Updated docstring and stdm function for variation

Author: itsdebartha

src/scalarstats.jl

@@ -404,13 +404,16 @@ span(x) = ((a, b) = extrema(x); a:b)
 
 # Variation coefficient: std / mean
 """
-    variation(x, m=mean(x))
+    variation(x, m=mean(x); corrected=true)
 
 Return the coefficient of variation of collection `x`, optionally specifying
-a precomputed mean `m`. The coefficient of variation is the ratio of the
-standard deviation to the mean.
+a precomputed mean `m`, and the optional correction parameter `corrected`.
+The coefficient of variation is the ratio of the
+standard deviation to the mean. If `corrected` is `false`,
+then `std` is calculated with denominator `n`. Else, the `std` is
+calculated with denominator `n-1`.
 """
-variation(x, m) = stdm(x, m) / m
+variation(x, m; corrected::Bool=true) = stdm(x, m; corrected=corrected) / m
 variation(x; corrected::Bool=true) = ((m, s) = mean_and_std(x; corrected=corrected); s/m)
 
 # Standard error of the mean: std / sqrt(len)