[R] Implementation of gamma function for large number

[Richard M. Heiberger]

Use the lgamma function.

 > log(gamma(170))
[1] 701.4373
 > lgamma(170)
[1] 701.4373
 >

In typical uses of gamma(), they are multiplied or divided
by other gamma() values, bringing the final result into the
range of double precision numbers.

Also, look at beta(), which does those divisions of gamma() for
you.