X = [[70, 30, 700],[32, 60, 480],[32, 20, 300],[20, 120, 600],[40, 120, 630], [40, 30, 520], [300, 1100, 1200], [2000, 400, 1500],[40, 180, 800]]
x_mean = sum(X)/length(X)
3-element Array{Float64,1}: 286.0 228.889 747.778
cov(X[1],x_mean[1])
MethodError: no method matching cov(::Array{Int64,1}, ::Float64) Closest candidates are: cov(::AbstractArray{T,1} where T) at statistics.jl:350 cov(::AbstractArray{T,1} where T, ::Bool) at statistics.jl:348 cov(::AbstractArray{T,1} where T, ::AbstractArray{T,1} where T) at statistics.jl:375 ... Stacktrace: [1] include_string(::String, ::String) at ./loading.jl:522
cov(X)
DimensionMismatch("arrays could not be broadcast to a common size") Stacktrace: [1] _bcs1(::Base.OneTo{Int64}, ::Base.OneTo{Int64}) at ./broadcast.jl:70 [2] _bcs at ./broadcast.jl:63 [inlined] [3] broadcast_shape at ./broadcast.jl:57 [inlined] (repeats 2 times) [4] broadcast_indices at ./broadcast.jl:53 [inlined] [5] broadcast_c at ./broadcast.jl:313 [inlined] [6] broadcast at ./broadcast.jl:455 [inlined] [7] covm(::Array{Array{Int64,1},1}, ::Array{Float64,1}, ::Bool) at ./statistics.jl:332 [8] cov(::Array{Array{Int64,1},1}) at ./statistics.jl:350 [9] include_string(::String, ::String) at ./loading.jl:522