Accuracy of the Modified Bessel Functions

I will be using the modified bessel functions I and K ( besseli and besselk in the matlab code) and I am concerned about the accuracy of the functions. I plan to use the special case in which

nu = 0.

Calculating the bessel functions for this special case requires a different formula, and I am curious if the matlab function is still accurate.

Answer 1

[Neethu]

Can you please tell what is that formula? Actually i need to calculate modified zeroth order bessel function of first kind.It returns infinity values after 700.Can we write our own code for this function instead of built in besseli()