Oscillate Layer in an Elipse Expression

//OSCILLATE LAYER IN AN ELLIPSE:
//Custom Adjustments:
radiusDistX = 30;  //set to zero for up/down oscillation
radiusDistY = 100;  //set to zero for sideways oscillation
period = 1; 
// DON'T ADJUST
value + [Math.sin(time*period)*radiusDistX,
-Math.cos(time*period)*radiusDistY]