ellippy.bulirsch.cel#
- ellippy.bulirsch.cel(kc, p, a, b)[source]#
Computes general complete elliptic integral in Bulirsch form
cel.\[\mathrm{cel}(k_c, p, a, b) = \int_0^{\pi/2} \frac{a\cos^2\theta + b\sin^2\theta}{(\cos^2\theta + p\sin^2\theta)\,\sqrt{\cos^2\theta + k_c^2\sin^2\theta}}\,\mathrm{d}\theta\]- Parameters:
kc (
ArrayLike) – Complementary modulus. kc ∈ ℝ, kc ≠ 0.p (
ArrayLike) – Characteristic parameter. p ∈ ℝ, p ≠ 0.a (
ArrayLike) – Real-valued coefficient.b (
ArrayLike) – Real-valued coefficient.
- Returns:
Scalar or numpy.ndarray with the same shape as kc.
- Raises:
ValueError – If kc = 0, p = 0, more than one argument is infinite, or inputs contain NaN.
Graph
Special Cases
cel(kc, p, 0, 0) = 0
cel(kc, p, a, b) = 0 for |kc| = ∞
cel(kc, p, a, b) = 0 for |p| = ∞
cel(kc, p, a, b) = sign(a) ∞ for |a| = ∞
cel(kc, p, a, b) = sign(b) ∞ for |b| = ∞
Related Functions
- With kc² = 1 - m and p = 1 - n:
K(m) = cel(kc, 1, 1, 1) = cel1(kc)
E(m) = cel(kc, 1, 1, kc²) = cel2(kc, 1, kc²)
D(m) = cel(kc, 1, 0, 1)
Π(n, m) = cel(kc, p, 1, 1)
References
Bulirsch, R. “Numerical Calculation of Elliptic Integrals and Elliptic Functions. III.” Numerische Mathematik 13, no. 4 (August 1, 1969): 305-15. https://doi.org/10.1007/BF02165405.
Carlson, B. C. “DLMF: Chapter 19 Elliptic Integrals.” Accessed February 19, 2025. https://dlmf.nist.gov/19.
Pornsiriprasert, Sira. Ellip: Elliptic Integrals for Rust. V. 0.5.1. Released October 10, 2025. https://docs.rs/ellip/0.5.1/ellip/index.html.