Power Query M formula language standard library: Table.AddColumn
Table.AddColumn(TABLE as table, NEWCOLUMNNAME as text, COLUMNGENERATOR as function, optional COLUMNTYPE as nullable type) as table
Table.AddColumn adds a new column to a table by calling COLUMNGENERATOR on each record. The returned value of COLUMNGENERATOR becomes the column's new value.
Example:
let
tab = #table(
{ "id", "val 1", "val 2"}, {
{ 1 , "abc" , 1111 },
{ 2 , "def" , 22 },
{ 3 , "ghi" , 333 }
}),
tab_ = Table.AddColumn(tab, "size", each
if [val 2] > 1000 then "large"
else if [val 2] > 100 then "medium"
else "small"
)
in
tab_