# ModBessel1st

Advanced Analysis Library Only

double ModBessel1st (double r, double x);

## Purpose

Computes the modified Bessel function of the first kind of order r, which is defined as follows:

which is a solution of the following differential equation:

For any integer value of order r, the function is defined for all real values of x. For any noninteger value of order r, the function is defined for nonnegative real values of x.

## Parameters

Input
Name | Type | Description
r | double-precision | The order of the function.
x | double-precision | The point at which the Bessel function is evaluated.

## Return Value

Name | Type | Description
result | double-precision | The value of the Bessel function evaluated at x.