title: TimeSeries vs XYSeries AchartEngine
body: <p>XYSeries add method only accepts add(double, double). Why can't it accept add(java.util Date, double) similar to the TimeSeries.</p>
  
  <p>I would like to plot X-axis = dates, 2 Y-axis (left and right) = values but the problem I experienced was I lost the dual y-axis plot (secondary Y-axis on the right hand side) if I use the TimeSeries add method with (Date, double) values. If I use the XYSeries it allows me to do a dual y-axis plot but would not accept Dates in the X-axis.</p>
  
  <p>Code is given below:</p>
  
  <pre><code>public void addXYSeries(XYMultipleSeriesDataset dataset, String[] titles,
      List&lt;Date[]&gt; xValues, List&lt;double[]&gt; yValues, int scale) {
      int length = titles.length;
      for (int i = 0; i &lt; length; i++) {
          //XYSeries series = new XYSeries(titles[i], scale);
          TimeSeries series = new TimeSeries(titles[i]);
          Date[] xV = xValues.get(i);
          double[] yV = yValues.get(i);
          int seriesLength = xV.length;
          for (int k = 0; k &lt; seriesLength; k++) {
              series.add(xV[k], yV[k]);
          }
          dataset.addSeries(series);
      }
  }
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/arj1o.png" alt="enter image description here"></p>