1 files changed, 42 insertions, 0 deletions
diff --git a/docs/reference/geomean.md b/docs/reference/geomean.md
new file mode 100644
index 0000000..9567bdb
--- /dev/null
+++ b/docs/reference/geomean.md
@@ -0,0 +1,42 @@
+# Calculate the geometric mean
+
+Based on some posts in a thread on Stackoverflow
+<http://stackoverflow.com/questions/2602583/geometric-mean-is-there-a-built-in>
+This function returns NA if NA values are present and na.rm = FALSE
+(default). If negative values are present, it gives an error message. If
+at least one element of the vector is 0, it returns 0.
+
+## Usage
+
+``` r
+geomean(x, na.rm = FALSE)
+```
+
+## Arguments
+
+- x:
+
+  Vector of numbers
+
+- na.rm:
+
+  Should NA values be omitted?
+
+## Value
+
+The geometric mean
+
+## Author
+
+Johannes Ranke
+
+## Examples
+
+``` r
+geomean(c(1, 3, 9))
+#> [1] 3
+geomean(c(1, 3, NA, 9))
+#> [1] NA
+geomean(c(1, -3, 9)) # returns an error
+#> Error in geomean(c(1, -3, 9)): Only defined for positive numbers
+```