How can I transform a polygon into a point?
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11-16-2017 02:24 PM
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by
XanderBakker
In case you do not have access to an Advance license you could create a tool that does this for you with a Basic license.(sorry for the Spanish interface)
- first parameter is the polygon featureclass
- second parameter is the output point featureclass
- third parameter is the method
The code beneath looks like this:
#-------------------------------------------------------------------------------
# Name: FeatureToPoint.py
# Purpose: Convertir feature a punto
#
# Author: xbakker
#
# Created: 02/03/2015
#-------------------------------------------------------------------------------
import arcpy
import os
import math
def main():
# parameters
fc_in = arcpy.GetParameterAsText(0)
fc_out = arcpy.GetParameterAsText(1)
method = arcpy.GetParameterAsText(2) # CENTROID, INSIDE
# fld para poder hacer el join con la entrada
fld_oid_in = "ORIG_FID"
# geometria de salida
geomtype = "POINT"
sr = arcpy.Describe(fc_in).spatialReference
# recreate fc_out based on fc_lines (in)
ws_name, fc_name = os.path.split(fc_out)
createFeatureClass(fc_out, fc_in, geomtype, sr)
# add OID field
arcpy.AddField_management(fc_out, fld_oid_in, "LONG")
# cursors:
cnt = 0
flds_out = ("SHAPE@", fld_oid_in)
with arcpy.da.InsertCursor(fc_out, flds_out) as curs_out:
flds_in =("SHAPE@", "OID@")
with arcpy.da.SearchCursor(fc_in, flds_in) as curs:
for row in curs:
feat = row[0]
oid = row[1]
# get point based on method
pnt = getPoint(feat, method)
# store point
cnt += 1
if cnt % 100 == 0:
arcpy.AddMessage("Procesando feature: {0}".format(cnt))
curs_out.insertRow((pnt, oid, ))
arcpy.AddMessage("{0} features procesados...".format(cnt))
def getPoint(feat, method):
"""Convertir feature a punto dependiendo del metodo y tipo de geometria"""
pnt = None
if method == "CENTROID" and feat.type == 'polygon':
pnt = feat.centroid
elif method == "CENTROID" and feat.type == 'polyline':
pnt = CentroidPolyline(feat)
elif method == "CENTROID" and feat.type == 'multipoint':
# average x and y coordinates of all the points in the multipoint feature
pnt = CentriodMultiPoint(feat)
elif method == "INSIDE" and feat.type == 'polygon':
pnt = feat.labelPoint
elif method == "INSIDE" and feat.type == 'polyline':
pntg = feat.positionAlongLine(0.5, True)
pnt = pntg.firstPoint
elif method == "INSIDE" and feat.type == 'multipoint':
pnt = InsideMultiPoint(feat)
return pnt
def InsideMultiPoint(feat):
# punto mas cercano al centroid
pnt_c = CentriodMultiPoint(feat)
min_dist = 999999
for pnt_mp in feat:
dist = getDistance(pnt_mp, pnt_c)
if dist < min_dist:
pnt = arcpy.Point(pnt_mp.X, pnt_mp.Y)
min_dist = dist
return pnt
def CentriodMultiPoint(multipoint):
lst_x = []
lst_y = []
for pnt in multipoint:
lst_x.append(pnt.X)
lst_y.append(pnt.Y)
return arcpy.Point(sum(lst_x)/float(len(lst_x)), sum(lst_y)/float(len(lst_y)))
def CentroidPolyline(polyline):
"""weighted average x and y coordinates of the midpoints of all line segments in the line feature
where the weight of a particular midpoint is the length of the correspondent line segment"""
lst_x = []
lst_y = []
lst_length = []
for part in polyline:
prev_pnt = None
for pnt_part in part:
if prev_pnt is None:
# skip
prev_pnt = arcpy.Point(pnt_part.X, pnt_part.Y)
else:
dist = getDistance(pnt_part, prev_pnt)
line = arcpy.Polyline(arcpy.Array([prev_pnt, pnt_part]))
mid_pnt = line.positionAlongLine(0.5, True)
lst_x.append(mid_pnt.firstPoint.X * dist)
lst_y.append(mid_pnt.firstPoint.Y * dist)
lst_length.append(dist)
sum_dist = sum(lst_length)
sum_x = sum(lst_x)
sum_y = sum(lst_y)
x = sum_x / sum_dist
y = sum_y / sum_dist
return arcpy.Point(x, y)
def createFeatureClass(fc_out, fc_in, geomtype, sr):
ws_name, fc_name = os.path.split(fc_out)
arcpy.CreateFeatureclass_management(ws_name, fc_name, geomtype, spatial_reference=sr)
def getDistance(pnt1, pnt2):
return math.hypot(pnt1.X - pnt2.X, pnt1.Y - pnt2.Y)
if __name__ == '__main__':
main()
by
I fogot to ask something in my previous reply.
Summing up: I added two fields in the original feature class (contening polygons), I calculated the X and Y coordinates of the centroid, I created a XY event by going to data management tools, layers and table views, make xy event. When I open the attribute table, I find two fields with the shape, and the geometry is polygon. (see attachment). Why is that happening? I can visualize points on the map.
