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118 lines
3.7 KiB
Python
118 lines
3.7 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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vector.py
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---------------------
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Date : February 2013
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Copyright : (C) 2013 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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__author__ = 'Victor Olaya'
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__date__ = 'February 2013'
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__copyright__ = '(C) 2013, 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 (NULL,
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QgsFeatureRequest)
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def resolveFieldIndex(source, attr):
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"""This method takes an object and returns the index field it
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refers to in a layer. If the passed object is an integer, it
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returns the same integer value. If the passed value is not an
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integer, it returns the field whose name is the string
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representation of the passed object.
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Ir raises an exception if the int value is larger than the number
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of fields, or if the passed object does not correspond to any
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field.
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"""
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if isinstance(attr, int):
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return attr
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else:
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index = source.fields().lookupField(attr)
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if index == -1:
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raise ValueError('Wrong field name')
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return index
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def values(source, *attributes):
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"""Returns the values in the attributes table of a feature source,
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for the passed fields.
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Field can be passed as field names or as zero-based field indices.
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Returns a dict of lists, with the passed field identifiers as keys.
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It considers the existing selection.
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It assummes fields are numeric or contain values that can be parsed
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to a number.
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"""
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ret = {}
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indices = []
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attr_keys = {}
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for attr in attributes:
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index = resolveFieldIndex(source, attr)
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indices.append(index)
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attr_keys[index] = attr
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# use an optimised feature request
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request = QgsFeatureRequest().setSubsetOfAttributes(indices).setFlags(QgsFeatureRequest.NoGeometry)
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for feature in source.getFeatures(request):
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for i in indices:
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# convert attribute value to number
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try:
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v = float(feature.attributes()[i])
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except:
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v = None
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k = attr_keys[i]
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if k in ret:
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ret[k].append(v)
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else:
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ret[k] = [v]
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return ret
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def convert_nulls(values, replacement=None):
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"""
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Converts NULL items in a list of values to a replacement value (usually None)
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:param values: list of values
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:param replacement: value to use in place of NULL
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:return: converted list
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"""
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return [i if i != NULL else replacement for i in values]
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def checkMinDistance(point, index, distance, points):
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"""Check if distance from given point to all other points is greater
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than given value.
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"""
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if distance == 0:
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return True
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neighbors = index.nearestNeighbor(point, 1)
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if len(neighbors) == 0:
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return True
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if neighbors[0] in points:
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np = points[neighbors[0]]
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if np.sqrDist(point) < (distance * distance):
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return False
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return True
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