erf, erfc
==============================================

Purpose
----------------

Computes the Gaussian error function (:func:`erf`) and its
complement (:func:`erfc`).

Format
----------------
.. function:: y = erf(x)
              y = erfc(x)

    :param x: The values used to compute the Gaussian error function or its complement.
    :type x: NxK matrix

    :return y: the Gaussian error function (:func:`erf`) or the complement of the Gaussian error function (:func:`erfc`).

    :rtype y: NxK matrix

Examples
----------------

::

    // Print 3 digits after the decimal point
    format /rd 5,3;

    // Assign x
    x = { .5 .4 .3,
          .6 .8 .3 };

    // Compute the Gaussian error function
    y = erf(x);

    /*
    ** Compute the complement of the
    ** Gaussian error function
    */
    yc = erfc(x);

After the above code:

::

    x = 0.500 0.400 0.300   y = 0.520 0.428 0.329   yc = 0.480 0.572 0.671
        0.600 0.800 0.300       0.604 0.742 0.329        0.396 0.258 0.671

Remarks
-------

The :func:`erf` and :func:`erfc` functions are closely related to the Normal distribution. Such that:

if :math:`x > 0`

::

      cdfn(x) = 0.5 * (1 + erf(x / sqrt(2));

and if :math:`x \leq 0`

::

      cdfn(x) = 0.5 * erfc(-x / sqrt(2));

.. seealso:: Functions :func:`cdfN`, :func:`cdfNc`