title: Add a column to an existing matrix
body: <p>I have created a matrix of 100 random numbers</p>
  
  <pre><code>set.seed(1)
  datae=matrix( rnorm(100*1,mean=0,sd=1), 100, 1) 
  </code></pre>
  
  <p>Now I need to add another column to this matrix with a sum of the previous row, keeping the first row value <code>[1,2]</code> same as <code>[1,1]</code></p>
  
  <p>E.g.: the result would be cumulative like:</p>
  
  <pre><code>#           [,1]       [,2]
  #[1,] -0.6264538 -0.6264538
  #[2,]  0.1836433 -0.4428105
  #[3,] -0.8356286 -1.2784391
  #[4,]  1.5952808  0.3168417
  #[5,]  0.3295078  0.6463495
  #[6,] -0.8204684 -0.1741189
  # ...
  </code></pre>
  
  <p>I am a newbie and have been trying this for the last 45 minutes.</p>