This example illustrates the use of !NumPy's boolean indexing facilities to generate
an image of the [http://en.wikipedia.org/wiki/Mandelbrot_set Mandelbrot set].

{{{#!python
from numpy import *
import pylab

def mandelbrot( h,w, maxit=20 ):
	'''Returns an image of the Mandelbrot fractal of size (h,w).
	'''
	y,x = ogrid[ -1.4:1.4:h*1j, -2:0.8:w*1j ]
	c = x+y*1j
	z = c
	divtime = maxit + zeros(z.shape, dtype=int)

	for i in xrange(maxit):
		z  = z**2 + c
		diverge = z*conj(z) > 2**2            # who is diverging
		div_now = diverge & (divtime==maxit)  # who is diverging now
		divtime[div_now] = i                  # note when
		z[diverge] = 2                        # avoid diverging too much
	
	return divtime
	
pylab.imshow(mandelbrot(400,400))
pylab.show()
}}}

inline:mandelbrot.png