JMP Scripting: Why doesn't my column data get sent into a Function?

Question

I am creating a JSL script for some of my datatables and need my function to act on a column.

I can get the function to act on the column during a plotting event, but not with standard operations.

Here's an example that works. This acts on the current datatable and plots up the Distribution for :Column1, which happens to be Nominal Character with 4 unique items in it.

a = Function(
        {col},                 // Function parameters
        {Default Local},       // Local variables
        Distribution(
            Nominal Distribution(
                Column( col ),
                Horizontal Layout( 1 ),
                Vertical( 0 )
            );
        );
    );

dt = Current Data Table();
a(Expr(:Column1));

Note the Expr() around :Column1. Without this, the Distribution function does not work.

---

What I'm trying to do is the following, but it doesn't work. What it should do is show the number of unique items in :Column1.

a = Function(
        {col},                 // Function parameters
        {Default Local},       // Local variables
        retval = associative array(col);
        Show(nitems(retval));
    );

dt = Current Data Table();
a(Expr(:Column1));

    Returns in Log Window:
    N Items(retval) = 0;        // Should be 4

If I run the script without trying to wrap it in a function, then it works just fine:

retval = associative array(:Column1);
Show(nitems(retval));

    Returns in Log Window:
    N Items(retval) = 4;        // My column happens to have 4 unique entries in it.

---

I'm fairly certain that my issue has something to do with namespace inside the function, but I can't seem to figure it out. Does anyone have any suggestions?

Answer 1

It is (from what I've seen) just an issue with the scoping operator : in :Column1.

Try using

a = Function(
    {col},                 // Function parameters
    {Default Local},       // Local variables
    retval = associative array(col<<Get Values)<<Get Keys;
    Show(nitems(retval));
);

dt = Current Data Table();
a(column(dt, "Column1"));

it returned

N Items(retval) = 9;