title: Convert a 1D array to 2D array
body: <p>I am working on a program where I have to read the values from a textfile into an 1D array.I have been succesfull in getting the numbers in that 1D array.</p>
  
  <pre><code>m1=[1,2,3,4,5,6,7,8,9]
  </code></pre>
  
  <p>but I want the array to be </p>
  
  <pre><code>m1=[[1,2,3],[4,5,6],[7,8,9]]
  </code></pre>