i0

Modified Bessel function of order zero.

SYNOPSIS:

double x, y, i0();
y = i0(x);

DESCRIPTION:

Returns a modified Bessel function of order zero of the argument.

The function is defined as i0(x) = j0(ix).

The range is partitioned into the two intervals [0,8] and (8, infinity). Chebyshev polynomial expansions are employed in each interval.

ACCURACY:
                      Relative error:
arithmetic   domain     # trials      peak         rms
    DEC       0,30         6000       8.2e-17     1.9e-17
    IEEE      0,30        30000       5.8e-16     1.4e-16