A count of points within a set distance using updatecursor

Question

I have a script that calculates the average distance between points. What I want is to rewrite it so I can input the point layer, input a distance, and the output field will tell me a count of the number of points at that distance. Can anyone help? so basically I just want a script that will tell me a count of the number of points from a point at a certain distance.

#Import standard library modules
import sys, string, arcpy

    inputFC = arcpy.GetParameterAsText(0)# Input Point Layer
    inputdistance = arcpy.GetParameterAsText(1) #input distance
    outputfield = arcpy.GetParameterAsText(1) #output field

# Read the point data into list.  
#
    xs = []
    ys = []
 rowCursor = arcpy.SearchCursor(inputFC)
 for row in rowCursor:
    geom = row.getValue (properties.shapeFieldName)
    cen = geom.centroid
    xs.append(cen.X)
    ys.append(cen.Y)
 del rowCursor

 # compute distance 
 sumdist = 0.0
 count = 0.0
 for i in range(0,len(xs)):
    for j in range(i,len(xs)):
        if (i <> j):
           dist = ((xs[i] -xs[j])**2 + (ys[i] - ys[j])**2)**0.5
           sumdist = sumdist + dist
           count = count + 1
  print "The average inter-point distance is " + str(sumdist/count)
  arcpy.AddMessage("The average inter-point distance is " + str(sumdist/count))

With the following script. Ive tried to run it as Distance.add_nearby_points_count_field('gauges.shp', 100)

 import sys
 import arcpy
 import math

def add_nearby_points_count_field(inputFC, inputdistance):

# Read the point data into list.
coord_pairs = []
desc = arcpy.Describe(inputFC)
rowCursor = arcpy.SearchCursor(inputFC)
for row in rowCursor:
    geom = row.getValue(desc.shapeFieldName)
    coord_pairs.append(geom.centroid)

# Add a field called 'cnt' and calculate nearby points
arcpy.AddField_management(inputFC, 'cnt', 'LONG') #i also tried cutting   out this part and creating the "cnt" field manually
rowCursor = arcpy.UpdateCursor(inputFC)
for row in rowCursor:
    geom = row.getValue(desc.shapeFieldName)
    from_point = geom.centroid
    near_pts = 0
    for to_point in coord_pairs:
        distance = math.sqrt(pow((to_point.X - from_point.X), 2) + pow((to_point.Y - from_point.Y), 2))
        if distance <= inputdistance:
            near_pts += 1
    row.cnt = near_pts - 1 # Subtract 1 to remove the measurement to itself
    rowCursor.updateRow(row)
del rowCursor

if __name__ == '__main__':
    inputFC ='guages.shp' #originally its a featureclass but I converted it to a shapefile to try both methods
    inputdistance = 100
    add_nearby_points_count_field(inputFC, inputdistance)

Answer 1

EDIT based on comment...

Kinn, you can use this in a number of ways. One way is to save the script as "count_nearby_points.py", and as long as it is in your python path, you can use it in any other script by importing it.

import count_nearby_points

Then you should be able to call the count_nearby_points.add_nearby_points_count_field(inputFC, inputdistance) function from within your script.

Or, if you run this script directly, you can modify the parameters under if __name__ == '__main__':

You can also copy the part(s) that you want into your own script.

Feel free to ask if you have further questions.

#-------------------------------------------------------------------------------
# Name:        count_nearby_points.py
#
# Purpose:     Return a count of nearby point features
#
# Created:     29/09/2011
#-------------------------------------------------------------------------------
#!/usr/bin/env python

import sys
import arcpy
import math

def add_nearby_points_count_field(inputFC, inputdistance):

    # Read the point data into list.
    coord_pairs = []
    desc = arcpy.Describe(inputFC)
    rowCursor = arcpy.SearchCursor(inputFC)
    for row in rowCursor:
        geom = row.getValue(desc.shapeFieldName)
        coord_pairs.append(geom.centroid)

    # Add a field called 'cnt' and calculate nearby points
    arcpy.AddField_management(inputFC, 'cnt', 'LONG')
    rowCursor = arcpy.UpdateCursor(inputFC)
    for row in rowCursor:
        geom = row.getValue(desc.shapeFieldName)
        from_point = geom.centroid
        near_pts = 0
        for to_point in coord_pairs:
            distance = math.sqrt(pow((to_point.X - from_point.X), 2) + pow((to_point.Y - from_point.Y), 2))
            if distance <= inputdistance:
                near_pts += 1
        row.cnt = near_pts - 1 # Subtract 1 to remove the measurement to itself
        rowCursor.updateRow(row)
    del rowCursor

if __name__ == '__main__':
    # Test data for when running as __main__, make sure that 'points.shp' exists.
    inputFC ='points.shp'
    inputdistance = 100
    add_nearby_points_count_field(inputFC, inputdistance)