Missing Dates

[BennyA]

I have two date columns, Report Date and Detach Date.  I have some missing Detach Dates (filled with null).  The Report Date column does not have any missing dates.  Is there a function in M Language that will populate the missing dates.  Here is a sample of the data.  The null values need to have the actual detach date (The report date of 7/27/2015 has a Detach Date of 5/21/2020) and the null vlaue should have 5/21/2020 in the cells.

The data set I am working on have several thousand rows of data and I am missing thousands of the detach dates.

Can some one help?

Report Date    DetachDate

7/27/2015	null
7/27/2015	null
7/27/2015	null
7/27/2015	null
7/27/2015	null
7/27/2015	null
7/27/2015	null
7/27/2015	null
7/27/2015	5/21/2020
7/27/2015	null
7/27/2015	null
7/27/2015	5/21/2020
7/27/2015	5/21/2020
7/27/2015	null
7/27/2015	5/21/2020
7/27/2015	5/21/2020
7/27/2015	5/21/2020
4/6/2018	null
4/6/2018	null
4/6/2018	null
4/6/2018	null
4/6/2018	null
4/6/2018	null
4/6/2018	null
4/6/2018	null
4/6/2018	null
4/6/2018	null
4/6/2018	null
4/6/2018	null
4/6/2018	4/2/2021
4/6/2018	4/2/2021

[Anonymous · Accepted solution]

Hi @BennyA ,

Consider using Fill up if the last record of each group [DetachDate] is not the null. 

In other cases, consider grouping [report date] first and then using conditional judgment to replace null.

= Table.Group(YourPreviousStepName, {"Report Date"}, {{"DetachDate", each List.Transform([DetachDate],(x) => if x = null then List.Max([DetachDate]) else x )}})

All codes in Adavance Editor.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMtc3AiIDQ1MlHaW80pwcpVidQS9oqm9kCGQbGdDEDBJNJ8cgVBkTfTOQhAWyDSNEzETfCBQOhrjFYwE=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Report Date" = _t, DetachDate = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Report Date", type date}, {"DetachDate", type date}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"Report Date"}, {{"DetachDate", each List.Transform([DetachDate],(x) => if x = null then List.Max([DetachDate]) else x )}}),
    #"Expanded DetachDate" = Table.ExpandListColumn(#"Grouped Rows", "DetachDate")
in
    #"Expanded DetachDate"

Best Regards,
Gao
Community Support Team

If there is any post helps, then please consider Accept it as the solution  to help the other members find it more quickly. If I misunderstand your needs or you still have problems on it, please feel free to let us know. Thanks a lot!

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[Migasuke]

Hi @BennyA ,

Your solution is under Fill,
Check here: