Power Query Transform a Column based on Another Column

Question

I keep thinking this should be easy but the answer is evading me. In Excel Power Query, I would like to transform the value in each row of a column based on another column\

Answer 1

Sorry I was not so good editing the formula, this now works:

= Table.ReplaceValue(   #"Removed Columns", 
                   each [Contract Start Date],
                    each if [Contract Start Date] < #date(2019,01,01) then #date(2019,01,01) else
                          [Contract Start Date]
                    ,Replacer.ReplaceValue,
                    {"Contract Start Date"})