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08.18.2008 at 09:44PM PDT, ID: 23658538
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8.0

Python script - add stack

Asked by mgjust in Python Scripting Language, GIS & GPS Programming

Hello,
I was seeking help on a GIS forum on the get following response:

---
Below is the algorithm. It begins with a stack P of your 412 points in priority order and an empty stack S. When it ends, S contains the points to select. You can obtain your areas by buffering S.

When all 412 points are in a single layer, a straightforward modification of an ArcTool like NearestNeighbor.py will do this algorithm for you: just remove the unnecessary parts and replace the inner loop body with the code needed to implement the two inner lines of this algorithm. Output the stack S (which in Python will be implemented as a dictionary of points).
        

Begin
  d = 2*5
  While P is not empty {
    a = Pop(P)
    x = d+1
    For each point b in S {
      x = Min(x, Distance(a,b))
      If (x < d) then break
    }
   If (x >= d) then push a on S
  }
End

---

Below is the nearestneighbor code the author suggested to modify. Does anyone have any suggestions on how to implement this (i.e. combine these two codes)? Whats a stack?

Thanks,
MJStart Free Trial 
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# Analyze crime data to determine if spatial patterns are statistically significant
 
# Import system modules
import arcgisscripting
 
# Create the Geoprocessor object
gp = arcgisscripting.create()
 
# Local variables...
workspace = "C:/project93/data"
crime_data = "burglaries.shp"
 
try:
    # Set the current workspace (to avoid having to specify the full path to the feature classes each time)
    gp.workspace = workspace
 
    # Obtain Nearest Neighbor Ratio and Z Score
    # Process: Average Nearest Neighbor...
    nn_output = gp.AverageNearestNeighbor_stats(crime_data, "Euclidean Distance", "false", "#")
    nn_values = nn_output.split(";")
    print "The nearest neighbor index is: " + nn_values[0]
    print "The z score of the nearest neighbor index is: " + nn_values[1]
 
except:
    # If an error occurred when running the tool, print out the error message.
    print gp.GetMessages()
[+][-]08.19.2008 at 05:23AM PDT, ID: 22259083

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[+][-]08.19.2008 at 05:25AM PDT, ID: 22259096

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Solution Provided By: ramrom
Participating Experts: 1
Solution Grade: B
 
 
[+][-]08.19.2008 at 10:31AM PDT, ID: 22261927

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