Filtering Dataframe date column

General Usage
1

I have a dataframe formed by reading in a CSV file as df3 = CSV.read(“data//weight_filtered.csv”, dateformat=“yyyy-mm-dd”.
Row │ Date Data
│ Date Float32
─────┼─────────────────────
1 │ 2022-07-01 201.1
2 │ 2022-07-08 202.1
3 │ 2022-07-15 203.0
4 │ 2022-07-22 200.0
5 │ 2022-07-29 200.8
6 │ 2022-07-05 202.8
This yielded the dataframe above. I would like to filter ths by dates less than say 2022-07-22. Having floundered around with different searches and forums I haven’t had any luck or managed to find a way myself, apart from editing the original CSV file. I’m sure I’m missing something simple but any help would be welcome.
Julia 1.9.3 with CSV v0.10.11

2

Try

filter(df3) do row
   row.Date >= DateTime("2022-07-22")
end
2 Likes
3 
julia> df
6×2 DataFrame
 Row │ date        data    
     │ Date        Float64
─────┼─────────────────────
   1 │ 2022-07-01    201.1
   2 │ 2022-07-08    202.1
   3 │ 2022-07-15    203.0
   4 │ 2022-07-22    200.0
   5 │ 2022-07-29    200.8
   6 │ 2022-07-05    202.8



julia> df[df.date .>= df[4,1],:]
2×2 DataFrame
 Row │ date        data    
     │ Date        Float64
─────┼─────────────────────
   1 │ 2022-07-22    200.0
   2 │ 2022-07-29    200.8

subset(df,:date=>x-> x .>= Date("2022-07-22"))
4

subset(df3, "Date" => ByRow(<=(Date(2022,7,22))))

I think DataFramesMeta.jl also has some helper tools to remove the ByRow call.

1 Like
5

Here’s how I’d use filter! (the ! indicates it modifies your existing DataFrame):

julia> using DataFrames, Dates

julia> df = DataFrame(x = Date(2000):Day(1):Date(2000, 1, 10))
10×1 DataFrame
 Row │ x
     │ Date
─────┼────────────
   1 │ 2000-01-01
   2 │ 2000-01-02
   3 │ 2000-01-03
   4 │ 2000-01-04
   5 │ 2000-01-05
   6 │ 2000-01-06
   7 │ 2000-01-07
   8 │ 2000-01-08
   9 │ 2000-01-09
  10 │ 2000-01-10

julia> filter!(:x => >(Date(2000, 1, 5)), df)
5×1 DataFrame
 Row │ x
     │ Date
─────┼────────────
   1 │ 2000-01-06
   2 │ 2000-01-07
   3 │ 2000-01-08
   4 │ 2000-01-09
   5 │ 2000-01-10
6

Hi Nils, Thanks for the prompt reply which works beautifully. Jeff

1 Like
7

Hi Tyler, Thanks for the prompt reply and solution, Jeff

8

Hi rocco, Thanks for the solution, Jeff

9

Hi Florian, Thanks for the speedy solution, Jeff