title: Only one number does not show anything in AndroidPlot
body: <p>I want to display line and bar graph for question/answer session attempted by user. I am using <code>AndroidPlot 0.6.0</code>. Session date time is domain and Range is count of questions answered with <code>Yes</code> or <code>No</code>. </p>
  
  <p><strong>Issue:</strong> List with single item does not show anything in the graph. For example, user first session: </p>
  
  <p><img src="https://i.stack.imgur.com/Ebx0Q.png" alt=""></p>
  
  <p>List with at least two items show graph correctly. Graph correctly shows two sessions with date as domain and count of yes/no as range:</p>
  
  <p><img src="https://i.stack.imgur.com/xQRSG.png" alt=""></p>
  
  <p><img src="https://i.stack.imgur.com/wHcVT.png" alt=""></p>
  
  <p>My Code for Line Graph is as follows:</p>
  
  <pre><code>XYSeries answeredYesSeries = new SimpleXYSeries(answeredYesList,
                  SimpleXYSeries.ArrayFormat.Y_VALS_ONLY, 
  // Y_VALS_ONLY means use the element index as the x value
                  "Answered Yes"); // Title of this series
          // Create a formatter to use for draw ing a series using
          // LineAndPointRenderer
          // and configure it from xml:
          LineAndPointFormatter series1Format = new LineAndPointFormatter();
          series1Format.setPointLabelFormatter(new PointLabelFormatter());
          series1Format.configure(getApplicationContext(),
                  R.xml.line_point_formatter_with_plf1);
  
          // add count of questions answered with yes series to the xyplot:
          xyPlot.addSeries(answeredYesSeries, series1Format);
  
          XYSeries answeredNoSeries = new SimpleXYSeries(answeredNoList,
                  SimpleXYSeries.ArrayFormat.Y_VALS_ONLY, // Y_VALS_ONLY means
                                                      // use the element
                                                          // index as the x
                                                          // value
                  "Answered No"); // Title of this series
          // Create a formatter to use for draw ing a series using
          // LineAndPointRenderer
          // and configure it from xml:
          LineAndPointFormatter series2Format = new LineAndPointFormatter();
          series2Format.setPointLabelFormatter(new PointLabelFormatter());
          series2Format.configure(getApplicationContext(),
                  R.xml.line_point_formatter_with_plf2);
  
          // add count of questions answered with no series to the xyplot:
          xyPlot.addSeries(answeredNoSeries, series2Format);
  </code></pre>
  
  <p>Does somebody have a solution?</p>