Weighted Mean

[JakeZw]

When I follow along the help for mean

`julia> using Statistics

julia> n=20;

julia> x=rand(n);

julia> w=rand(n);

julia> mean(x, weights(w))`

I get an error until I enter

using StatsBase

The help for mean (and all stats functions that have the weighted option) should make it clear that this method requires StatsBase.

[nalimilan]

This only happens if you have already loaded StatsBase though. Anyway the plan is to merge StatsBase and Statistics, which should fix this.