How to make initial phase of a tween not extreme?

[starry-abyss]

Hi,
I tween a sprite like this:

y = yTop;
var dy = (yBottom - yTop);
FlxTween.tween(this, { y: y + dy }, dy / speed, { type: FlxTween.PINGPONG, ease: FlxEase.sineInOut });

But it starts from top y position. I want it to start from any position I specify (inside the range, of course).
Is there a way?

[starry-abyss]

Solved it by tweening the phase:

// member
var phase: Float;

// init
dy = (yBottom - yTop);
phase = Math.asin((y - yTop) / dy * 2 - 1);

FlxTween.tween(this, { phase: phase + Math.PI * 2 }, dy * 2 / speed, { type: FlxTween.LOOPING });

and then calculating y manually with:

// update
y = ((Math.sin(phase) + 1) / 2 * dy) + yTop