Get Column Name Formula

You need to provide some sample data Anonymous - but I'm betting the right way to do this is to normalize the data with an unpivot operation. If the values are of a similar nature, they should be in 1 column with the attribute in another, not in 4 columns. Then this is a snap.

 

 

 

each let
   varMinValue = [Min Value]
in
Table.SelectRows(
   [All Rows], 
   each [Value] = varMinValue
   )[Attribute]{0}

 

 

It takes this:

and returns this:

 

Which is now a normalized table, and will make it easier to work with in DAX. The DAX model doesn't work with coluimns like Excel does. Neither does Power Query for that matter.

 

What is normalizing data?
See the Normalizing an example table section of this paper

 

But some sample data and expected output would be helpful.

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How to provide sample data in the Power BI Forum - Provide data in a table format per the link, or share an Excel/CSV file via OneDrive, Dropbox, etc.. Provide expected output using a screenshot of Excel or other image. Do not provide a screenshot of the source data. I cannot paste an image into Power BI tables.

 

Full M code for my query:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WSixOUdJRMgRiE1MgYQHElkqxOtFK5alFQLYREJuBxXSUDMDiQA1p6UCeMVQGpMNEKTYWAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Data = _t, A = _t, B = _t, C = _t, D = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"A", Int64.Type}, {"B", Int64.Type}, {"C", Int64.Type}, {"D", Int64.Type}}),
    #"Unpivoted Other Columns" = Table.UnpivotOtherColumns(#"Changed Type", {"Data"}, "Attribute", "Value"),
    #"Grouped Rows" = Table.Group(#"Unpivoted Other Columns", {"Data"}, {{"Min Value", each List.Min([Value]), type number}, {"All Rows", each _, type table [Data=nullable text, Attribute=text, Value=number]}}),
    #"Added Custom" = Table.AddColumn(#"Grouped Rows", "Min Value Attribute", each let
   varMinValue = [Min Value]
in
Table.SelectRows([All Rows], each [Value] = varMinValue)[Attribute]{0}, Text.Type),
    #"Expanded All Rows" = Table.ExpandTableColumn(#"Added Custom", "All Rows", {"Attribute", "Value"}, {"Attribute", "Value"})
in
    #"Expanded All Rows"

How to use M code provided in a blank query:
1) In Power Query, select New Source, then Blank Query
2) On the Home ribbon, select "Advanced Editor" button
3) Remove everything you see, then paste the M code I've given you in that box.
4) Press Done
5) See this article if you need help using this M code in your model.

Anonymous , you might want to try

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("PY7BEQAhCAN74e1Hg6i1MPbfxhEY7xOZJKy4CyBNbIXoCekqt7msztlCJiM76RqNjBQ10cVmjQZI0CLEE+6kDEa7upwna7DCJJc1I3egtn7uOyoX8jJ9H+XCCu79AA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [A = _t, B = _t, C = _t, D = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"A", Int64.Type}, {"B", Int64.Type}, {"C", Int64.Type}, {"D", Int64.Type}}),
    #"Added Custom" = let cols = Table.ColumnNames(#"Changed Type") in Table.AddColumn(#"Changed Type", "Min Column", each let values = Record.FieldValues(_)
 in cols{List.PositionOf(values, List.Min(values))})
in
    #"Added Custom"