private void drawLetterGraph() {
        BarChartView chartview = (BarChartView) getActivity().findViewById(R.id.chart_view);
        BarSeries series = new BarSeries();
        for (char c='a'; c <= 'z'; c++) {
            series.addPoint(new BarSeries.LinearPoint
                    (c-'a',letterFrequencies.get(String.valueOf(c))));
        }
        series.setLineColor(0xFF0099CC);
        series.setLineWidth(4);
        chartview.addSeries(series);
}