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# scipy.special.gdtrib

`scipy.special.``gdtrib`(a, p, x, out=None) = <ufunc 'gdtrib'>

  Inverse of gdtr vs b.

  Returns the inverse with respect to the parameter b of `p = gdtr(a, b, x)`, the cumulative distribution function of the gamma distribution.

  Parameters: | a : array_like a parameter values of gdtr(a, b, x). 1/a is the “scale” parameter of the gamma distribution. p : array_like Probability values. x : array_like Nonnegative real values, from the domain of the gamma distribution. out : ndarray, 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: | b : ndarray Values of the b parameter such that p = gdtr(a, b, x). b is the “shape” parameter of the gamma distribution.

  See also

  `gdtr`
    CDF of the gamma distribution.
  `gdtria`
    Inverse with respect to a of gdtr(a, b, x).
  `gdtrix`
    Inverse with respect to x of gdtr(a, b, x).

  Examples

  First evaluate `gdtr`.

      >>> p = gdtr(1.2, 3.4, 5.6)
      >>> print(p)
      0.94378087442

  Verify the inverse.

      >>> gdtrib(1.2, p, 5.6)
      3.3999999999723882