I need to write a function to calculate the distance between two cities.

import pandas as pd
from geopy import distance
capitals = pd.read_csv('https://raw.githubusercontent.com/j-rossi-nl/teaching-    data/main/2022_ITP/concap.csv')
capitals.head(5)
capitals.set_index('CapitalName', inplace = True)
capitals.loc["Amsterdam"]
def cities_distance(city_from: str, city_to: str = 'Amsterdam', cities: pd.DataFrame = capitals)->float:

I don't know how to select the capitallatitude and longitude when using geopy to calculate the distance. It needs to return the distance in kilometers.

CodePudding user response：

IIUC, you can use geopy.distance.geodesic. Below, a proposition based on your code :

import pandas as pd
from geopy.distance import geodesic

capitals = pd.read_csv("https://raw.githubusercontent.com/j-rossi-nl/teaching-data/main/2022_ITP/concap.csv",
                       index_col="CapitalName")

def cities_distance(city_from: str, city_to: str = "Amsterdam", cities: pd.DataFrame = capitals)->float:
    lat_long = ["CapitalLatitude", "CapitalLongitude"]

    origin = capitals.loc[city_from, lat_long].agg(tuple)
    destination = capitals.loc[city_to, lat_long].agg(tuple)

    return round(geodesic(origin,destination).km,2)

We use here pandas.DataFrame.loc with pandas.Series.agg to form a tuple with the coordinatees of the origin capital and pass it as a keyword argument to geodesic :

Parameters
point : (geopy.point.Point), list or tuple of (latitude, longitude), or string as "%(latitude)s, %(longitude)s".) – Starting point.

NB : The Geodesic distance will give a measure of the shortest path between the two capitals.

Output :

cities_distance("Hargeisa")
#5912.67

CodePudding user response：

In conjuntion with shapely.Geometry and pyproj.Geod

geometry_length Returns the geodesic length (meters) of the shapely geometry

from pyproj import Geod
from shapely.geometry import Point, LineString
import pandas as pd
capitals = pd.read_csv("https://raw.githubusercontent.com/j-rossi-nl/teaching-data/main/2022_ITP/concap.csv",
                       index_col="CapitalName")

line_string = LineString([Point(capitals['CapitalLongitude'].iloc[0], capitals['CapitalLatitude'].iloc[0]), Point(capitals['CapitalLongitude'].iloc[1], capitals['CapitalLatitude'].iloc[1])])
geod = Geod(ellps="WGS84")

print(f"{geod.geometry_length(line_string):.3f}")
#10255732.456

print(f"{geod.geometry_length(line_string)/1000:.3f}") # k/m
#10255.732