Evaluates the real modified Bessel function of the first kind of order one I1(x).
Synopsis
#include <imsl.h>
float imsl_f_bessel_I1 (float x)
The type double procedure is imsl_d_bessel_I1.
Required Arguments
float x
(Input)
Point at which the Bessel function is to be evaluated.
Return Value
The value of the Bessel function
If no solution can be computed, NaN is returned.
Description
For large |x|, imsl_f_bessel_I1 will overflow. It will underflow near zero.
Example
The Bessel function I1(1.5) is evaluated.
#include <imsl.h>
int main()
{
float x = 1.5;
float ans;
ans = imsl_f_bessel_I1(x);
printf("I1(%f) = %f\n", x, ans);
}
Output
I1(1.500000) = 0.981666
Alert Errors
IMSL_SMALL_ABS_ARG_UNDERFLOW The argument should not be so close to zero that I1(x) ≈ x/2 underflows.
Fatal Errors
IMSL_LARGE_ABS_ARG_FATAL The absolute value of x must not be so large that e|x| overflows.
