Scaled modified Bessel function of the first kind, order one.
Loading LOADSUB ALL FROM "BESMC.HTS"
or LOADSUB FROM "MATHLIB.HTS"
Usage INTEGER N
REAL X,Y
Y=FNIne(N,X)
Description
FNInereturns the value of the modified cylindrical Bessel function of the first kind and ordernofxscaled bye|x|,e-|x|In(x). The scaling is done so that the value ofIn(x) can be evaluated for arguments of large absolute value, where the absolute value ofIn(x) may be larger than MAXREAL, the largest value representable. The absolute value ofe-|x|In(x) is moderate for arguments of large absolute value.
Errors
FNInecauses an HTBasic error if its arguments are not of the types listed in the USAGE section, above.
e-|x|In(x)
See Also I0, I0e, In, K0
Note
The algorithm used computes the value ofInusing a recursion from the values ofI0 andI1. The computation time increases withnand the computation accuracy decreases withn.