Line.clear() doesn't work. plz help!

I am making a sketchpad.
Everything’s fine except the erase button.
It doesn’t work. T.T

Can anybody help me plz???

lineThickness = 0;
selectedColor = “0x000000”;
_root.onMouseDown = startDrawing;
_root.onMouseUp = stopDrawing;
function startDrawing() {
_root.lineStyle(lineThickness, selectedColor);
_root.moveTo(_root._xmouse, _root._ymouse);
_root.onMouseMove = drawLine;
}
function drawLine() {
this.lineTo(this._xmouse, this._ymouse);
}
function stopDrawing() {
this.onEnterFrame = null;
delete this.onMouseMove;
}

eraseButton.onPress=function(){
_root.line.clear();
}