed mean distance:" + unicode( do ) )
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lstStats.append("Expected mean distance:" + unicode( de ) )
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lstStats.append("Nearest neighbour index:" + unicode( d ) )
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lstStats.append("N:" + unicode( nVal ) )
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lstStats.append("Z-Score:" + unicode( zscore ) )
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self.createHTML(output, lstStats)
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def createHTML(self, outputFile, lstStats):
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sumDist = 0.00
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A = layer.extent()
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A = float(A.width() * A.height())
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current = 0
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total = 100.0 / float(provider.featureCount())
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while provider.nextFeature( feat ):
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neighbourID = spatialIndex.nearestNeighbor(feat.geometry().asPoint(), 2)[1]
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provider.featureAtId(neighbourID, neighbour, True)
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sumDist += distance.measureLine(neighbour.geometry().asPoint(), feat.geometry().asPoint())
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current += 1
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progress.setPercentage(int(current * total))
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count = provider.featureCount()
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do = float(sumDist) / count
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de = float(0.5 / math.sqrt(count / A))
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d = float(do / de)
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SE = float(0.26136 / math.sqrt(( count ** 2) / A))
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zscore = float((do - de) / SE)
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data = []
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data.append("Observed mean distance: " + unicode(do))
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data.append("Expected mean distance: " + unicode(de))
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data.append("Nearest neighbour index: " + unicode(d))
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data.append("Number of points: " + unicode(count))
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data.append("Z-Score: " + unicode(zscore))
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self.createHTML(output, data)
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self.setOutputValue(self.OBSERVED_MD, float( data[ 0 ].split( ": " )[ 1 ] ) )
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self.setOutputValue(self.EXPECTED_MD, float( data[ 1 ].split( ": " )[ 1 ] ) )
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self.setOutputValue(self.NN_INDEX, float( data[ 2 ].split( ": " )[ 1 ] ) )
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self.setOutputValue(self.POINT_COUNT, float( data[ 3 ].split( ": " )[ 1 ] ) )
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self.setOutputValue(self.Z_SCORE, float( data[ 4 ].split( ": " )[ 1 ] ) )
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def createHTML(self, outputFile, algData):
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f = open(outputFile, "w")
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for s in lstStats:
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for s in algData:
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f.write("<p>" + str(s) + "</p>")
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f.close()
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def defineCharacteristics(self):
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self.name = "Nearest neighbour analysis"
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self.group = "Analysis tools"
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self.addParameter(ParameterVector(NearestNeighbourAnalysis.POINTS, "Points", ParameterVector.VECTOR_TYPE_POINT))
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self.addOutput(OutputHTML(NearestNeighbourAnalysis.OUTPUT, "Result"))

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