title: Python : setting colour limits for basemap's pcolormesh
body: <p>Python newbie here. I'm trying to set the colour limits in a basemap pcolormesh, in the same way that</p>
  
  <pre><code>matplotlib.pyplot.clim(-1, 1)
  </code></pre>
  
  <p>would set the colour minimum to -1 and maximum to 1. My code looks like this:</p>
  
  <pre><code>llcrnrlat = numpy.amin(gridLatLon['lat'])-0.5
  urcrnrlat = numpy.amax(gridLatLon['lat'])+0.5
  llcrnrlon = numpy.amin(gridLatLon['lon'])-0.5
  urcrnrlon = numpy.amax(gridLatLon['lon'])+0.5
  
  m = Basemap(projection='cyl', llcrnrlat=llcrnrlat,urcrnrlat=urcrnrlat,\
          llcrnrlon=llcrnrlon,urcrnrlon=urcrnrlon,resolution='c')
  
  y, x = m(gridLatLon['lat'], gridLatLon['lon'])
  
  m.drawcoastlines()
  m.drawcountries()
  m.pcolormesh(x, y, efdata, latlon=True)
  </code></pre>
  
  <p>and it produces <a href="https://i.stack.imgur.com/qZUb7.png" rel="nofollow noreferrer">this</a>, whereas I'm looking for the colours to be between -1 and 1, which would produce something like <a href="https://i.stack.imgur.com/Q8DgK.png" rel="nofollow noreferrer">this</a> (which I did using clim() but isn't on basemap).</p>
  
  <p>Any and all suggestions as to how to improve my code are welcome.</p>
  
  <p>Edit : <code>gridLatLon</code> is a dictionary containing one field called <code>lat</code>, which is a 2D numpy array of latitudes, and one field called <code>lon</code>, a 2D numpy array of corresponding longitudes. I'm trying to plot <code>efdata</code>, another 2D numpy array of the same size as the others.</p>