You can use Fit Y by X and then set the Group By, and then do a Flexable==>Fit Spline. Each group will have it's own Lambda slider
![spline.PNG spline.PNG](https://community.jmp.com/t5/image/serverpage/image-id/11734i4EC9BB2DD69F7F3E/image-size/large?v=v2&px=999)
Names Default To Here( 1 );
dt = Open( "$SAMPLE_DATA/big class.jmp" );
dt << Bivariate(
Y( :height ),
X( :weight ),
Fit Where( :sex == "F", Fit Spline( 1000, {Line Color( {212, 73, 88} )} ) ),
Fit Where( :sex == "M", Fit Spline( 1000, {Line Color( {66, 112, 221} )} ) )
);
Jim