Function indices

numpy/_core/numeric.py:1726–1824

Return an array representing the indices of a grid. Compute an array where the subarrays contain index values 0, 1, ... varying only along the corresponding axis. Parameters ---------- dimensions : sequence of ints The shape of the grid. dtype : dtype, optional

(dimensions, dtype=int, sparse=False)

@set_module('numpy')
def indices(dimensions, dtype=int, sparse=False):
    """
    Return an array representing the indices of a grid.

    Compute an array where the subarrays contain index values 0, 1, ...
    varying only along the corresponding axis.

    Parameters
    ----------
    dimensions : sequence of ints
        The shape of the grid.
    dtype : dtype, optional
        Data type of the result.
    sparse : boolean, optional
        Return a sparse representation of the grid instead of a dense
        representation. Default is False.

    Returns
    -------
    grid : one ndarray or tuple of ndarrays
        If sparse is False:
            Returns one array of grid indices,
            ``grid.shape = (len(dimensions),) + tuple(dimensions)``.
        If sparse is True:
            Returns a tuple of arrays, with
            ``grid[i].shape = (1, ..., 1, dimensions[i], 1, ..., 1)`` with
            dimensions[i] in the ith place

    See Also
    --------
    mgrid, ogrid, meshgrid

    Notes
    -----
    The output shape in the dense case is obtained by prepending the number
    of dimensions in front of the tuple of dimensions, i.e. if `dimensions`
    is a tuple ``(r0, ..., rN-1)`` of length ``N``, the output shape is
    ``(N, r0, ..., rN-1)``.

    The subarrays ``grid[k]`` contains the N-D array of indices along the
    ``k-th`` axis. Explicitly::

        grid[k, i0, i1, ..., iN-1] = ik

    Examples
    --------
    >>> import numpy as np
    >>> grid = np.indices((2, 3))
    >>> grid.shape
    (2, 2, 3)
    >>> grid[0]        # row indices
    array([[0, 0, 0],
           [1, 1, 1]])
    >>> grid[1]        # column indices
    array([[0, 1, 2],
           [0, 1, 2]])

    The indices can be used as an index into an array.