title: Error: ggplot2 doesn't know how to deal with data of class list
body: <p>I am trying to plot 100 sheet of excel data that have different X and Y values. And, I am new to R, I just started using this a month ago. For now, I am trying to plot two sheets of data from the 100 sheets. I manage to use XLConnect to import the excel file onto R. And, string out the header from each sheets, so it doesn't mess up the format</p>
  
  <p>And, I wrote this:</p>
  
  <pre><code>ggplot(data, aes(x,y)) + 
  +     geom_line(data$Sheet1, aes(x=X, y=Y), colour = "blue")  
  +     geom_line(data$Sheet100, aes(x=X, y=Y), colour = "red")
  </code></pre>
  
  <p>The R studio gives me this error message:</p>
  
  <blockquote>
    <p>Error: ggplot2 doesn't know how to deal with data of class list</p>
  </blockquote>
  
  <p>So in the end I tried data with header and without header. Eventually, both all have the same error problem. I don't know what to do. Could you please help me out?</p>
  
  <p>Thanks</p>
  
  <p><strong>Update: the problem solved</strong> </p>
  
  <pre><code>p &lt;- ggplot(data$Sheet1, aes(x=X,y=Y)) + geom_point(color='blue')
  p
  p &lt;- p + geom_point(data= data$Sheet2,aes(x=X,y=Y),color='red')
  p
  p &lt;- p + geom_point(data= data$Sheet3,aes(x=X,y=Y),color='pink') 
  p
  </code></pre>
  
  <p>and continue adding for layering the plot</p>