Test xlabel in Winston plot

How to use string to lebeling x axis in Winston?

julia> plot([“a”,“b”,“c”],rand(3))
ERROR: eltype of argument #1 is not Real or Complex
in #plot#103(::Array{Any,1}, ::Function, ::Winston.FramedPlot
tractArray{T,2},AbstractString,Function,Real},N}) at C:\Users
in plot(::Winston.FramedPlot, ::Array{String,1}, ::Array{Floa

Paul