Module « numpy.random »

Fonction standard_cauchy - module numpy.random

Signature de la fonction standard_cauchy

Description

standard_cauchy.__doc__

        standard_cauchy(size=None)

        Draw samples from a standard Cauchy distribution with mode = 0.

        Also known as the Lorentz distribution.

        .. note::
            New code should use the ``standard_cauchy`` method of a ``default_rng()``
            instance instead; please see the :ref:`random-quick-start`.

        Parameters
        ----------
        size : int or tuple of ints, optional
            Output shape.  If the given shape is, e.g., ``(m, n, k)``, then
            ``m * n * k`` samples are drawn.  Default is None, in which case a
            single value is returned.

        Returns
        -------
        samples : ndarray or scalar
            The drawn samples.

        See Also
        --------
        Generator.standard_cauchy: which should be used for new code.

        Notes
        -----
        The probability density function for the full Cauchy distribution is

        .. math:: P(x; x_0, \gamma) = \frac{1}{\pi \gamma \bigl[ 1+
                  (\frac{x-x_0}{\gamma})^2 \bigr] }

        and the Standard Cauchy distribution just sets :math:`x_0=0` and
        :math:`\gamma=1`

        The Cauchy distribution arises in the solution to the driven harmonic
        oscillator problem, and also describes spectral line broadening. It
        also describes the distribution of values at which a line tilted at
        a random angle will cut the x axis.

        When studying hypothesis tests that assume normality, seeing how the
        tests perform on data from a Cauchy distribution is a good indicator of
        their sensitivity to a heavy-tailed distribution, since the Cauchy looks
        very much like a Gaussian distribution, but with heavier tails.

        References
        ----------
        .. [1] NIST/SEMATECH e-Handbook of Statistical Methods, "Cauchy
              Distribution",
              https://www.itl.nist.gov/div898/handbook/eda/section3/eda3663.htm
        .. [2] Weisstein, Eric W. "Cauchy Distribution." From MathWorld--A
              Wolfram Web Resource.
              http://mathworld.wolfram.com/CauchyDistribution.html
        .. [3] Wikipedia, "Cauchy distribution"
              https://en.wikipedia.org/wiki/Cauchy_distribution

        Examples
        --------
        Draw samples and plot the distribution:

        >>> import matplotlib.pyplot as plt
        >>> s = np.random.standard_cauchy(1000000)
        >>> s = s[(s>-25) & (s<25)]  # truncate distribution so it plots well
        >>> plt.hist(s, bins=100)
        >>> plt.show()