scipy.special.ellipkm1

scipy.special.ellipkm1(p, out=None) = <ufunc 'ellipkm1'>

Complete elliptic integral of the first kind around m = 1

This function is defined as

\[K(p) = \int_0^{\pi/2} [1 - m \sin(t)^2]^{-1/2} dt\]

where m = 1 - p.

Parameters:

parray_like

Defines the parameter of the elliptic integral as m = 1 - p.

outndarray, optional

Optional output array for the function values

Returns:

Kscalar or ndarray

Value of the elliptic integral.

See also

ellipk

Complete elliptic integral of the first kind

ellipkinc

Incomplete elliptic integral of the first kind

ellipe

Complete elliptic integral of the second kind

ellipeinc

Incomplete elliptic integral of the second kind

elliprf

Completely-symmetric elliptic integral of the first kind.

Notes

Wrapper for the Cephes [1] routine ellpk.

For p <= 1, computation uses the approximation,

\[K(p) \approx P(p) - \log(p) Q(p)\]

where \(P\) and \(Q\) are tenth-order polynomials. The argument p is used internally rather than m so that the logarithmic singularity at m = 1 will be shifted to the origin; this preserves maximum accuracy. For p > 1, the identity

\[K(p) = K(1/p)/\sqrt{p}\]

is used.

ellipkm1 has experimental support for Python Array API Standard compatible backends in addition to NumPy. Please consider testing these features by setting an environment variable SCIPY_ARRAY_API=1 and providing CuPy, PyTorch, JAX, or Dask arrays as array arguments. The following combinations of backend and device (or other capability) are supported.

Library	CPU	GPU
NumPy	✅	n/a
CuPy	n/a	✅
PyTorch	✅	⛔
JAX	⚠️ no JIT	⛔
Dask	✅	n/a

See Support for the array API standard for more information.

References

[1]

Cephes Mathematical Functions Library, http://www.netlib.org/cephes/