Create column with other column titles

[mckee]

Hi all

I'm new to PQ and M-Code.

I want to create a new column. It should store the name of other columns, depending on the data inside these other columns.

1. Columns are oldest to newest (left to right) and contain quantities (currently stored as text, but I can switch to numeric, doesn't matter for my purpose)
2. I want to identify the newest (=most right) column which contains data (<> null and <> "" and <> 0) for each line
3. I want to transfer the name of the column found in step 2 into a new column for each line

screenshot

Thank you for any inputs in advance and feel free to ask back.
Marc

[latimeria]

That)s right.

Streamline version

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlXSUTIDYnOlWJ1oJUsgyxiITcA8QwMg0wjENzSCCFiABECiSrGxAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"2020/1" = _t, #"2020/2" = _t, #"2020/3" = _t]),
    #"Added Index" = Table.AddIndexColumn(Source, "Index", 0, 1, Int64.Type),
        #"Unpivoted Other Columns" = Table.UnpivotOtherColumns(#"Added Index", {"Index"}, "Attribute", "Value"),
        #"Filtered Rows1" = Table.SelectRows(#"Unpivoted Other Columns", each [Value] <> null and [Value] <> ""),
        #"Grouped Rows" = Table.Group(#"Filtered Rows1", {"Index"}, {{"Max", each List.Max([Attribute]), type text}}),
    #"Added Custom" = Table.AddColumn(#"Added Index", "Custom", each #"Grouped Rows"[Max] {List.PositionOf(#"Grouped Rows"[Index], [Index])}),
    Cleanup = Table.RemoveColumns(#"Added Custom",{"Index"})
in
    Cleanup

[mckee]

Like I said, I'm a beginner, so I wasn't able to work with the M-Code samples.

But what I could read from it was enough to get the idea, and the I re-created the process via PowerQuery's click-the-GUI buttons 🙂

Thank you for the help!

Now I need to find a way to work with changing column titles in the source file(s)...

[latimeria · Accepted solution]

Try with this code. One way to sort out the issue

update: I sligthly change the code to meet your requirements. You are not ooking for the max value.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlXSUTIDYnOlWJ1oJUsgyxiITcA8QwMg0wjENzSCCFiABECiSrGxAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"2020/1" = _t, #"2020/2" = _t, #"2020/3" = _t]),
    #"Added Index" = Table.AddIndexColumn(Source, "Index", 0, 1, Int64.Type),
    #"Unpivoted Other Columns" = Table.UnpivotOtherColumns(#"Added Index", {"Index"}, "Attribute", "Value"),
    #"Filtered Rows1" = Table.SelectRows(#"Unpivoted Other Columns", each [Value] <> null and [Value] <> ""),
    #"Grouped Rows" = Table.Group(#"Filtered Rows1", {"Index"}, {{"Max", each List.Max([Attribute]), type text}, {"Rows", each _, type table [Index=number, Attribute=text, Value=text]}}),
    #"Added Index for columns names" = Table.TransformColumns( #"Grouped Rows", {"Rows", each Table.AddIndexColumn(_, "I")}),
    #"Expanded Rows" = Table.ExpandTableColumn(#"Added Index for columns names", "Rows", {"Attribute", "I", "Value"}, {"Attribute", "I", "Value"}),
    #"Filtered Rows - hold max" = Table.SelectRows(#"Expanded Rows", each [Max] = [Attribute]),
    #"Merged Queries Added Index withfiltered rows" = Table.NestedJoin(#"Added Index", {"Index"}, #"Filtered Rows - hold max", {"Index"}, "Filtered Rows", JoinKind.LeftOuter),
    #"Expanded Filtered Rows" = Table.ExpandTableColumn(#"Merged Queries Added Index withfiltered rows", "Filtered Rows", {"I"}, {"I"}),
    #"Added Columns Names" = Table.AddColumn(#"Expanded Filtered Rows", "Names", each Table.ColumnNames(Source){[I]}),
    Cleanup = Table.RemoveColumns(#"Added Columns Names",{"Index", "I"})
in
    Cleanup

[AlexisOlson]

This is solid logic. I think you can streamline it by dropping your [Rows] column entirely in the Group By though. Your [Max] column should already have the latest month and you can skip straight to the merge.