julia> mpg = data("ggplot2", "mpg")
julia> total = sum(mpg["cyl"])
1378
julia> within(mpg, :(xxx = cyl ./ $total))
ERROR: InexactError()
in ./ at /Users/swade/.julia/DataFrames/src/operators.jl:686
in anonymous at /Users/swade/.julia/DataFrames/src/dataframe.jl:1389
in within! at /Users/swade/.julia/DataFrames/src/dataframe.jl:1392
in within at /Users/swade/.julia/DataFrames/src/dataframe.jl:1395
There seems to be a type error with ./