Chris Beaumont's IDL Library

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result = lognormal_cdf(x, a, sigma [, param=param])

Evaluate the cumulative distribution function of a lognormal distribution.

The lognormal distribution PDF is defined as P(x) = [sqrt(2 * pi) * sigma * x]^(-1) * exp[ -ln(x / a)^2 / (2 * sigma)^2]

Return value



x in required

The abcissa values at which to compute the CDF

a in required

The median of the distribution (see formula above)

sigma in required

The width of the distribution (see formula above)


param in optional

An optional 2-element array, listing [a, sigma]. This is provided for convenience, as some functions (e.g., ksone in the IDL Astronomy user's library) prefer to pass parameters this way.

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Modifcation date: Mon Aug 1 21:29:47 2011
Lines: 47