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#!/usr/bin/env python
"""
Demonstration of the quiver command in combination with other plotting
commands.
"""
from scitools.std import *
setp(interactive=False)
xv, yv = ndgrid(linspace(-5,5,81), linspace(-5,5,81))
values = sin(sqrt(xv**2 + yv**2))
pcolor(xv, yv, values, shading='interp')
# create a coarser grid for the gradient field:
xv, yv = ndgrid(linspace(-5,5,21), linspace(-5,5,21), sparse=True)
values = sin(sqrt(xv**2 + yv**2))
# compute the gradient field:
uu, vv = gradient(values)
hold('on')
quiver(xv, yv, uu, vv, 'filled', 'k', axis=[-6,6,-6,6])
show()
#hardcopy('quiver2a.eps')
#hardcopy('quiver2a.png')
figure()
contour(xv, yv, values, 15, hold=True)
quiver(xv, yv, uu, vv, axis=[-6,6,-6,6])
show()
#hardcopy('quiver2b.eps')
#hardcopy('quiver2b.png')
raw_input("Press Return key to quit: ")
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