x::AbstractVector
y::AbstractVector
group::AbstractVector

using Vega, DataFrames, JSON

df = DataFrame()
for p in JSON.parse(readall(Pkg.dir("Vega", "vega-datasets/population.json")))
    df = vcat(df, DataFrame(; Dict(Symbol(k)=>v for (k,v) in p)...))
end

pop1900 = df[df[:year] .== 1900, :];

x = pop1900[:people]
y = pop1900[:age]
group = pop1900[:sex]

popchart(x = x, y = y, group = group)