.BG
.FN gamma
.FN lgamma
.TL
Gamma Function (and its Natural Logarithm)
.CS
gamma(x)
lgamma(x)
.AG x
numeric.  Missing values (`NA's) are allowed.
.RT
gamma or natural log of gamma function evaluated for each value in
`x'.  For positive integral values, `gamma(x)' is `(x\-1)!'.  For
negative integral values, `gamma(x)' is undefined.  Function
`lgamma' allows only positive arguments.  `NA's are returned
when evaluation would cause numerical problems.
.SP
.PP
Note that `gamma(x)' increases very rapidly with `x'. Use `lgamma'
to avoid overflow.
.EX
gamma(6)   # same as 5 factorial
.KW math
.WR
