scipy.special.gdtria#
- scipy.special.gdtria(p, b, x, out=None) = <ufunc 'gdtria'>#
Inverse of
gdtr
vs a.Returns the inverse with respect to the parameter a of
p = gdtr(a, b, x)
, the cumulative distribution function of the gamma distribution.- Parameters:
- parray_like
Probability values.
- barray_like
b parameter values of gdtr(a, b, x). b is the “shape” parameter of the gamma distribution.
- xarray_like
Nonnegative real values, from the domain of the gamma distribution.
- outndarray, optional
If a fourth argument is given, it must be a numpy.ndarray whose size matches the broadcast result of a, b and x. out is then the array returned by the function.
- Returns:
- ascalar or ndarray
Values of the a parameter such that
p = gdtr(a, b, x)`. ``1/a
is the “scale” parameter of the gamma distribution.
See also
Notes
Wrapper for the CDFLIB [1] Fortran routine cdfgam.
The cumulative distribution function p is computed using a routine by DiDinato and Morris [2]. Computation of a involves a search for a value that produces the desired value of p. The search relies on the monotonicity of p with a.
References
[1]Barry Brown, James Lovato, and Kathy Russell, CDFLIB: Library of Fortran Routines for Cumulative Distribution Functions, Inverses, and Other Parameters.
[2]DiDinato, A. R. and Morris, A. H., Computation of the incomplete gamma function ratios and their inverse. ACM Trans. Math. Softw. 12 (1986), 377-393.
Examples
First evaluate
gdtr
.>>> from scipy.special import gdtr, gdtria >>> p = gdtr(1.2, 3.4, 5.6) >>> print(p) 0.94378087442
Verify the inverse.
>>> gdtria(p, 3.4, 5.6) 1.2