Error in PQ - Expression.SyntaxError: Token ')' expected

[username100]

hi everyone , new to PQ in powerBI , i keep on getting this error , Expression.SyntaxError: Token ')' expected

this is my custom column - = Table.TransformColumns(#"Grouped Rows",("First Transaction Month",Date.StartOfMonth,Date.Type)

would appreciate any insights on this, as I am stuck here, I am doing a sample customer cohort & retention analysis 

[Omid_Motamedise]

Hi, it is all about the second argument, you should provide it in a list. IF you are going to transform values on a column, you just need to use one List sign, but to change the values on more than a column, you have to provided a list including one sub list for each column, so revise your formula to=>


Transform a column = Table.TransformColumns(#"Grouped Rows",{"First Transaction Month",Date.StartOfMonth,Date.Type})


Transform two column= Table.TransformColumns(#"Grouped Rows",{{"First Transaction Month",Date.StartOfMonth,Date.Type},{"Name column 2}, each _+1})

[ZhangKun]

Table.TransformColumns(#"Grouped Rows",{"First Transaction Month", Date.StartOfMonth,Date.Type})

or 

Table.TransformColumns(#"Grouped Rows",{{"First Transaction Month", Date.StartOfMonth,Date.Type}})

For a single conversion, you can use either {} or {{}}

[watkinnc]

Try

able.TransformColumns(#"Grouped Rows",{{"First Transaction Month",Date.StartOfMonth, type date}})

--Nate