title: how to set the x-axis of barplot
body: <p>This has been questioned many times like this one <a href="https://stackoverflow.com/questions/15595452/x-axis-in-barplot-in-r">X axis in Barplot in R</a></p>
  
  <p>however none helped me to solve my problem</p>
  
  <pre><code>dt&lt;- structure(c(79L, 54L, 37L, 41L, 42L, 121L, 134L, 169L, 23L, 19L, 
  22L, 19L, 25L), .Names = c("Experi_1", "Experi_2", "Experi_3", 
  "Experi_4", "Experi_5", "Experi_6", "Experi_7", "Experi_8", "Experi_9", 
  "Experi_10", "Experi_11", "Experi_12", "Experi_13"))
  </code></pre>
  
  <p>I plot my data like this </p>
  
  <pre><code>mydt&lt;- barplot(dt)
  </code></pre>
  
  <p>if I do this , it overlay twice the x-axis</p>
  
  <pre><code>axis(side=1,at=mydt[1+c(1,13)],labels=c("Experi1","Experi13"))
  </code></pre>
  
  <p>It set few of the x-axis labels automatically. I want to do it manually, for example get only mention beginning of x-axis label and end . In this case Experi1 and Experi 13. I tried to understand <em>?axis</em> and specially <em>label</em> but I could not set it to a costume as axis label as I want. </p>