topic Re: Getting derivatives of a kernel smoother function in Discussions

Getting derivatives of a kernel smoother function

yvesprairie — Tue, 14 Apr 2026 15:48:28 GMT

Hi again,

I am using the kernel smoother to estimate some values and sane the prediction formula in a new column. It works very well for my purpose .

<JSL>

obj = dt_clean << Bivariate( Y( :temperature ), X( :Z_res ) ,by (:date),invisible);

obj << Kernel Smoother( 1, 1, .2, 0 );

obj << (curve[2] << Save Prediction Formula);

Now I need the derivative of this function at each point of the X variable. I can do it easily within the data table using the derivative function inside the formula editor. However, I need to do this within some JSL code. I have tried all sorts of syntax but to no avail. Any suggestions on how to do this within the community?

Many thanks for any help you can provide, Yves

Re: Getting derivatives of a kernel smoother function

Mark_Bailey — Tue, 14 Apr 2026 15:52:24 GMT

You can call this function from JSL that surfaces the feature from the Formula Editor:

Re: Getting derivatives of a kernel smoother function

yvesprairie — Tue, 14 Apr 2026 20:35:30 GMT

Thank you Mark for your quick reply. I had played around with the above function but I finally managed to get it to work by first getting the prediction formula into an expression and applying the derivative function to the name expression and then saving into a new column. For reference, here is the code. Thanks again!

formula_exp = column(4) << Get Formula;
der_expr=derivative( name expr(formula_exp), :Z_res) ;
dt_clean<< New Column( "Derivative", Formula(  Name expr(der_expr)));

Re: Getting derivatives of a kernel smoother function

hogi — Wed, 15 Apr 2026 05:19:40 GMT

wow, really nice, thank!
: - )


Names Default to Here(1);
dt = Open( "$SAMPLE_DATA/Big Class Families.jmp" );
gb = dt << Graph Builder(
	Size( 437, 413 ),
	Graph Spacing( 4 ),
	Variables( X( :height ), Y( :weight ), Overlay( :sex ) ),
	Elements( Points( X, Y, Legend( 1 ) ), Smoother( X, Y, Legend( 2 ) ) )
);
	
gbb = Report(gb)[GraphBuilderBox(1)];
gbb << updateElement(1, 1, 2, {Save Formula});

nc= n cols(dt);

myFormula = column (dt,nc) << get formula;

Eval (Eval Expr(New Column( "derivative",
	Formula(
		f = As Constant(
			Derivative( Expr(Name Expr(myFormula)),:height	));
		f;
	),
)));


gb << Add Variable( {:derivative, Role( "Y" )} )