Amy Rose - 9 months ago 57

Python Question

I have a dataframe called lat_long which contains the latitude and longitude of some locations. I want to find the difference between each following location. When I use the example haversine function, i get an error. KeyError: ('1', u'occurred at index 0').

`1 2`

0 -6.081689 145.391881

1 -5.207083 145.788700

2 -5.826789 144.295861

3 -6.569828 146.726242

4 -9.443383 147.220050

def haversine(row):

lon1 = lat_long['1']

lat1 = lat_long['2']

lon2 = row['1']

lat2 = row['2']

lon1, lat1, lon2, lat2 = map(radians, [lon1, lat1, lon2, lat2])

dlon = lon2 - lon1

dlat = lat2 - lat1

a = sin(dlat/2)**2 + cos(lat1) * cos(lat2) * sin(dlon/2)**2

c = 2 * arcsin(sqrt(a))

km = 6367 * c

return km

lat_long['distance'] = lat_long.apply(lambda row: haversine(row), axis=1)

lat_long

Answer Source

Try this solution:

```
def haversine_np(lon1, lat1, lon2, lat2):
"""
Calculate the great circle distance between two points
on the earth (specified in decimal degrees)
All args must be of equal length.
"""
lon1, lat1, lon2, lat2 = map(np.radians, [lon1, lat1, lon2, lat2])
dlon = lon2 - lon1
dlat = lat2 - lat1
a = np.sin(dlat/2.0)**2 + np.cos(lat1) * np.cos(lat2) * np.sin(dlon/2.0)**2
c = 2 * np.arcsin(np.sqrt(a))
km = 6367 * c
return km
```

Demo:

```
In [17]: df
Out[17]:
lat lon
0 -6.081689 145.391881
1 -5.207083 145.788700
2 -5.826789 144.295861
3 -6.569828 146.726242
4 -9.443383 147.220050
In [18]: df['dist'] = \
...: haversine_np(df.lon.shift(), df.lat.shift(), df.ix[1:, 'lon'], df.ix[1:, 'lat'])
In [19]: df
Out[19]:
lat lon dist
0 -6.081689 145.391881 NaN
1 -5.207083 145.788700 106.638117
2 -5.826789 144.295861 178.907364
3 -6.569828 146.726242 280.904983
4 -9.443383 147.220050 323.913612
```