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Diffstat (limited to 'doc/source/reference/arrays.ndarray.rst')
| -rw-r--r-- | doc/source/reference/arrays.ndarray.rst | 41 |
1 files changed, 38 insertions, 3 deletions
diff --git a/doc/source/reference/arrays.ndarray.rst b/doc/source/reference/arrays.ndarray.rst index 1bf7d1ac8..0cad2ac6e 100644 --- a/doc/source/reference/arrays.ndarray.rst +++ b/doc/source/reference/arrays.ndarray.rst @@ -120,6 +120,8 @@ strided scheme, and correspond to the strides: .. index:: single-segment, contiguous, non-contiguous +where :math:`d_j` = `self.itemsize * self.shape[j]`. + Both the C and Fortran orders are :term:`contiguous`, *i.e.,* :term:`single-segment`, memory layouts, in which every part of the memory block can be accessed by some combination of the indices. @@ -231,7 +233,7 @@ Array methods An :class:`ndarray` object has many methods which operate on or with the array in some fashion, typically returning an array result. These -methods are briefly explained below. (Each method's doc string has a +methods are briefly explained below. (Each method's docstring has a more complete description.) For the following methods there are also corresponding functions in @@ -317,11 +319,45 @@ Many of these methods take an argument named *axis*. In such cases, - If *axis* is *None* (the default), the array is treated as a 1-D array and the operation is performed over the entire array. This behavior is also the default if self is a 0-dimensional array or - array scalar. + array scalar. (An array scalar is an instance of the types/classes + float32, float64, etc., whereas a 0-dimensional array is an ndarray + instance containing precisely one array scalar.) - If *axis* is an integer, then the operation is done over the given axis (for each 1-D subarray that can be created along the given axis). +.. admonition:: Example of the *axis* argument + + A 3-dimensional array of size 3 x 3 x 3, summed over each of its + three axes + + >>> x + array([[[ 0, 1, 2], + [ 3, 4, 5], + [ 6, 7, 8]], + [[ 9, 10, 11], + [12, 13, 14], + [15, 16, 17]], + [[18, 19, 20], + [21, 22, 23], + [24, 25, 26]]]) + >>> x.sum(axis=0) + array([[27, 30, 33], + [36, 39, 42], + [45, 48, 51]]) + >>> # for sum, axis is the first keyword, so we may omit it, + >>> # specifying only its value + >>> x.sum(0), x.sum(1), x.sum(2) + (array([[27, 30, 33], + [36, 39, 42], + [45, 48, 51]]), + array([[ 9, 12, 15], + [36, 39, 42], + [63, 66, 69]]), + array([[ 3, 12, 21], + [30, 39, 48], + [57, 66, 75]])) + The parameter *dtype* specifies the data type over which a reduction operation (like summing) should take place. The default reduce data type is the same as the data type of *self*. To avoid overflow, it can @@ -333,7 +369,6 @@ argument must be an :class:`ndarray` and have the same number of elements. It can have a different data type in which case casting will be performed. - .. autosummary:: :toctree: generated/ |