`numpy:cumulative_sum`

source: /dev/numpy/build-install/usr/lib/python3.14/site-packages/numpy/_core/fromnumeric.py :2749

Signature

   def     cumulative_sum (    x    ,  / ,     axis    =  None   ,    dtype    =  None   ,    out    =  None   ,    include_initial    =  False     )

Summary

Return the cumulative sum of the elements along a given axis.

Extended Summary

This function is an Array API compatible alternative to numpy.cumsum.

Parameters

x : array_like: Input array.
axis : int, optional: Axis along which the cumulative sum is computed. The default (None) is only allowed for one-dimensional arrays. For arrays with more than one dimension axis is required.
dtype : dtype, optional: Type of the returned array and of the accumulator in which the elements are summed. If dtype is not specified, it defaults to the dtype of x, unless x has an integer dtype with a precision less than that of the default platform integer. In that case, the default platform integer is used.
out : ndarray, optional: Alternative output array in which to place the result. It must have the same shape and buffer length as the expected output but the type will be cast if necessary. See ufuncs-output-type for more details.
include_initial : bool, optional: Boolean indicating whether to include the initial value (zeros) as the first value in the output. With include_initial=True the shape of the output is different than the shape of the input. Default: False.

Returns

cumulative_sum_along_axis : ndarray: A new array holding the result is returned unless out is specified, in which case a reference to out is returned. The result has the same shape as x if include_initial=False.

Notes

Arithmetic is modular when using integer types, and no error is raised on overflow.

cumulative_sum(a)[-1] may not be equal to sum(a) for floating-point values since sum may use a pairwise summation routine, reducing the roundoff-error. See sum for more information.

Examples

a = np.array([1, 2, 3, 4, 5, 6])
a
np.cumulative_sum(a)

✓

np.cumulative_sum(a, dtype=float)  # specifies type of output value(s)

✗

b = np.array([[1, 2, 3], [4, 5, 6]])
np.cumulative_sum(b,axis=0)  # sum over rows for each of the 3 columns
np.cumulative_sum(b,axis=1)  # sum over columns for each of the 2 rows

✓

``cumulative_sum(c)[-1]`` may not be equal to ``sum(c)``

c = np.array([1, 2e-9, 3e-9] * 1000000)

✓

np.cumulative_sum(c)[-1]
c.sum()

✗

Aliases

numpy.cumulative_sum