M Query: Add list of months between dates

[Anonymous]

I'm trying to add rows for each month between two dates. I found some example code on the forums and tried to adapt it for my purposes, but it isn't working properly. I'm adding a custom column named "DateRange" and using the following code.

Table.AddColumn(#"Expanded people", "DateRange",  (earlier) => List.Generate(
                () => [EffortDate = earlier[award_begin_date], Counter = earlier[Months]],
                each [EffortDate] <= earlier[award_end_date],
                each [EffortDate = Date.AddMonths(earlier[award_begin_date],[Counter]),
                      Counter = [Counter] + earlier[Months]],
                each [EffortDate]),
            type {date})

It says there are no syntax errors. I expand the resulting Table column and then when I try to expand the resulting List column into new rows, I just get errors. Any help would be appreciated!

[HotChilli]

Please post some data (not a picture) and someone will help.

[Anonymous]

It's literally just three columns:

ID          award_begin_date          award_end_date
1           4/1/2019                  3/31/2020
2           6/1/2018                  5/31/2020

I want it to expand to be:

ID          award_begin_date          award_end_date       DateRange
1           4/1/2019                  3/31/2020            4/1/2019
1           4/1/2019                  3/31/2020            5/1/2019
1           4/1/2019                  3/31/2020            6/1/2019
1           4/1/2019                  3/31/2020            7/1/2019
1           4/1/2019                  3/31/2020            8/1/2019
1           4/1/2019                  3/31/2020            9/1/2019
1           4/1/2019                  3/31/2020            10/1/2019
1           4/1/2019                  3/31/2020            11/1/2019
1           4/1/2019                  3/31/2020            12/1/2019
1           4/1/2019                  3/31/2020            1/1/2020
1           4/1/2019                  3/31/2020            2/1/2020
1           4/1/2019                  3/31/2020            3/1/2020
2           6/1/2018                  5/31/2020            6/1/2018
2           6/1/2018                  5/31/2020            7/1/2018
...

[CNENFRNL · Accepted solution]

Hi, @Anonymous , don't bother to use List.Generate(); List.Accumulate() would come in handy in your senario. You might want to try,

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlTSUTLRN9Q3MjC0BDKN9Y1BbCMDpVidaCUjoIgZRNICyDRFSMYCAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ID = _t, award_begin_date = _t, award_end_date = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"ID", Int64.Type}, {"award_begin_date", type date}, {"award_end_date", type date}}),

    #"Added Custom" = Table.AddColumn(
        #"Changed Type",
        "col",
        each 
        let
            begin = Date.StartOfMonth([award_begin_date])
        in
            List.Accumulate(
                {0..(Date.Year([award_end_date])-Date.Year([award_begin_date]))*12+(Date.Month([award_end_date])-Date.Month([award_begin_date]))},
                {},
                (s,c) => s&{Date.AddMonths(begin,c)}
            )
    ),

    #"Expanded col" = Table.ExpandListColumn(#"Added Custom", "col")
        
in
    #"Expanded col"

[agusmba]

Thank you! This is exactly what I was looking for.

[mherrerag]

Life saver! Worked perfectly.

[JMelo]

This was great, thank you for sharing this!! 

It also solved my problem.

But I have this challenge to create one row for each individual day (as opposed one for for month). I'm trying to tweak the code, but it's givning me errors.

Could you please assist? 

Much appreciated!

[crossjdesign]

@JMelo  just use the List.Dates function for this, its built in to give you eactly what your lookign for, a list of all dates between a from and to date.

[Anonymous]

Brilliant! Thank you!