lgamma() function in R Language is used to compute the natural logarithm of the absolute gamma value of a numeric vector computed using the gamma function.
lgamma function is basically,

lgamma(x) = ln(factorial(x - 1))

Syntax: lgamma(x)

Parameters:
x: Non-negative Numeric Vector

Example 1:

Output:

[1] 0
[1] 0.6931472
[1] 3.178054

Example 2:

Output:

[1] 0.0000000 0.6931472 3.1780538
[1] 4.787492 6.579251 8.525161
[1] Inf Inf Inf
Warning messages:
1: value out of range in 'lgamma' 
2: value out of range in 'lgamma' 
3: value out of range in 'lgamma' 

Here, in the above code, the NaN is produced for a Negative numeric vector.