ローレンツのついでにgumowski

class Gumowski:
    "Gumowski-Mira Map"
    def __init__(self, x0, y0, a):
        self.x0 = x0; self.y0 = y0
        self.a  = a;

    def f(self,x):
        return self.a*x + 2*(1-self.a)*x**2/(1+x**2)

    def calc(self, n):
        dat = []
        x,y = self.x0, self.y0
        for i in range(n):
            nx = y  + self.f(x)
            ny = -x + self.f(nx)
            dat.append([nx,ny])
            x,y = nx,ny
        return dat

if __name__ == "__main__":
    from pylab import *
    from random import random
    n = 3
    for i in range(n*n):
        p = str(n) + str(n) + str(i+1)
        subplot(p)
        a = random() * 0.1 + 0.3
        gumow = Gumowski(20, 20, a)
        dat = gumow.calc(1000)
        x = [d[0] for d in dat]
        y = [d[1] for d in dat]
        plot(x,y,'bo', alpha=0.1,ms=5)

    savefig("gumow.png")