title: Sum a list of matrices
body: <p>I have a list where each element is a 5*5 matrix. Eg</p>
  
  <pre><code>[[1]]   
             V1          V2          V3          V4          V5      
        [1,]   0.000000   46.973700   21.453500  338.547000   10.401600 
        [2,]  43.020500    0.000000  130.652000  840.526000   56.363700 
        [3,]  12.605600  173.238000    0.000000  642.075000   19.628100 
        [4,] 217.946000  626.368000  481.329000    0.000000  642.341000 
        [5,] 217.946000  626.368000  481.329000    0.000000  642.341000 
  [[2]]   
             V1          V2          V3          V4          V5      
        [1,]   0.000000   47.973700   21.453500  338.547000   10.401600 
        [2,]  143.020500    0.000000  130.652000  840.526000   56.363700 
        [3,]  312.605600  17.238000    0.000000  642.075000   19.628100 
        [4,]  17.946000  126.368000  481.329000    0.000000  642.341000
        [5,] 217.946000  626.368000  481.329000    0.000000  642.341000  
  ...
  </code></pre>
  
  <p>How can I use an apply-like function to sum matrix [1] to [n],  and return a 5*5 matrix as a result (each element is a sum of the corresponding elements in each of the matrix in the list) ?</p>