R's expand.grid() equivalent in Julia

expand_grid.jl

using DataFrames

"""
Create a Data Frame from All Combinations of Factor Variables (see R's base::expand.grid)

# Arguments
... Array, Dict, or Tuple containing at least one value

# Return
A DataFrame containing one row for each combination of the supplied argument. The first factors vary fastest.

# Examples
```julia
expand_grid([1,2],["owl","cat"])

expand_grid((1,2),("owl","cat"))

expand_grid((1,2)) # -> Returns a DataFrame with 2 rows of 1 and 2.
```
"""
function expand_grid(args...)
    nargs= length(args)
    
    if nargs == 0
      error("expand_grid need at least one argument")
    end

    iArgs= 1:nargs
    nmc= "Var" .* string.(iArgs)
    nm= nmc
    d= map(length, args)
    orep= prod(d)
    rep_fac= [1]
    # cargs = []

    if orep == 0
        error("One or more argument(s) have a length of 0")
    end
    
    cargs= Array{Any}(undef,orep,nargs)

    for i in iArgs
        x= args[i]
        nx= length(x)
        orep= Int(orep/nx)
        mapped_nx= vcat(map((x,y) -> repeat([x],y), collect(1:nx), repeat(rep_fac,nx))...)
        cargs[:,i] .= x[repeat(mapped_nx,orep)]
        rep_fac= rep_fac * nx
    end
    
    convert(DataFrame,cargs)
end