title: Sum by Rows in R
body: <p>Let me reclaim my question, how I can sum the numbers by row, and list the sum follow by the last column, forming a new column like the second table (sum = a + b+ c + d + e)? </p>
  
  <p>And I also want to know what if some of the values are N/A, can I still treat them as numbers?</p>
  
  <p>Sample input:</p>
  
  <pre><code>     a          b           c          d            e
  1    90         67          18         39           74
  2    100        103         20         45           50 
  3    80         87          23         44           89
  4    95         57          48         79           90
  5    74         81          61         95           131
  </code></pre>
  
  <p>Desired output:</p>
  
  <pre><code>     a          b           c          d            e    sum
  1    90         67          18         39           74   288
  2    100        103         20         45           50   318
  3    80         87          23         44           89   323
  4    95         57          48         79           90   369
  5    74         81          61         95           131  442 
  </code></pre>