bessel_i1_real_vectorreturns an array of values for the modified Bessel function .
For full information please refer to the NAG Library document for s18at
- xfloat, array-like, shape
The argument of the function, for .
- ffloat, ndarray, shape
, the function values.
- ivalidint, ndarray, shape
contains the error code for , for .
is too large. contains the approximate value of at the nearest valid argument. The threshold value is the same as for = 1 in
- (errno )
On entry, .
- (errno )
On entry, at least one value of was invalid.
Check for more information.
bessel_i1_real_vectorevaluates an approximation to the modified Bessel function of the first kind for an array of arguments , for .
Note: , so the approximation need only consider .
The function is based on three Chebyshev expansions:
For small , . This approximation is used when is sufficiently small for the result to be correct to machine precision.
For large , the function must fail because cannot be represented without overflow.
NIST Digital Library of Mathematical Functions