BesselI function
BESSELI(x,n) returns the modified Bessel function of the first kind of order n evaluated at x. x can be any real number. n is the order of the Bessel function; if it is not an integer, it is truncated.
The modified Bessel function of the first kind is related to the Bessel function of the first kind by:
$$ I_n(x) = i^{-n} J_n(ix) = \frac{1}{\pi}\int_0^\pi e^{x\cos\theta}\cos(n\theta)\,d\theta $$
Unlike BESSELJ, the modified Bessel function BESSELI does not oscillate and grows without bound as x increases.
Examples
BESSELI(0,0) equals 1
BESSELI(1,0) equals 1.2660659
BESSELI(1,1) equals 0.5651591
Calculator
Graph
Graph for different order parameters n
