power query on how to choose selective rows according to date

[Anonymous]

hihi profs,

 need help on power query to choose rows... how to choose all date for the current month and max date for previous months

meaning to choose 12/07/2020, 12/14/2020, 12/21/2020, and 11/30/2020, 10/26/2020 and so on in this table

Index

1/13/2020

1/20/2020

1/28/2020

2/10/2020

2/24/2020

3/9/2020

3/23/2020

3/30/2020

4/6/2020

4/13/2020

4/20/2020

4/27/2020

5/4/2020

5/11/2020

5/18/2020

5/25/2020

6/1/2020

6/8/2020

6/15/2020

6/22/2020

6/29/2020

7/6/2020

7/13/2020

7/20/2020

7/27/2020

8/3/2020

8/10/2020

8/17/2020

8/24/2020

8/31/2020

9/7/2020

9/14/2020

9/21/2020

9/28/2020

10/5/2020

10/12/2020

10/19/2020

10/26/2020

11/2/2020

11/9/2020

11/16/2020

11/23/2020

11/30/2020

12/7/2020

12/14/2020

12/21/2020

[Anonymous]

Hihi profs,

what if I want only current month all dates and max date of previous 3 month or 4 months.... how to modify the code for the second answer

actually, I want to combine files, the group function seems not ok to combine files

thanks for all your kind help  profs

@Jimmy801 

[Jimmy801 · Accepted solution]

Hello @Anonymous 

this code now filters current month + max date of last 4 months

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("XdFBDgQhCATAv8x5E6TRQd8ymf9/Y/GwsXuPFSG08DyXm4ehoV3vZwtNNI9g3ljoR2GLgWAFtXW7GTy7y+xSHg3rDHfRZGEc3eaMKS9SB4joN8mJUxKnJE5JPC0YvLqSFPIiq40iL0uGdxakkC9Vw4bIoVxC0Af3ZkVL5H+lIeRD18gUcfid55f+/QI=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t]),
    YourPreviousStep = Table.TransformColumnTypes(Source,{{"Date", type date}}, "en-US"),
    SelectMonthDatesAndLastDaysOfMonth = Table.SelectRows
    (
        YourPreviousStep,
        (sel)=> if Date.IsInCurrentMonth(sel[Date]) then true else if sel[Date]> Date.StartOfMonth(Date.AddMonths(Date.From(DateTime.FixedLocalNow()), -4)) then  List.Max(List.Select(YourPreviousStep[Date], each Date.Month(_)= Date.Month(sel[Date]) and Date.Year(_)= Date.Year(sel[Date])))=sel[Date] else false
    )
in
    SelectMonthDatesAndLastDaysOfMonth

Copy paste this code to the advanced editor in a new blank query to see how the solution works. 

About your combining question or grouping... you never wrote this. So if my answers answer your question, please mark them as solution. In case you have other questions, please create a new post. You can put my reference, then I can help you also for this

If this post helps or solves your problem, please mark it as solution (to help other users find useful content and to acknowledge the work of users that helped you)
Kudoes are nice too

Have fun

Jimmy

[Jimmy801]

Hello @Anonymous 

use only Table.SelectRows to achieve this. Use this function for filtering

(sel)=> if Date.IsInCurrentMonth(sel[Date]) then true else List.Max(List.Select(YourPreviousStep[Date], each Date.Month(_)= Date.Month(sel[Date]) and Date.Year(_)= Date.Year(sel[Date])))=sel[Date]

Be aware that the YourPreviousStep has to be renamed into your real Previous step name. 

Here the complete code example

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("XdFBDgQhCATAv8x5E6TRQd8ymf9/Y/GwsXuPFSG08DyXm4ehoV3vZwtNNI9g3ljoR2GLgWAFtXW7GTy7y+xSHg3rDHfRZGEc3eaMKS9SB4joN8mJUxKnJE5JPC0YvLqSFPIiq40iL0uGdxakkC9Vw4bIoVxC0Af3ZkVL5H+lIeRD18gUcfid55f+/QI=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t]),
    YourPreviousStep = Table.TransformColumnTypes(Source,{{"Date", type date}}, "en-US"),
    SelectMonthDatesAndLastDaysOfMonth = Table.SelectRows
    (
        YourPreviousStep,
        (sel)=> if Date.IsInCurrentMonth(sel[Date]) then true else List.Max(List.Select(YourPreviousStep[Date], each Date.Month(_)= Date.Month(sel[Date]) and Date.Year(_)= Date.Year(sel[Date])))=sel[Date]
    )
in
    SelectMonthDatesAndLastDaysOfMonth

Copy paste this code to the advanced editor in a new blank query to see how the solution works.

If you have performance issues, we could create some additional step for a List.Buffer

If this post helps or solves your problem, please mark it as solution (to help other users find useful content and to acknowledge the work of users that helped you)
Kudoes are nice too

Have fun

Jimmy

[Fowmy]

@Anonymous 

To achieve what you desire, you need to add a custom column first to identify each year+month and the current year+month, then group to get the results. Paste the code below in the advanced editor of blank query and check the steps.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("XdHRDQQhCATQXvy+BBl00VrM9t/GusldnLnPFyGMsFYp92cVNw9DRf0KVTSOYF5ZaEdhk4FgBbU1uxg8u8nsrTzq1hjuosFCP7rMGUNepA4Q0W+SE6ckTkmcknhYMHh1W1LIi9xtFHlaMryxIIV8qT2sixzKKQR98N2saIr8rzSEfOg9MkUc/s3zS38/", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Dates = _t]),
    #"Filtered Rows" = Table.SelectRows(Source, each ([Dates] <> "")),
    #"Changed Type" = Table.TransformColumnTypes(#"Filtered Rows",{{"Dates", type date}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", each let

yymm = Number.From(Date.ToText([Dates],"yyyyMM")),
curr = Number.From(Date.ToText(Date.From(DateTime.FixedLocalNow()),"yyyyMM"))
in
if curr = yymm then 
yymm + Date.Day([Dates]) else
yymm),
    #"Grouped Rows" = Table.Group(#"Added Custom", {"Custom"}, {{"Count", each List.Max([Dates]), type nullable date}}),
    #"Removed Columns" = Table.RemoveColumns(#"Grouped Rows",{"Custom"})
in
    #"Removed Columns"

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