digamma(x), x REAL with positive elements or a structure with REAL components with positive elements. |

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