private boolean isInArea(float x, float y, float touchX, float touchY, float radius) {
        float diffX = touchX - x;
        float diffY = touchY - y;
        return Math.pow(diffX, 2) + Math.pow(diffY, 2) <= 2 * Math.pow(radius, 2);
    }
Draws lines, uses path for drawing filled area on software canvas. Line is drawn with canvas.drawLines() method.
hellocharts-library/src/lecho/lib/hellocharts/renderer/LineChartRenderer.java