public void graphDrawScale(Graphics2D g2d) {
        for(int x = (int)(this.getPreferredSize().width/2);
            x <= (int)(this.getPreferredSize().width); 
            x += (int)(xScale * xZoom))
        {
            g2d.drawLine(
                     x,
                     (int)(this.getPreferredSize().height/2) - 2,
                     x,
                     (int)(this.getPreferredSize().height/2) + 2
                    );
        }

        for(int x = (int)(this.getPreferredSize().width/2);
            x >= -(int)(this.getPreferredSize().width); 
            x -= (int)(xScale * xZoom))
        {
            g2d.drawLine(
                     x,
                     (int)(this.getPreferredSize().height/2) - 2,
                     x,
                     (int)(this.getPreferredSize().height/2) + 2
                    );
        }

        for(int y = (int)(this.getPreferredSize().height/2);
            y >= -(int)(this.getPreferredSize().height); 
            y -= (int)(yScale * yZoom))
        {
            g2d.drawLine(
                     (int)(this.getPreferredSize().width/2) - 2,
                     y,
                     (int)(this.getPreferredSize().width/2) + 2,
                     y
                    );
        }

        for(int y = (int)(this.getPreferredSize().height/2);
            y <= (int)(this.getPreferredSize().height); 
            y += (int)(yScale * yZoom))
        {
            g2d.drawLine(
                     (int)(this.getPreferredSize().width/2) - 2,
                     y,
                     (int)(this.getPreferredSize().width/2) + 2,
                     y
                    );
        }
    }