Modified Bessel functions of the first kind.
I = BESSELI(ALPHA,X) computes modified Bessel functions of the
first kind, I21KTGXR_sub_alpha(X) for real, non-negative order ALPHA
and argument X. In general, both ALPHA and X may be vectors.
The output I is m-by-n with m = lenth(X), n = length(ALPHA) and
I (k,j) = I _sub_alpha(j)(X(k)).
The elements of X can be any nonnegative real values in any order.
For ALPHA there are two important restrictions: the increment
in ALPHA must be one, i.e. ALPHA = alpha:1:alpha+n-1, and the
elements must also be in the range 0 <= ALPHA(j) <= 1000.
E = BESSELI(ALPHA,X,1) computes I _sub_alpha(X)*EXP (-X).
The relationship between the Bessel functions of the first kind is
I _sub_alpha(x) = i^(-alpha) * J _sub_alpha(i*x)
besseli(3:9,[0:.2:9.8 10:.5:20],1) generates the entire
71-by-7 table on page 423 of Abramowitz and Stegun,
"Handbook of Mathematical Functions."
See also: BESSELJ , BESSELY , BESSELK .