http://hg.python.org/cpython/rev/69c91ee0b7dd changeset: 69088:69c91ee0b7dd branch: 3.2 parent: 69077:a00b9a5688da user: Raymond Hettinger <python@rcn.com> date: Thu Mar 31 12:04:53 2011 -0700 summary: Add links to make the math docs more usable. files: Doc/library/math.rst | 30 +++++++++++++++++++++++------- 1 files changed, 23 insertions(+), 7 deletions(-) diff --git a/Doc/library/math.rst b/Doc/library/math.rst --- a/Doc/library/math.rst +++ b/Doc/library/math.rst @@ -156,10 +156,10 @@ .. function:: expm1(x) - Return ``e**x - 1``. For small floats *x*, the subtraction in - ``exp(x) - 1`` can result in a significant loss of precision; the - :func:`expm1` function provides a way to compute this quantity to - full precision:: + Return ``e**x - 1``. For small floats *x*, the subtraction in ``exp(x) - 1`` + can result in a `significant loss of precision + <http://en.wikipedia.org/wiki/Loss_of_significance>`_\; the :func:`expm1` + function provides a way to compute this quantity to full precision:: >>> from math import exp, expm1 >>> exp(1e-5) - 1 # gives result accurate to 11 places @@ -269,6 +269,9 @@ Hyperbolic functions -------------------- +`Hyperbolic functions <http://en.wikipedia.org/wiki/Hyperbolic_function>`_ +are analogs of trigonometric functions that are based on hyperbolas +instead of circles. .. function:: acosh(x) @@ -305,21 +308,34 @@ .. function:: erf(x) - Return the error function at *x*. + Return the `error function <http://en.wikipedia.org/wiki/Error_function>`_ at + *x*. + + The :func:`erf` function can be used to compute traditional statistical + functions such as the `cumulative standard normal distribution + <http://en.wikipedia.org/wiki/Normal_distribution#Cumulative_distribution_function>`_:: + + def phi(x): + 'Cumulative distribution function for the standard normal distribution' + return (1.0 + erf(x / sqrt(2.0))) / 2.0 .. versionadded:: 3.2 .. function:: erfc(x) - Return the complementary error function at *x*. + Return the complementary error function at *x*. The `complementary error + function <http://en.wikipedia.org/wiki/Error_function>`_ is defined as + ``1.0 - erf(x)``. It is used for large values of *x* where a straight + substraction from *1* would cause a `loss of significance + <http://en.wikipedia.org/wiki/Loss_of_significance>`_\. .. versionadded:: 3.2 .. function:: gamma(x) - Return the Gamma function at *x*. + Return the `Gamma function<http://en.wikipedia.org/wiki/Gamma_function>` at *x*. .. versionadded:: 3.2 -- Repository URL: http://hg.python.org/cpython