Help with Date_request in Date.IsInPreviousNMonths

[Anders_G]

Hi,

I'm trying to manage my data imports with date filters. I want to import X months in the past from the previous year. I've read you can change the date_request in the Date.IsInPreviousNMonths([date_request], 2) function.

I've tried creating a custom date query from a blank query and giving it today's date one year in the past. I've named the query Datefilter.

My custom function then looks like this.

= Table.SelectRows(Dataset_(LY)_View, each Date.IsInPreviousNMonths(Datefilter, 2))

However, it doesn't return any data. What am I doing wrong?

[v-yueyunzh-msft]

Hi , @Anders_G 

The "Date.IsInPreviousNMonths" function is automatically compared with the current time of the system, and the comparison date cannot be customized.

For more information, you can refer to:
Date.IsInPreviousNMonths - PowerQuery M | Microsoft Learn

If you want to  import X months in the past from the previous year .  I think you need to calculate the days between two days and then compare the days to filter your table.

Best Regards,

Aniya Zhang

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly

[Anders_G]

Thank you for the clarification.

If you want to  import X months in the past from the previous year .  I think you need to calculate the days between two days and then compare the days to filter your table.

I would be very grateful if you could explain the process in more detail. I have no real knowledge of M or SQL. I mostly copy and paste what I can find on this forum. 

[v-yueyunzh-msft · Accepted solution]

Hi , @Anders_G 

Accoding to your description, you want to filter the previous N months od the last year. Right?

I mean this , you can put this in "Advanced Editor" in Power Query Editor:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("Tc3BDQAhCETRXjib4ODqQi3G/ttYJJrl+vIzMydJFWEwqBBolQsu3UnkGsLGtpbQGLoNTwrrCZEsHsYPnc3h1SOw2HfS5lPrAw==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t, value = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date", type date}, {"value", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", (x)=>if Duration.Days(Date.AddDays(Date.From(Date.From(DateTime.LocalNow())),-365)-x[Date]) >=0 and  Duration.Days(Date.AddDays(Date.From(Date.From(DateTime.LocalNow())),-365)-x[Date]) <=60  then 1 else -1          )
in
    #"Added Custom"

The table is like this:

Then we can filter the [Custom]=1 then we will meet your need .

Best Regards,

Aniya Zhang

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly