Mutate-like operation for converting string and rolling mean in Julia - julia

Question

I understand how to convert string and work out a moving average in a line by line approach. But I am wondering how to do them through a mutate-like approach in a pipe style.
julia> first(d1, 10)
10×2 DataFrame
Row │ Year Exports
│ Int64 String
─────┼─────────────────────────
1 │ 1960 12.9944524843222
2 │ 1961 12.4031007751938
3 │ 1962 13.9430116004055
4 │ 1963 13.0058857232148
5 │ 1964 14.9382483265768
6 │ 1965 13.220177939017
7 │ 1966 12.9323802481308
8 │ 1967 12.8837295006449
9 │ 1968 12.2976680384088
10 │ 1969 11.9548596244419
d1.Exports = parse.(Float64, d1.Exports)
d1.Exports_4mv = runmean(d1.Exports, 4)
I wish to get something like this:
#linq d1 |>
mutate(:Exports = parse.(Float64, :Exports)) |>
mutate(:Exports_4mv = runmean(:Exports, 4))

Answer 1

Using DataFrames.jl you can do (I use -x function instead of runmean as I am not sure which package you took runmean function from):
julia> using DataFrames, Chain, DataFramesMeta
julia> d1 = DataFrame(Year=1960:1969, Exports=string.(10rand(10) .+ 10))
10×2 DataFrame
Row │ Year Exports
│ Int64 String
─────┼───────────────────────────
1 │ 1960 18.487768691740964
2 │ 1961 19.16038389519686
3 │ 1962 19.393969741723705
4 │ 1963 10.98014563868417
5 │ 1964 13.971724415708335
6 │ 1965 15.013359289888458
7 │ 1966 10.571278054318459
8 │ 1967 10.193140593100727
9 │ 1968 12.768467572044944
10 │ 1969 14.404484209802783
julia> #chain d1 begin
transform(:Exports => ByRow(x -> parse(Float64, x)) => :Exports)
transform(:Exports => (x -> -x) => :Exports_4mv)
end
10×3 DataFrame
Row │ Year Exports Exports_4mv
│ Int64 Float64 Float64
─────┼─────────────────────────────
1 │ 1960 18.4878 -18.4878
2 │ 1961 19.1604 -19.1604
3 │ 1962 19.394 -19.394
4 │ 1963 10.9801 -10.9801
5 │ 1964 13.9717 -13.9717
6 │ 1965 15.0134 -15.0134
7 │ 1966 10.5713 -10.5713
8 │ 1967 10.1931 -10.1931
9 │ 1968 12.7685 -12.7685
10 │ 1969 14.4045 -14.4045
and with DataFramesMeta.jl 0.7 release:
julia> #chain d1 begin
#transform(Exports = parse.(Float64, :Exports))
#transform(Exports_4mv = -:Exports)
end
10×3 DataFrame
Row │ Year Exports Exports_4mv
│ Int64 Float64 Float64
─────┼─────────────────────────────
1 │ 1960 18.4878 -18.4878
2 │ 1961 19.1604 -19.1604
3 │ 1962 19.394 -19.394
4 │ 1963 10.9801 -10.9801
5 │ 1964 13.9717 -13.9717
6 │ 1965 15.0134 -15.0134
7 │ 1966 10.5713 -10.5713
8 │ 1967 10.1931 -10.1931
9 │ 1968 12.7685 -12.7685
10 │ 1969 14.4045 -14.4045