1

I am currently writing an Python Script within QGIS to connect points of two specific point layers:

Attributes of point layer 1:

enter image description here

Attributes of point layer 2:

enter image description here

For each point in point-layer1, the python script loops over all points of point-layer2 and compares the attribut "direction" (of point-layer1) with the attribut "location" (of point-layer2). If they are equal, a new line should be created and stored into the output line-layer (together with the lineID (a line counter) and the direction name + location name).

Here is my Python Script:

# name : ConnectPointsByValue_script
# date : 27.12.2017
# description: connects points from evis with points of location_coordinates
#       if the attributes "direction" and "location" are equal

from PyQt4.QtCore import QVariant
from qgis.core import *
from PyQt4.QtCore import *

#***********Constants
#
LINEID = 'lineID'
POINTID1 = 'pointID_Location'
POINTID2 = 'pointID_Direction'
#
#***********

# input parameters 
##Counters=vector
##Locations=vector

inputLayerCounters = processing.getObject(Counters)
inputLayerLocations = processing.getObject(Locations)

crs = inputLayerCounters.crs().toWkt()


# Create the output layer
outLayer = QgsVectorLayer('Linestring?crs='+ crs, 'connector_lines2' , 
'memory')
outdp = outLayer.dataProvider()


#get the field index
outLineID = outdp.fieldNameIndex(LINEID)
outID1 = outdp.fieldNameIndex(POINTID1)
outID2 = outdp.fieldNameIndex(POINTID2)
lineIDcnt = 0


# loop through points of iCounters and connect each point with the matching 
location point
for feat1 in inputLayerCounters.getFeatures():
   geom1 = feat1.geometry()

   #loop all points from iLocations
   for feat2 in inputLayerLocations.getFeatures():
      geom2 = feat2.geometry()

      # get the feature's attributes
      attrs1 = feat1.attributes()
      idx1 = inputLayerCounters.fieldNameIndex('direction')
      attrs2 = feat2.attributes()
      idx2 = inputLayerLocations.fieldNameIndex('location')

      #check if attributes are equal
      if feat1.attributes()[idx1] == feat2.attributes()[idx2]:
          lineIDcnt +=  1

          #if true: create line and add to output line layer
          connector = QgsFeature(outLayer.pendingFields())
          connector.setGeometry(QgsGeometry.fromPolyline([geom1.asPoint(),
                                                    geom2.asPoint()]))

          #record the IDs
          res = connector.setAttribute(outLineID, lineIDcnt)
          res = connector.setAttribute(outID1, feat1.attributes()[idx1])
          res = connector.setAttribute(outID2, feat2.attributes()[idx2])

          #add the feature to the layer
          res = outdp.addFeatures([connector])


 # Add the layer to the Layers panel
 QgsMapLayerRegistry.instance().addMapLayer(outLayer)

 print "Done .. "

If I execute this script, I get an error which says:

attribute index -1 out of bounds [0;0]

I think I am doing something wrong with indexing the attributes of my points. Any suggestions on how to solve this?

2

It does not look like you are adding attributes to your memory layer, try:

from PyQt4.QtCore import QVariant
# Create the output layer
outLayer = QgsVectorLayer('Linestring?crs='+ crs, 'connector_lines2' , 
'memory')
outLayer.startEditing()
outLayer.dataProvider().addAttributes( [ QgsField("lineID", QVariant.String), QgsField("pointID_Location",QVariant.String),QgsField("pointID_Direction",QVariant.String)])
outLayer.updateFields()
outLayer.commitChanges()

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.