[GIS] selecting a percentage (75%) of a group of points based on the distance from one separate point in ArcGIS

arcgis-10.0spatial statistics

This is ArcGIS specific.

I have 2 point shapefiles A and B, the first one (A) is a single point that contains a lat long, the second (B) is a multitude of points (over 12k) that each contain their lat and long. What I am trying to do is to automate the selection of 75% of shapefile B's points based on the distance from shapefile A. In other words I want to select the nearest 75% of shapefile B points to shapefile A's one point.

Best Answer

You could make a Multiple Ring Buffer on shapefile A, and then do a spatial join of the Buffer to shapefile B. When you do a spatial join of polygons and points, you get a count of the number of points in each polygon in the attribute table of the join. Then, by examining the total number of points within the buffers, you can get within 75% of the points in shapefile B.

A slightly different approach would be to script this in Python, and check for the 75% in a loop, but if it is a once off calculation you may not need that.

Related Solutions

[GIS] Updating Lat/Longs and actual position of point shapefile using arcpy.UpdateCursor()

It sounds like you're updating some attributes of your features instead of updating the actual geometry. You can make changes to a feature's geometry using python but it's a couple extra lines of code. Check out this example:

import arcpy
shapeName = arcpy.Describe('c:/path/to/shp/update_geom.shp').shapeFieldName
rows = arcpy.UpdateCursor(r'c:/path/to/shp/update_geom.shp')
row = rows.next() # just one row...you could iterate through all rows
pnt = arcpy.Point(row.getValue(shapeName).getPart(0).X + 0.5, row.getValue(shapeName).getPart(0).Y + 0.5)
row.setValue(shapeName, pnt)
rows.updateRow(row)
del rows

That only updates one row but demonstrates how to update a point feature's geometry.

**Added code that loops over all rows.

import arcpy
shapeName = arcpy.Describe('c:/path/to/shp/update_geom.shp').shapeFieldName
rows = arcpy.UpdateCursor(r'c:/path/to/shp/update_geom.shp')
for row in rows:
  row = rows.next()
  pnt = arcpy.Point(row.getValue(shapeName).getPart(0).X + 0.5, row.getValue(shapeName).getPart(0).Y + 0.5)
  row.setValue(shapeName, pnt)
  rows.updateRow(row)
del rows

Best Answer

Related Solutions

[GIS] Updating Lat/Longs and actual position of point shapefile using arcpy.UpdateCursor()

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