Table.RowCount all rows in current table for use in a custom column equation

[Rdata]

I want a custom column where if a row in another column is blank, then return blank, but if it has ANY value, then return (1/ Total # of Rows in current Table)

I am trying this. 

= Table.AddColumn(#"Changed Type1", "Custom", each if [Merged_Use] <> null then (1 / ( Table.RowCount(Leadership_Usage_Tracking[TRT_ID]) as number)) else "")

The rows that are supposed to remain null are working fine. Anywhere that I am expecting (1/ Total # of rows), I am getting the error "A cyclic reference was encountered during evaluation."

Am I using the wrong expression to count the number of rows in this table? I also tried just [TRT_ID] (instead of prefacing the table name), but then the error is "cannot convert value to type Table", which makes me think I am using the wrong expression. 

EDIT: 

I went and tried adding an Index column and then calling the max number using List.Max, but it is BOGGING down PowerBI something bad.... 

= Table.AddColumn(#"Added Index", "Custom", each if [Merged_Use] <> null then (1/List.Max(#"Added Index"[Index])) else "")

[tackytechtom · Accepted solution]

Hi @Rdata,

Cyclic references are a bit tricky sometimes. One way to solve your issue is to save the number of rows in a step before and then reference that variable:

Before:

After:

And here the code in M:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlSK1YlWKsisqkoEs9CIksTk7MqS1OQMpdhYAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Column", type text}}),
    #"Replaced Value" = Table.ReplaceValue(#"Changed Type","",null,Replacer.ReplaceValue,{"Column"}),
    #"countrows" = Table.RowCount(#"Replaced Value"),
    #"Added Custom" = Table.AddColumn(#"Replaced Value", "Custom", each if [Column] <> null then 1 / #"countrows"
 else null)
in
    #"Added Custom"

Let me know if this helps 🙂

/Tom
https://www.tackytech.blog/
https://www.instagram.com/tackytechtom/

[Rdata]

This makes sense, thank you!