Let JMP script for you. If you have JMP16 run recode once and use enhanced log to capture the script:
or you could check if red triangle option allows you to save the script to script window for example:
Names Default To Here(1);
dt = Data Table("Big Class");
dt << Begin Data Update;
col1 = dt << New Column(dt:sex);
col1 << Set Name("sex 2");
dt << Move Selected Columns({col1}, after(dt:sex));
dt << Recode Column(
dt:sex,
{Map Value(_rcOrig, {"F", "FF", "M", "MM"}, Unmatched(_rcNow))},
Update Properties(1),
Target Column(col1)
);
dt << End Data Update;
-Jarmo