JSL: Creating formula using a variable column name

[#1]

Hi,

I want to do an actually simple thing (at least I thought so), namely to create a new column using JSL with a formula that contains a variable column name. I already tried several combinations of the commands "column, as column, name, as name, eval, parse .." and I searched the forum, but everything I tried results in an error that the formula could not be evaluated.

An example what I want to do:
"column 1" is a column in my data table.

a = "column 1";
new column("test", formula(a*2));

The column "test" should contain the formula that multiplies "column 1" with 2.

Thanks for any help,
Dahla

[#2]

@mpb: That works fine! Thanks for finding out and for the book tip!

[#3]

I tried but cant get it work on a variant.

There are two column where the user chooses in a custom dialog box, and i assign them the names of lx,ly.
I need a new column with formula

Radius = SQRT((X^2)+(Y^2))

However, when i run it, althought the new column is created, JMP prompt me
"N Items() argument must be a list", and no formula created.

Appreciate if a kind soul can advice on which part is faulty. Thanks.

customDlg << CloseWindow;
lp = colListP << GetItems;
lx = colListX << GetItems;
ly = colListY << GetItems;
 
// Are the user selections viable?
if (NItems(lp) < 1,
     Dialog("ERROR: Select one or more Parameter Columns", Button("OK")); Throw());
if (NItems(lx) != 1,
     Dialog("ERROR: You need to select an X Column", Button("OK")); Throw(),
     xVar = lx(1)     
     );
if (NItems(ly) != 1,
     Dialog("ERROR: You need to select a Y Column", Button("OK")); Throw(),
     yVar = ly(1)
     );
 
 
// *********************************************************************************
// Build New Column with new formula
// *********************************************************************************
 
dt = Current Data Table();
a = Column(dt,xvar);
b = Column(dt,yvar);
colx = ;
coly = ;
nlist = N Items(a);
For( i = 1, i <= nlist, i++,     
newColExpr = Expr(          
               dt << New Column( "Radius", Numeric,
               Formula( Root((Power(Expr(a(i)),2)+Power(Expr(b(i)),2)),2 ) )     );     
               Eval( Eval Expr( newColExpr ) );
);
);
); 

[#4]

Here's an example using the Column Dialog which gives the user the choice to select exactly 2 columns from which the Radius column will be created.

dt = Current Data Table();
cdlg = Column Dialog( clist = ColList( "Pick 2 Columns", Min Col( 2 ), Max Col( 2 ) ) );
cols = cdlg["clist"];
 
newColExpr = Expr( dt << New Column( "Radius", Numeric, Formula( Sqrt( Expr( cols&#91;1&#93; ) ^ 2 + Expr( cols&#91;2&#93; ) ^ 2 ) ) ) );
 
Eval( Eval Expr( newColExpr ) );

[#5]

Thanks for the help. Will try it out.
=)