Returns the gamma function or the log of the gamma function.
USAGE:
gamma(x)
lgamma(x)
REQUIRED ARGUMENTS:
x:
numeric or complex object.
Missing values (NA) are allowed.
VALUE:
gamma or natural log of gamma function evaluated for each value in x.
CLASSES:
This function will be used as the default method
for classes that do not inherit a specifc method for the
function or for the
Math
group of functions.
The result will retain the class and the attributes.
If this behavior is
not
appropriate, the designer of the class should provide a method
for the function or for the
Math
group.
DETAILS:
NAs are returned when evaluation would cause numerical problems,
except that when an overflow occurs, an infinity is returned.
These are members of the Math group of generic functions.
WARNING:
gamma(x) increases very rapidly with x. Use lgamma
to avoid overflow.
BACKGROUND:
For positive integral values, gamma(x) is (x-1)!. For
negative integral values, gamma(x) is undefined.
NOTE:
See family for the family generating function Gamma used with the glm
and gam functions. See GAMMA for the functions related to the
gamma distribution: dgamma (density), pgamma (probability),
qgamma (quantile), rgamma (sample).