Building table with JSL, issue with "New Column"

dbosch

Hi,

 

I am trying to build a table in JSL from a data file using the file's first line of data to determine the data type.  However I am not able to create new columns in script with types other than Numeric.  This works:

dt << New Column("test", Character, Nominal)

However, this (simplified example) only generates Numeric columns:

cols = {"A", "B", "C"};
type = {};
For(i = 1, i <= N Items(cols), i = i + 1,
	type[i] = Match(cols[i], 
		"A", Expr(Character), 
		Expr(Numeric);
	);
);

For(i = 1, i <= N Items(cols), i = i + 1, 
	dt << New Column(cols[i], Eval(type[i]), Nominal);
);

The expected behavior would be to create one Character column and two Numerics.  What causes the expression type[i] to be ignored here?

txnelson

Some items within a New Column() function are not evaluated when parsed, and therefore require that they are complete JSL statements when processed.  The Substitute() function allows one to do that.  Here is the code that I would use to do what you are doing:

dt = New Table( "Example" );
cols = {"A", "B", "C"};
type = {};


For( i = 1, i <= N Items( cols ), i = i + 1,
	Eval(
		Substitute(
				Expr(
					dt << New Column( cols[i], __type__, Nominal )
				),
			Expr( __type__ ), Match( cols[i], "A", Expr( Character ), Expr( Numeric ) )
		)
	)
);