title: Add constant to few values in a vector - R
body: <p>I have a vector with 5 elements. I need to add a constant value 2nd, 3rd and 4th elements.</p>
  
  <pre><code>ar = c(0, 0, 0, 0, 0)
  ar = ar[2:3]+5
  </code></pre>
  
  <p>Expected output:</p>
  
  <pre><code>0 5 5 5 0
  </code></pre>