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Usage:
digamma(x), x REAL with positive elements or a structure with REAL
components with positive elements.
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Keywords:
transformations
digamma(x) returns the digamma function (first derivative of
log(gamma(x))) of the elements of x, when x is a REAL scalar, vector,
matrix or array with positive elements. The result has the same shape
as x.
digamma(x) is equivalent to polygamma(x,0).
When x is a structure, all of whose non-structure components are REAL
with positive elements, digamma(x) returns a structure of the same shape
and with the same component names as x with each non-structure component
transformed by digamma().
digamma(x) can also be used when x is a CHARACTER variable. The result
is a CHARACTER variable of the same shape as x describing the
transformation. See the example below.
Any element of x that is "" or starts with '@', '(', '[', '{', '<', '/'
or '\' is not modified. This can be useful for creating labels for a
transformed variable.
Examples:
Cmd> digamma(run(10)) # or polygamma(run(10),0) or polygamma(run(10))
(1) -0.57722 0.42278 0.92278 1.2561 1.5061
(6) 1.7061 1.8728 2.0156 2.1406 2.2518
Cmd> digamma(vector("x","y")) # CHARACTER argument
(1) "digamma(x)"
(2) "digamma(y)"
See also polygamma(), lgamma(), 'transformations'
Gary Oehlert
2003-01-15