scipy.special.cosm1#

scipy.special.cosm1(x, out=None) = <ufunc 'cosm1'>#

Compute cos(x) - 1, especially when x is near zero.

Parameters:

xarray_like: Real valued argument.
outndarray, optional: Optional output array for the function results.

Returns:

scalar or ndarray: Values of cos(x) - 1.

See also

expm1, log1p

Notes

Array API Standard Support

cosm1 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. cosm1 does not currently support out for the PyTorch backend.

See Support for the array API standard for more information.

Examples

>>> import numpy as np
>>> import scipy.special as sc

It is more accurate than computing cos(x) - 1 directly for x around 0.

>>> x = 1e-30
>>> np.cos(x) - 1
0.0
>>> sc.cosm1(x)
-5.0000000000000005e-61