get age-distribution

function get_agedist(st)
    grps = (0:4, 5:16, 17:49, 50:65, 66:99)
    _data = CSV.File("sc-est2019.csv") |> DataFrame!

    # select only the relevant columns
    select!(_data, Not(8:17))
    # filter to include both male/female, state
    filter!(r -> r[:SEX] == 0 && r[:NAME] == st && r[:AGE] <= 99, _data) 
    # calculate the the age groups 
    transform!(_data, :AGE => ByRow(x -> findfirst(grp -> x in grp, grps)) => :AGEGRP)

    # group by
    gdf = groupby(_data, :AGEGRP)
    combine(gdf, :POPEST2019_CIV => sum)    
end

# test 
get_agedist("Connecticut")
# 5×2 DataFrame
#  Row │ AGEGRP  POPEST2019_CIV_sum 
#      │ Int64   Int64              
# ─────┼────────────────────────────
#    1 │      1              181710
#    2 │      2              499697
#    3 │      3             1481961
#    4 │      4              808133
#    5 │      5              586881