Close Does Not Work

I use x.close to clear. It closes the canvas but the image is still there when I plot the second image.

import vcs, cdms2, time, datetime
# Open data file:

cdmsfile = cdms2.open( 'clt.nc' )
# Extract a 3 dimensional data set

data = cdmsfile('clt')

x=vcs.init()
p=x.plot(data)
x.close()
x.plot(data[4][1:89])
