Find Minimum for element in multiple dimensional array

Robert Davis rdavis7408 at gmail.com
Thu Jul 23 00:54:06 CEST 2015


Given a set of arrays within an array how do I find the arrays with the minimum values based on two elements/columns in the array? Those two elements/columns are the destination zip code and distance.

I have an array of arrays that have a origin zip code, origin latitude, origin longitude, destination zip code, destination latitude, destination longitude, and miles between the two points.

I need to keep only those combinations that represent the minimum mileage between to the destination zip code. For example a point in New Jersey may have a distance from the Philadelphia Office that is 45 miles, from the Newark Office that is 78 miles and one from the Delaware Office that is 58 miles.

I need to keep the mileage from the Philadelphia Office that is 45 miles and produce a .csv file that has origin zip code, origin latitude, origin longitude, destination zip code, destination latitude, destination longitude, and miles between the two points.

The array looks like this:

[['37015', 'TN31', 36.2777, -87.0046, 'NY', 'White Plains', '10629', 41.119008, -73.732996, 77.338920003], 
['72202', 'ARB1', 34.739224, -92.27765, 'NY', 'White Plains', '10629', 41.119008, -73.732996, 1099.7837975322097]]

My code looks like this :

import csv
import math


def calculate_distance(lat1, lon1, lat2, lon2):

    if (not lat1) or (not lon1) or (not lat2) or (not lon2):
            return -1

    lat1 = float(lat1) * math.pi/180
    lon1 = float(lon1) * math.pi/180
    lat2 = float(lat2) * math.pi/180
    lon2 = float(lon2) * math.pi/180

    return 3959.0 * math.acos(math.sin(lat1) * math.sin(lat2) +   math.cos(lat1) * math.cos(lat2) * math.cos(lon2-lon1))

#Above function changed from the following URL: http://iamtgc.com/geocoding- with-python/


InputPath = "C:\\Users\\jacobs\\Downloads\\ZipCodes\\"

ZipCodes = "zipcode.csv"
RptgOfficeFile = "Reporting_Office_2015072001.csv"
InputFile = InputPath+RptgOfficeFile
zInputFile = InputPath+ZipCodes
zOutputFile = InputPath+'Zip_Code_Distance.csv'
z1OutputFile = InputPath+'Minimum_Distance_Zip_Code_File.csv'


f = open(InputFile, 'r')

zO = open(zOutputFile,'w')
z1 = open(z1OutputFile,'w')

lines = [ ]
OfficeZipcodes = []
ZipRptOffice = {}
OLatitude = [ ]
OLongitude = [ ]
OLocationCode = []
dzip = []
dLatitude = []
dLongitude = []
dCity = []
dState = []
Combined =[]
Answers = []

for line in f:
  l = [i.strip() for i in line.split(',')]
  OfficeZipcodes.append(l[4])
  ZipRptOffice[l[4]]= l[3]
  OLatitude.append(l[5])
  OLongitude.append(l[6])
  OLocationCode.append(l[3])

del OfficeZipcodes[0]
del OLatitude[0] 
del OLongitude[0]
del OLocationCode[0]


zf = csv.DictReader(open(zInputFile))
#http://courses.cs.washington.edu/courses/cse140/13wi/csv-parsing.html

for row in zf:
    dzip.append(row["zip"])
    dLatitude.append(float(row["latitude"]))
    dLongitude.append(float(row["longitude"]))
    dCity.append(row["city"])
    dState.append(row["state"])


for i in range(len(OfficeZipcodes)):
    for j in range(len(dzip)):
        Distance = calculate_distance(OLatitude[i], OLongitude[i],dLatitude[j],dLongitude[j])
        Combined.append([OfficeZipcodes[i], OLocationCode[i],float(OLatitude[i]),float(OLongitude[i]),dState[j],dCity[j],dzip[j], dLatitude[j],dLongitude[j],Distance])
for i in range(len(Combined)):
  zO.write(str(Combined[i][0])+","+str(Combined[i][1])+","+str(Combined[i][2])+","+ str(Combined[i][3])+","+str(Combined[i][4])+","+ str(Combined[i][5])+","+ str(Combined[i][6])+","+str(Combined[i][7])+","+ str(Combined[i][8])+","+str(Combined[i][9])+"\n")

zO.close()
f.close()

I am using Python 2.7 on a Windows 7 machine.

Please help me get my head around how to accomplish this task.

Thank you very much.

Robert Davis


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