title: Invalid length error for beginner
body: <p>I have checked previous questions but couldn't find an answer</p>
  
  <pre><code> columnmean&lt;-function(y){
      n&lt;-ncol(y)
      means&lt;-numeric(n)
      for(i in 1:n){
          means[i]&lt;-mean(y[,i])
      }
      means}
  </code></pre>
  
  <p>I simply cannot understand the error, even the code seems right. Also, i get some dimension error if i input the value of n in this line    </p>
  
  <pre><code> means[i]&lt;-mean(y[,i])
  </code></pre>