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Anonymous's avatar
Anonymous
Not applicable
7 years ago
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Looping through a table in an m function

I have a function that takes in a table name, and I want to loop through the 2 fields in the table, and create a string that has a comma between the 2 fields for a line and a new line for each row. E...
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  • d_gosbell's avatar
    d_gosbell
    7 years ago

    So given the edits to your question I would do this in two steps, first doing an add column to produce the row by row operation where you subtract 1000 from the year and multiply the price by 2. Then do a List.Accumulate over that column adding line breaks between each row.

     

    eg

     

    let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjIwMFDSUTI1VYrVAfMMQTxzGM8IxDNQio0FAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [Year = _t, Price = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Year", Int64.Type}, {"Price", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", each Number.ToText([Year] - 1000) & "," & Number.ToText( [Price]*2)),
    Custom = #"Added Custom"[Custom],
    result = List.Accumulate(Custom, "", (state, current) => state & current & "#(cr)#(lf)"  )
in
    result

    PS. The Binary.FromText in the first line is just the pasted data from your question

Anonymous's avatar
Anonymous
Not applicable
7 years ago

But I am not trying to add a column, I am not in any way modifying the source table. I just want the values so I can create a string out of them after doing some calculations (the one string for the entire table). Seems kind of weird that nobody seems to know how to loop through a table, I would have thought that would be one of the most important functions in power query!

d_gosbell's avatar
d_gosbell
Super User
7 years ago
Anonymous wrote:

But I am not trying to add a column, I am not in any way modifying the source table. I just want the values so I can create a string out of them after doing some calculations (the one string for the entire table). Seems kind of weird that nobody seems to know how to loop through a table, I would have thought that would be one of the most important functions in power query!

It would probably have been easier to understand if you provided a few rows of example data and the output you were after. I though you wanted to produce a new string per row. But if you want to produce a single string after looping through all the rows in a table then you could look at calling Table.ToList then using List.Accumulate 

 

Reza has a great post on List.Accumulate here including a number of examples one of which shows using it to do a concatenate operation.