CODEWITHSUNDEEP
pythonpolygonintersectionqgis
krizz
krizz

Reputation: 125

Find neighbouring polygons in Python QGIS

I am using code I found and slightly modified for my purposes. The problem is, it is not doing exactly what I want, and I am stuck with what to change to fix it.

I am searching for all neighbouring polygons, that share common borded (a line), that is not a pointenter image description here

My goal: 135/12 is neigbour with 319/2 135/4, 317 but not with 320/1

What I get in my QGIS table after I run my script

enter image description here

NEIGBOURS are the neighbouring polygons,

SUM is the number of neighbouring polygons

The code I use also includes 320/1 as a neighbouring polygon. How to fix it?

    from qgis.utils import iface
    from PyQt4.QtCore import QVariant
    _NAME_FIELD = 'Nr'
    _SUM_FIELD = 'calc'
    _NEW_NEIGHBORS_FIELD = 'NEIGHBORS'
    _NEW_SUM_FIELD = 'SUM'
    layer = iface.activeLayer()
    layer.startEditing()
    layer.dataProvider().addAttributes(
            [QgsField(_NEW_NEIGHBORS_FIELD, QVariant.String),
             QgsField(_NEW_SUM_FIELD, QVariant.Int)])
    layer.updateFields()
    feature_dict = {f.id(): f for f in layer.getFeatures()}

    index = QgsSpatialIndex()
    for f in feature_dict.values():
        index.insertFeature(f)
    for f in feature_dict.values():
        print 'Working on %s' % f[_NAME_FIELD]
        geom = f.geometry()

        intersecting_ids = index.intersects(geom.boundingBox())

        neighbors = []
        neighbors_sum = 0
        for intersecting_id in intersecting_ids:
            intersecting_f = feature_dict[intersecting_id]

            if (f != intersecting_f and
                not intersecting_f.geometry().disjoint(geom)):
                neighbors.append(intersecting_f[_NAME_FIELD])
                neighbors_sum += intersecting_f[_SUM_FIELD]
        f[_NEW_NEIGHBORS_FIELD] = ','.join(neighbors)
        f[_NEW_SUM_FIELD] = neighbors_sum
        layer.updateFeature(f)

    layer.commitChanges()
    print 'Processing complete.'

Upvotes: 0

Views: 1433

Answers (1)

krizz
krizz

Reputation: 125

I have found somewhat a workaround for it. Before using my script, I create a small (for my purposes, 0,01 m was enough) buffer around all joints. Later, I use a Difference tool to remove the buffer areas from my main layer, thus removing not-needed neighbouring polygons. Using the code now works fine

Upvotes: 1

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