title: How to find the diagonal elements of a matrix?
body: <p>I have written a function to store the diagonal elements of a matrix into a vector. but the output is not as I expected. The code is:</p>
  <pre><code>diagonal &lt;- function(x) {
    for (i in nrow(x)) {
      for (j in ncol(x)) {
        if (i == j) {
          a &lt;- x[i, j]
        }
      }
    }
    print(a)
  }
  </code></pre>
  <p>I am passing a matrix to the function.
  What is wrong with the code?</p>