`scipy.stats._continuous_distns:gamma_gen`

Signature

class gamma_gen(momtype = 1, a = None, b = None, xtol = 1e-14, badvalue = None, name = None, longname = None, shapes = None, seed = None)

A gamma continuous random variable.

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The probability density function for gamma is:

f (x, a) = \frac{x ^{a - 1} e ^{- x}}{Γ ( a )}

for $x \geq 0$ , $a > 0$ . Here $Γ (a)$ refers to the gamma function.

gamma takes a as a shape parameter for $a$ .

When $a$ is an integer, gamma reduces to the Erlang distribution, and when $a = 1$ to the exponential distribution.

Gamma distributions are sometimes parameterized with two variables, with a probability density function of:

f (x, α, β) = \frac{β ^{α} x ^{α - 1} e ^{- β x}}{Γ ( α )}

Note that this parameterization is equivalent to the above, with scale = 1 / beta.

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