If you have JMP16 you could first convert the character column to date column with format pattern and then use Quarter function
Names Default To Here(1);
dt = Current Data Table();
Column(dt, 1) << Set Name("MonthYear");
Column(dt, 1) << Data Type(Numeric,
Format("Format Pattern", "<Mmm><-><YY>", 35),
Input Format("Format Pattern", "<Mmm><-><YY>")
);
dt << New Column("Q", Numeric, Ordinal, Formula(Quarter(:MonthYear)));
If you don't have JMP16 you could do "conversion list" of months and then use that instead to get Quarters
Edit:
Formula for JMPs before 16 and no conversion to first column using list of months, contains(), word() and ceiling()
dt << New Column("Q",
Numeric,
Ordinal,
Formula(
Local({month_list = (month_list = {"JAN", "FEB", "MAR", "APR", "MAY", "JUN", "JUL", "AUG", "SEP", "OCT", "NOV", "DEC"})},
Ceiling(Contains(month_list, Word(1, :MonthYear, "-")) / 3)
)
)
);
-Jarmo