private void sliderChanged(){
    int val = slider.getValue();
    sData.setFirstCategoryIndex(val);// my sliding dataset
    chart = ChartDrawer.draw(sData); // to draw chart again should be unnecessary
    chart.fireChartChanged();
    chartPanel.setChart(chart);
    chartPanel.revalidate();
    chartPanel.repaint();
    chartPanel.updateUI();
    repaint();
}