diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/source/user/how-to-index.rst | 2 | ||||
| -rw-r--r-- | doc/source/user/how-to-partition.rst | 42 |
2 files changed, 21 insertions, 23 deletions
diff --git a/doc/source/user/how-to-index.rst b/doc/source/user/how-to-index.rst index 41061d5f4..e47e9a204 100644 --- a/doc/source/user/how-to-index.rst +++ b/doc/source/user/how-to-index.rst @@ -1,6 +1,6 @@ .. currentmodule:: numpy -.. _how-to-index.rst: +.. _how-to-index: ***************************************** How to index :class:`ndarrays <.ndarray>` diff --git a/doc/source/user/how-to-partition.rst b/doc/source/user/how-to-partition.rst index b5dd3f01f..224519364 100644 --- a/doc/source/user/how-to-partition.rst +++ b/doc/source/user/how-to-partition.rst @@ -1,8 +1,8 @@ .. _how-to-partition: -===================================== -How to partition a domain using NumPy -===================================== +================================================= +How to create arrays with regularly-spaced values +================================================= There are a few NumPy functions that are similar in application, but which provide slightly different results, which may cause confusion if one is not sure @@ -30,7 +30,7 @@ Both `numpy.linspace` and `numpy.arange` provide ways to partition an interval depending on the chosen starting and ending points, and the **step** (the length of the subintervals). -* Use `numpy.arange` if you want integer steps. +* **Use** `numpy.arange` **if you want integer steps.** `numpy.arange` relies on step size to determine how many elements are in the returned array, which excludes the endpoint. This is determined through the @@ -42,10 +42,14 @@ of the subintervals). array([0, 2, 4, 6, 8]) The arguments ``start`` and ``stop`` should be integer or real, but not - complex numbers. + complex numbers. `numpy.arange` is similar to the Python built-in + :py:class:`range`. -* Use `numpy.linspace` if you want the endpoint to be included in the result, or - if you are using a non-integer step size. + Floating-point inaccuracies can make ``arange`` results with floating-point + numbers confusing. In this case, you should use `numpy.linspace` instead. + +* **Use** `numpy.linspace` **if you want the endpoint to be included in the + result, or if you are using a non-integer step size.** `numpy.linspace` *can* include the endpoint and determines step size from the `num` argument, which specifies the number of elements in the returned @@ -154,20 +158,14 @@ of ``start``) and ends with ``base ** stop``:: nD domains ========== -nD domains can be partitioned into *grids*. - - Two instances of `nd_grid` are made available in the NumPy namespace, - `mgrid` and `ogrid`, approximately defined as:: - - mgrid = nd_grid(sparse=False) - ogrid = nd_grid(sparse=True) - xs, ys = np.meshgrid(x, y, sparse=True) +nD domains can be partitioned into *grids*. This can be done using one of the +following functions. ``meshgrid`` ------------ -The purpose of ``numpy.meshgrid`` is to create a rectangular grid out of a set of -one-dimensional coordinate arrays. +The purpose of ``numpy.meshgrid`` is to create a rectangular grid out of a set +of one-dimensional coordinate arrays. Given arrays @@ -208,8 +206,7 @@ the coordinate pairs determining this grid. --------- ``numpy.mgrid`` can be used as a shortcut for creating meshgrids. It is not a -function, but a ``nd_grid`` instance that, when indexed, returns a -multidimensional meshgrid. +function, but when indexed, returns a multidimensional meshgrid. :: @@ -239,9 +236,10 @@ multidimensional meshgrid. ``ogrid`` --------- -Similar to ``numpy.mgrid``, ``numpy.ogrid`` returns a ``nd_grid`` instance, but -the result is an *open* multidimensional meshgrid. This means that when it is -indexed, so that only one dimension of each returned array is greater than 1. +Similar to ``numpy.mgrid``, ``numpy.ogrid`` returns an *open* multidimensional +meshgrid. This means that when it is indexed, only one dimension of each +returned array is greater than 1. This avoids repeating the data and thus saves +memory, which is often desirable. These sparse coordinate grids are intended to be use with :ref:`broadcasting`. When all coordinates are used in an expression, broadcasting still leads to a |