title: Issues of saving an array into a plain text file
body: <p>I have built an array, such as A = [a1,a2,...aN]. How to save this array into a data file, with each element to be placed at one row. In other words, for the array A, the file should look like</p>
  
  <pre><code>a1
  a2
  a3
  ...
  </code></pre>