natural_cities script added

scripts/nat_cities.py

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+#----------------------------------------------------------------------------------------
+# Natural Cities Algorithm                                                              #
+#                                                                                       #
+# Creates Natural City polygons out of input point vector file                          #
+# more Information on methodology:                                                      #
+#   *jiang/miao 2014:  https://arxiv.org/pdf/1401.6756.pdf                              #
+#   *jiang 2015: https://www.sciencedirect.com/science/article/pii/S026427511400198X    #
+#                                                                                       #
+#  requires saga and python-shapely                                                     #
+#----------------------------------------------------------------------------------------
+
+##natural_cities=name
+##points=vector
+##linelength=output vector
+##natural_cities=output vector
+##outputCRS=crs
+
+# create tin
+tin=processing.runalg('qgis:delaunaytriangulation', points,None)
+
+# convert tin-polygons to lines
+polygonToLines=processing.runalg('qgis:polygonstolines', tin['OUTPUT'],None)
+
+# explode lines
+explodeLines=processing.runalg('qgis:explodelines', polygonToLines['OUTPUT'],None)
+
+# delete duplicates
+deleteDup=processing.runalg('qgis:deleteduplicategeometries', explodeLines['OUTPUT'],None)
+
+# reproject for statistics
+reproj=processing.runalg('qgis:reprojectlayer', deleteDup['OUTPUT'],outputCRS,None)
+
+#get lineproperties (requires saga geoalgorithms)
+lineProp=processing.runalg('saga:lineproperties', reproj['OUTPUT'],False,False,True,linelength)
+
+#calc basic statistics
+basicStat=processing.runalg('qgis:basicstatisticsfornumericfields', lineProp['OUTPUT'],'length',None)
+
+# extract mean (=cut-off-value)
+extractbyAttribute=processing.runalg('qgis:extractbyattribute', lineProp['OUTPUT'],'length',4,basicStat['MEAN'],None)
+
+# create polgons out of line (requires python-shapely)
+polygonize=processing.runalg('qgis:polygonize',extractbyAttribute['OUTPUT'],False,True,None)
+
+# dissolve 
+diss=processing.runalg('qgis:dissolve', polygonize['OUTPUT'],True,None,None)
+
+# multipartsToSingleParts
+mtoSParts=processing.runalg('qgis:multiparttosingleparts', diss['OUTPUT'],natural_cities)
+

scripts/nat_cities.py.help

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+{"linelength": "", "ALG_DESC": "Creates Natural City polygons out of input point vector file                          \n\nmore Information on methodology:                                                      \njiang/miao 2014:  https://arxiv.org/pdf/1401.6756.pdf                              \njiang 2015: https://www.sciencedirect.com/science/article/pii/S026427511400198X\n\n#  requires saga and python-shapely              ", "line_cropped": "", "ALG_CREATOR": "https://github.com/niels-flohr", "outputCRS": "choose output crs", "points": "requires point shapefile", "ALG_VERSION": "1", "ALG_HELP_CREATOR": "", "natural_cities": "natural cities polygon shapefile"}