M Language code to calculate prior period difference for each entity

Hi Jarrodg 

You can put the following code to advanced editor in power query

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("bdE9DsMgDIbhuzBHjm3M31xF2XoBlPtfowgXqfrowvIIAy+9BznlVFYLR7ivsTDVHJ6jBwVQanFC3CDbBAOoVNKEBCCUfFQGSGR1QgEwyjqhArQFbRvFfrjwdl8/Q/Dp41pfwbePe3mUny3v+zXWSCaYy4WJDXu5FBLBYC6ZtGGxdU4qmMylUtuarWkcMdqaVgtWcxGKsmVzan+6rU2sWzin8Q2j3PMB", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t, Entity = _t, Close = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date", type date}, {"Entity", type text}, {"Close", type number}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"Entity"}, {{"Data", each Table.AddIndexColumn(_,"Index",0,1), type table }}),
    #"Expanded Data" = Table.ExpandTableColumn(#"Grouped Rows", "Data", {"Date", "Close", "Index"}, {"Date", "Close", "Index"}),
    #"Reordered Columns" = Table.ReorderColumns(#"Expanded Data",{"Entity", "Date", "Index", "Close"}),
    #"Added Custom" = Table.AddColumn(#"Reordered Columns", "Movement", each if [Index]=0 then null else [Close]-List.Max(Table.SelectRows(#"Expanded Data",(x)=>x[Entity]=[Entity] and x[Index]=[Index]-1)[Close]))
in
    #"Added Custom"

Output

Best Regards!

Yolo Zhu

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