Well, after working on it on and off for the last week I finally managed to produce a working code. I think it's the most inelegant code ever written and it's extremely slow, but it works! Somewhere along the way I forgot I had set out to make it work within the ArcMAP environment so I ended up with a script that works on his own, albeit with cursor methods provided by arcgis scripting. It shouldn't be too hard to convert it to something that will work with calculate value but frankly, I'm done with it 😄
##This script calculates the n-th percentile of x number of point objects that fall within y number of polygon objects##
#workspace is the name of the root folder or gdb where the shape file or table can be found
workspace = "...."
#bestand is the name of the shape or table to be read
bestand = "...."
#the name of the field that contains the values for which you want to know the percentile
name = "...."
#A unique ID field that identifies the polygon object
id = "...."
P = 0.3 #P is the percentile
import math
import arcgisscripting
gp = arcgisscripting.create()
gp.Workspace = workspace
cur = gp.SearchCursor(bestand)
List = []
List2= []
row = cur.Next()
while row <> None:
List.append(row.name)
List2.append(row.id)
row = cur.next()
List3 = [None] * len(List) #This list is used to store the calculated percentiles later on
M = [List, List2, List3]
#The list is sorted by ID
indices = range(len(List))
indices.sort(key = M[1].__getitem__)
for i, sublist in enumerate(M):
M = [sublist for j in indices]
#Keeps track of the row numbers for wich the list jumps to the next unique ID
grens = []
grens.append(0)
p = 0
count = 0
while p<=48 and count<=(len(List)-2): #48 is a hardcoded number of unique polygon objects
#This block counts the number of instances of all unique polygon ID's.
temp = M[1][count]
while M[1][count]==temp:
if count == len(List)-1: break
else: count += 1
if count == len(List)-1: grens.append(count)
else: grens.append(count-1)
#Here a subpart of the list is sorted on ascending order of point object values
if count == len(List)-1: M[0][grens
+1:count+1]=sorted(M[0][grens
+1:count+1])
elif p == 0: M[0][grens
:count]=sorted(M[0][grens
:count])
else: M[0][grens
+1:count]=sorted(M[0][grens
+1:count])
#Excel method for calculating the percentile
#rank
if p == 0 or count == len(List)-1: n = P * (count-grens
-1)+1
else: n = P * (count-grens
-2)+1
if n == 1:
n = int(n)
N = M[0][n-1]
elif n == count-grens
:
N = M[0][count-grens
-1]
else:
rank = math.modf(n)
d = rank[0]
if p == 0: k = int(rank[1]) + grens
else: k = int(rank[1]) + grens
+ 1
N = M[0][k-1] + d * (M[0] - M[0][k-1])
#The calculated percentile is saved in the list
if p==0: k=grens
else: k=grens
+1
while k<=count:
M[2]=N
k += 1
p += 1
#The calculated percentiles should now be written to the file
i = 0
while i < len(List2):
where = "id=" + str(M[1])
cur = gp.UpdateCursor(bestand, where)
row = cur.Next()
while row:
row.SetValue("percentiel03", M[2]) #percentiel03 is the name of the new field
cur.UpdateRow(row)
row = cur.Next()
i += 1
Few notes:1: There is one hard coded value which is the number of unique polygon objects. This shouldn't be too hard to fix, but I have already spent too much time on this. 2: The writing process is painfully slow. It might be spead up by using the following piece of code instead:
j = 0
i = 0
while j <=len(grens)
while i < len(List2)
where = "id=" + str(M[1][grens+1])
cur = gp.UpdateCursor(bestand, where)
row = cur.Next()
while row:
row.SetValue("percentiel03", M[2]) #percentiel03 is the name of the new field
cur.UpdateRow(row)
row = cur.Next()
i += 1
j += 1
This is the more logical procedure as it skips to the next unique ID instead of going through the entire list. However I haven't tested thisFeel free to use, modify or discard the code. I am also very muc open to critique on my coding habits.Thanks for the help everyone.Regards,Hayvic
