title: How to avoid "Error in stripchart.default(x1, ...) : invalid plotting method" error?
body: <p>I have a simple, single data file <code>test.txt</code> which contains:</p>
  
  <pre><code>1  
  5  
  7  
  9  
  11 
  </code></pre>
  
  <p>I want to plot this file with index numbers. I have tried the following:</p>
  
  <pre><code>mydata&lt;-read.table("test.txt")
  sq&lt;-seq(1,5)
  x&lt;-data.frame(sq)
  plot(x,mydata)
  </code></pre>
  
  <p>But the plot is not generated. Instead, an error message is shown:</p>
  
  <blockquote>
    <p>Error in stripchart.default(x1, ...) : invalid plotting method</p>
  </blockquote>
  
  <p>Can you point out what I'm doing wrong, or suggest a better solution?</p>