Add a geometric mean function

1 files changed, 38 insertions, 0 deletions

diff --git a/pkg/R/geomean.R b/pkg/R/geomean.R
new file mode 100644
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+++ b/pkg/R/geomean.R
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+# Copyright (C) 2015  Johannes Ranke
+# Contact: jranke@uni-bremen.de
+# This file is part of the R package pfm
+
+# This program is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation, either version 3 of the License, or (at your option) any later
+# version.
+
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+# details.
+
+# You should have received a copy of the GNU General Public License along with
+# this program. If not, see <http://www.gnu.org/licenses/>
+
+#' Calculate the geometric mean
+#'
+#' Based on some posts in a thread on Stackoverflow
+#' \url{http://stackoverflow.com/questions/2602583/geometric-mean-is-there-a-built-in}
+#' This function checks for negative values, removes NA values per default and
+#' returns 0 if at least one element of the vector is 0.
+#'
+#' @param x Vector of numbers
+#' @param na.rm Should NA values be omitted?
+#' @return The geometric mean
+#' @export
+#' @author Johannes Ranke
+#' @examples
+#' geomean(c(1, 3, 9))
+#' geomean(c(1, 3, NA, 9))
+#' \dontrun{geomean(c(1, -3, 9)) # returns an error}
+geomean = function(x, na.rm = TRUE){
+  if (any(is.na(x)) & na.rm == FALSE) stop("Removal of NA values was not requested")
+  if (any(x < 0, na.rm = na.rm)) stop("Only defined for positive numbers")
+  exp(mean(log(x), na.rm = na.rm))
+}