title: Vectorised Haversine formula with a pandas dataframe
body: <p>I know that to find the distance between two latitude, longitude points I need to use the haversine function:</p>
  
  <pre><code>def haversine(lon1, lat1, lon2, lat2):
      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 * asin(sqrt(a)) 
      km = 6367 * c
      return km
  </code></pre>
  
  <p>I have a DataFrame where one column is latitude and another column is longitude. I want to find out how far these points are from a set point, -56.7213600, 37.2175900. How do I take the values from the DataFrame and put them into the function? </p>
  
  <p>example DataFrame:</p>
  
  <pre><code>     SEAZ     LAT          LON
  1    296.40,  58.7312210,  28.3774110  
  2    274.72,  56.8148320,  31.2923240
  3    192.25,  52.0649880,  35.8018640
  4     34.34,  68.8188750,  67.1933670
  5    271.05,  56.6699880,  31.6880620
  6    131.88,  48.5546220,  49.7827730
  7    350.71,  64.7742720,  31.3953780
  8    214.44,  53.5192920,  33.8458560
  9      1.46,  67.9433740,  38.4842520
  10   273.55,  53.3437310,   4.4716664
  </code></pre>