title: Plotting a graph against the days of week in R
body: <p>I have a column named <code>date</code> in my data frame and another column named <code>values</code>. I want to plot the values against the days of a week. </p>
  
  <p>I know that we can get days of a week from date by using the function <code>weekdays()</code>. But I am not sure about how to plot the graph with <code>values</code>(y-axis) against the days of week(x-axis)</p>
  
  <pre><code>      Date  Values
  12-03-2006     0.5
  14-03-2006     0.6
  18-03-2006     0.9
  23-03-2006     1.1
  02-04-2006     2.1
  </code></pre>
  
  <p>I tried this</p>
  
  <pre><code>plot(weekdays(df$Date),df$values)
  </code></pre>
  
  <p>I got this error :</p>
  
  <pre><code>Error in plot.window(...) : need finite 'xlim' values
  In addition: Warning messages:
  1: In xy.coords(x, y, xlabel, ylabel, log) : NAs introduced by coercion
  2: In min(x) : no non-missing arguments to min; returning Inf
  3: In max(x) : no non-missing arguments to max; returning -Inf
  </code></pre>
  
  <p>Can anyone help me in fixing this error?</p>