title: Count element in list
body: <p>I have a list item:</p>
  <p><code>var listCodeSensations = [4, 3, 2, 3, 2, 4, 3, 4, 2, 5, 2, 2, 3, 4, 5, 6, 0, 4, 8, 3, 2, 1];</code></p>
  <p>And I have in a costant file this model:</p>
  <pre><code>  static final List&lt;SensationItem&gt; sensationList = [
      SensationItem(
          code: 0,
          title: 'Formicolio / Intorpidimento'),
      SensationItem(
          code: 1,
          title: 'Sudorazione intensa'),
      SensationItem(
          code: 2, title: 'Dolore al petto'),
      SensationItem(code: 3, title: 'Nausea'),
      SensationItem(code: 4, title: 'Tremori'),
      SensationItem(
          code: 5,
          title: 'Paura di perdere il controllo',
      SensationItem(
          code: 6,
          title: 'Sbandamento / Vertigini'),
      SensationItem(
          code: 7, title: 'Palpitazioni'),
      SensationItem(
          code: 8,
          title: 'Sensazione di soffocamento'),
    ];
  }
  </code></pre>
  <p>Now I should insert this in a chartBar (from <strong>listCodeSensations</strong>) as in the next example:</p>
  <pre><code>var dataLine = [
            addCharts('Formicolio / Intorpidimento', 10), //title of sensations, count
            addCharts('Sudorazione intensa', 20), //title of sensations, count
            addCharts('Dolore al petto', 5), //title of sensations, count
            addCharts('Nausea', 14), //title of sensations, count
            addCharts('Tremori', 18), //title of sensations, count
            addCharts('Paura di perdere il controllo', 23), //title of sensations, count
            addCharts('Sbandamento / Vertigini', 6), //title of sensations, count
            addCharts('Palpitazioni', 1), //title of sensations, count
            addCharts('Sensazione di soffocamento', 12), //title of sensations, count
          ];
  </code></pre>