logarithm of the factorial

R/lnfactorial.R

+lnfactorial <- function(n) {
+  #' Logarithm of the factorial
+  #'
+  #' Computes the logarithm of the factorial of a positive integer.
+  #'
+  #' @aliases lnfactorial
+  #'
+  #' @usage lnfactorial(n)
+  #' @param n positive integer.
+  #' @return Numeric value. The logarithm of the factorial.
+  #' @author Pierre Santagostini, Nizar Bouhlel
+  #'
+  #' @export
+
+  if (n < 0) {
+    stop("n must be non negative")
+  }
+
+  if (n == 0) {
+    return(0)
+  }
+
+  if (n > 0) {
+    return(sum(log(1:n)))
+  }
+}