title: How to create barplot from dataframe
body: <p>I could not create barplot with following data frame</p>
  
  <pre><code>                    Age     Male.Average   Female.Average
     ---------------------------------------------------------    
  1:       0-19 Childhood     20.29543       18.14773
  2:    20-39 Young Adult     22.35352       22.41548
  3: 40-64 Mid Aged Adult     23.75663       23.64908
  4:     65-84 Senior Age     21.45002       21.71446
  5:   85+ Old Senior Age     21.72200       21.31565
  </code></pre>
  
  <p>I want to create grouped barplot like x= age, y= male.average, female.average in beside. It gives error:</p>
  
  <blockquote>
    <p>Error in <code>barplot.default(d) : 'height' must be a vector or a matrix</code></p>
  </blockquote>