title: Using combine() & aperm() function for training -- issue with first argument, must be an array
body: <p>i'm trying to create a training set by combining two lists and making it into an array, then combing two arrays using aperm but im getting an error stating:</p>
  <pre><code>Error in aperm.default(combine(train_Set), c(1, 2)) : invalid first argument, must be an array
  </code></pre>
  <p>Here is what the code looks like below:</p>
  <pre><code>train_Set &lt;- c(Smiling[1:50], Non_smiling[1:50])
  train&lt;-aperm(combine(train_Set), c(1,2))
  </code></pre>
  <p>I'm not sure if this is done correctly, can anyone give me input as to why im getting this error and how I can correct this?</p>