Previous Value in Power Query

[Anonymous]

Hi Experts

I am trying to work out the previous Value. in my data set. Previous Period is easy. [period]-1 in M. I would like to do the Previous Value formula in M

Here is my Table with expected result

Product	Date	Period	Previous Period	Value	Previous Value
0 of 9%	01/01/2021	0	-1	202	0
0 of 9%	01/01/2021	1	0	192	202

[FrankAT · Accepted solution]

Hi @Anonymous 

here is my solution:

// Table
let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjRSitWJVjIzBVPGJhDa0ARMWUCFjczNINJKsbEA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Value = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Value", Int64.Type}}),
    #"Added Index" = Table.AddIndexColumn(#"Changed Type", "Index", 0, 1, Int64.Type),
    #"Added Custom" = Table.AddColumn(#"Added Index", "Custom", each if [Index]-1 < 0 then null else List.Range(#"Added Index"[Value], [Index]-1, 1)),
    #"Expanded Custom1" = Table.ExpandListColumn(#"Added Custom", "Custom"),
    #"Removed Columns" = Table.RemoveColumns(#"Expanded Custom1",{"Index"}),
    #"Renamed Columns" = Table.RenameColumns(#"Removed Columns",{{"Custom", "Previous Value"}})
in
    #"Renamed Columns"

Take a look at:

https://exceltown.com/en/tutorials/power-bi/powerbi-com-and-power-bi-desktop/power-bi-data-sources/p...

With kind regards from the town where the legend of the 'Pied Piper of Hamelin' is at home
FrankAT (Proud to be a Datanaut)

[amitchandak]

@Anonymous , Lookup in power query?

there are few articles around it

https://eriksvensen.wordpress.com/2019/02/28/powerquery-replicate-doing-an-excel-vlookup-in-m/

[Anonymous]

Lookup is not going to work here Amit...