How to stack a variable number of series?

[#1]

The following code does not work, but it does when replacing "n_series" with 3 in the Stack command.

dt = Open( "$SAMPLE_DATA/Blood Pressure.jmp" );
n_series = 3;
dt << Stack(
	columns(:BP 8M, :BP 12M, :BP 6M, :BP 8W, :BP 12W, :BP 6W, :BP 8F, :BP 12F, :BP 6F),
	Number of Series( n_series ),
	Contiguous,
	Source Label Column( "Day" ),
	Stacked Data Column( "BP" )
);

I need to have this value variable. How to get Stack() running with a variable number of series?

Thanks!

[#2 · Accepted solution]

In this case you can try using Eval()

Names Default To Here(1);

n_series = 3;

dt = Open("$SAMPLE_DATA/Blood Pressure.jmp");

dt_stacked = dt << Stack(
	columns(:BP 8M, :BP 12M, :BP 6M, :BP 8W, :BP 12W, :BP 6W, :BP 8F, :BP 12F, :BP 6F),
	Number of Series(Eval(n_series)),
	Contiguous,
	Source Label Column("Day"),
	Stacked Data Column("BP")
);

More general solution is to evaluate the value inside the expression

Names Default To Here(1);

n_series = 3;

dt = Open("$SAMPLE_DATA/Blood Pressure.jmp");

dt_stacked = Eval(EvalExpr(dt << Stack(
	columns(:BP 8M, :BP 12M, :BP 6M, :BP 8W, :BP 12W, :BP 6W, :BP 8F, :BP 12F, :BP 6F),
	Number of Series(Expr(n_series)),
	Contiguous,
	Source Label Column("Day"),
	Stacked Data Column("BP")
)));