from pylab import *
from matplotlib.toolkits.basemap import Basemap,shiftgrid


def contour(lon,lat,x):
    """
    Makes a contour map of field x, with coastlines overlayed
    lon is 1-d array of longitudes in INCREASING order
    lat is 1-d array of latitudes in INCREASING order
    x is a 2-d array of data to plot, arranged as
                     lat  lon
                  x[  :  , :  ] 
                    
    """
    map = Basemap(projection='cyl',
                  llcrnrlon=lon[0],
                  urcrnrlon=lon[-1],
                  llcrnrlat=lat[0],
                  urcrnrlat=lat[-1],
                  resolution='c')
    Lon, Lat = map(*meshgrid(lon,lat))
    map.contourf(Lon,Lat,x)
    map.drawcoastlines() # draw coastlines
    map.drawmapboundary() # draw a line around the map region
    map.drawparallels(arange(-90.,90.,10.)) # draw parallels
    map.drawmeridians(arange(-360.,360.,10.)) # draw meridians
    colorbar(orientation='horizontal') # draw colorbar