scipy.special.poch#

scipy.special.poch(z, m, out=None) = <ufunc 'poch'>#

Pochhammer symbol.

The Pochhammer symbol (rising factorial) is defined as

\[(z)_m = \frac{\Gamma(z + m)}{\Gamma(z)}\]

For positive integer m it reads

\[(z)_m = z (z + 1) ... (z + m - 1)\]

See [DLMF] for more details.

Parameters:

z, marray_like: Real-valued arguments.
outndarray, optional: Optional output array for the function results

Returns:

scalar or ndarray: The value of the function.

Notes

Array API Standard Support

poch has support for Python Array API Standard compatible backends in addition to NumPy. The following combinations of backend and device (or other capability) are supported.

Library	CPU	GPU
NumPy	✅	n/a
CuPy	n/a	✅
PyTorch	✅	⛔
JAX	✅	✅
Dask	✅	n/a

For the NumPy backend, this function supports all NumPy ufunc keyword arguments. Other backends may support out, but none of the other ufunc kwargs. out is typically supported for CuPy and PyTorch, but not currently in cases where SciPy relies on a generic Array API implementation or, for PyTorch on CPU, falls back to the NumPy backend. out is never supported for JAX because JAX arrays are immutable. poch does not currently support out for the PyTorch backend.

See Support for the array API standard for more information.

References

[DLMF]

Nist, Digital Library of Mathematical Functions https://dlmf.nist.gov/5.2#iii

Examples

>>> import scipy.special as sc

It is 1 when m is 0.

>>> sc.poch([1, 2, 3, 4], 0)
array([1., 1., 1., 1.])

For z equal to 1 it reduces to the factorial function.

>>> sc.poch(1, 5)
120.0
>>> 1 * 2 * 3 * 4 * 5
120

It can be expressed in terms of the gamma function.

>>> z, m = 3.7, 2.1
>>> sc.poch(z, m)
20.529581933776953
>>> sc.gamma(z + m) / sc.gamma(z)
20.52958193377696