Speed trials of an Array{TimeStamp} vs DataFrame

array_v_dataframe.jl

# var is an Array{TimeStamp}
# df is a DataFrame
# each is 15850 rows long

julia> @elapsed mean(df["Open"])
0.176795466

julia> @elapsed mean(var)
0.017835577

julia> mean(var) == mean(df["Open"])
true

De-vectorized mean function

 function mean(x::Array{TimeStamp})  
    r = length(x)
    s = 0
    for v in x
      s += v.value
    end 
    s/r
  end