kei = kelvin\_kei(x) evaluates an approximation to the Kelvin function kei x. The function is based on several Chebyshev expansions. For large x, kei x is so small that it cannot be computed without underflow and the function fails.

For more information please review the s19adc function in the NAG document.


x (input, double)
The argument x of the function.
Constraint: x ≥ 0.
kei (output, double)
Approximation of the Kelvin function kei x.