There was a median calculation tool posted here somewhere by Caleb Mackey.
But no joy with search. So here it is again.
'''
Written By Caleb Mackey
4/17/2013
Calculates Median Statistics
'''
import arcpy, os, sys, traceback
# env settings
arcpy.env.overwriteOutput = True
arcpy.env.qualifiedFieldNames = False
def GetMedian(in_list):
sorted_list = sorted(in_list)
median = int(round(len(sorted_list) / 2))
if len(sorted_list)%2==0:
med_val = float(sorted_list[median-1]
+ sorted_list[median]) / 2
else:
med_val = sorted_list[median]
return med_val
def GetMedianValues(source_fc, new_table, case_field, value_field):
''' Generates a table with Median Values, summarized by case_field. If the
goal is to get the median for the entire table, use a case field that has
the same value for all records.
source_fc - input feature class to compute median statistics for
new_table - output table
case_field - similar to dissolve field, computes stats based on unique values in this field
value_field - field that contains the actual values for statistics; must be numeric
'''
# Get unique value list for query
print 'starting cursor'
with arcpy.da.SearchCursor(source_fc, [case_field]) as rows:
un_vals = list(set(r[0] for r in rows))
lyr = arcpy.MakeFeatureLayer_management(source_fc,'source_layer')
values = {}
# Get Median UseValue for each station name
for st in un_vals:
query = '"{0}" = \'{1}\''.format(case_field, st)
arcpy.SelectLayerByAttribute_management(lyr, 'NEW_SELECTION', query)
use_vals = []
with arcpy.da.SearchCursor(lyr, [value_field]) as rows:
for row in rows:
if row[0] != None:
use_vals.append(row[0])
if len(use_vals) > 0:
median = GetMedian(use_vals)
values[st] = [median, len(use_vals)]
# Create new Summary Statistics table with median
#
if arcpy.Exists(new_table):
arcpy.Delete_management(new_table)
arcpy.CreateTable_management(os.path.split(new_table)[0],os.path.basename(new_table))
# Get field names and types
for field in arcpy.ListFields(source_fc):
if field.name in [case_field, value_field]:
ftype = field.type
name = field.name
length = field.length
pres = field.precision
scale = field.scale
if name == value_field:
if new_table.endswith('.dbf'):
name = 'MED_' + value_field[:6]
else:
name = 'MED_' + value_field
value_field2 = name
arcpy.AddField_management(new_table,name,ftype,pres,scale,length)
# Add frequency field
arcpy.AddField_management(new_table,'FREQUENCY','LONG')
# Insert rows
with arcpy.da.InsertCursor(new_table, [case_field, value_field2, 'FREQUENCY']) as rows:
for k,v in sorted(values.iteritems()):
rows.insertRow((k, v[0], v[1]))
# report results
print 'Created %s' %os.path.basename(new_table)
arcpy.AddMessage('Created %s' %os.path.basename(new_table))
# .dbf's are automatically given a 'Field1' field...Clean this up
try:
if new_table.endswith('.dbf'):
arcpy.DeleteField_management(new_table, 'Field1')
except:
pass
print 'Done'
if __name__ == '__main__':
## # testing
## source_fc = r'C:\Testing\Test.gdb\CSR_by_TWP'
#### new_table = r'C:\Testing\Test.gdb\Median_CSR' #gdb test
## new_table = r'C:\Testing\Median_CSR.dbf' #dbf test
## case_field = 'NAME'
## value_field = 'AVE_CSR'
# Script tool params
source_fc = arcpy.GetParameterAsText(0)
new_table = arcpy.GetParameterAsText(1)
case_field = arcpy.GetParameterAsText(2)
value_field = arcpy.GetParameterAsText(3)
GetMedianValues(source_fc, new_table, case_field, value_field)
