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scipy tutorial - Baustatik-Info-Server

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SciPy Reference Guide, Release 0.8.dev<br />

Examples<br />

loc : array-like, optional<br />

location parameter (default=0)<br />

scale : array-like, optional<br />

scale parameter (default=1)<br />

size : int or tuple of ints, optional<br />

shape of random variates (default computed from input arguments )<br />

moments : string, optional<br />

composed of letters [’mvsk’] specifying which moments to compute where ‘m’<br />

= mean, ‘v’ = variance, ‘s’ = (Fisher’s) skew and ‘k’ = (Fisher’s) kurtosis. (default=’mv’)<br />

>>> import matplotlib.pyplot as plt<br />

>>> numargs = johnsonsu.numargs<br />

>>> [ a,b ] = [0.9,]*numargs<br />

>>> rv = johnsonsu(a,b)<br />

Display frozen pdf<br />

>>> x = np.linspace(0,np.minimum(rv.dist.b,3))<br />

>>> h=plt.plot(x,rv.pdf(x))<br />

Check accuracy of cdf and ppf<br />

>>> prb = johnsonsu.cdf(x,a,b)<br />

>>> h=plt.semilogy(np.abs(x-johnsonsu.ppf(prb,a,b))+1e-20)<br />

Random number generation<br />

>>> R = johnsonsu.rvs(a,b,size=100)<br />

Johnson SU distribution<br />

johnsonsu.pdf(x,a,b) = b/sqrt(x**2+1) * phi(a + b*log(x+sqrt(x**2+1))) for all x, a,b > 0, and phi is the normal<br />

pdf.<br />

542 Chapter 3. Reference

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