title: How to make grouper and axis the same length?
body: <p>For my assignment I'm supposed to plot the tracks of 20 hurricanes on a map using matplotlib. However when I run my code I get the error: <code>AssertionError:Grouper and axis must be the same length</code></p>
  
  <p>Here's the code I have:</p>
  
  <pre><code>import numpy as np
  from mpl_toolkits.basemap import Basemap
  import matplotlib.pyplot as plt 
  from PIL import *
  fig = plt.figure(figsize=(12,12))
  
  ax = fig.add_axes([0.1,0.1,0.8,0.8])
  
  m = Basemap(llcrnrlon=-100.,llcrnrlat=0.,urcrnrlon=-20.,urcrnrlat=57.,
          projection='lcc',lat_1=20.,lat_2=40.,lon_0=-60.,
          resolution ='l',area_thresh=1000.)
  
  m.bluemarble()
  m.drawcoastlines(linewidth=0.5)
  m.drawcountries(linewidth=0.5)
  m.drawstates(linewidth=0.5)
  
  # Creates parallels and meridians
  
  m.drawparallels(np.arange(10.,35.,5.),labels=[1,0,0,1])
  m.drawmeridians(np.arange(-120.,-80.,5.),labels=[1,0,0,1])
  m.drawmapboundary(fill_color='aqua')
  
  # Opens data file
  
  import pandas as pd
  name = [ ]
  df = pd.read_csv('louisianastormb.csv')
  for name, group in df.groupby([name]):
      latitude = group.lat.values
      longitude = group.lon.values
      x,y = m(longitude, latitude)
      plt.plot(x,y,'y-',linewidth=2 )
      plt.xlabel('Longitude')
      plt.ylabel('Latitude')
      plt.title('20 Hurricanes with Landfall in Louisiana')
  
  plt.savefig('20hurpaths.jpg', dpi=100)
  </code></pre>
  
  <p>Here's the full error output:</p>
  
  <pre><code> Traceback (most recent call last): 
  File "/home/darealmzd/lstorms.py", line 31, in &lt;module&gt; 
  for name, group in df.groupby([name]): 
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/generic.py", line 186, in groupby 
  squeeze=squeeze) 
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/groupby.py", line 533, in groupby 
  return klass(obj, by, **kwds) 
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/groupby.py", line 197, in __init__ 
  level=level, sort=sort) 
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/groupby.py", line 1325, in _get_grouper 
  ping = Grouping(group_axis, gpr, name=name, level=level, sort=sort) 
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/groupby.py", line 1129, in __init__ 
  self.grouper = _convert_grouper(index, grouper) 
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/groupby.py", line 1350, in _convert_grouper 
  raise Assertionerror('Grouper and axis must be same length') 
  Assertionerror: Grouper and axis must be same length 
  </code></pre>