title: adding new column to data frame in R
body: <pre><code>  rate   len ADT trks      sigs1 slim shld lane acpt  itg lwid hwy
  1  4.58  4.99  69    8 0.20040080   55   10    8  4.6 1.20   12 FAI
  2  2.86 16.11  73    8 0.06207325   60   10    4  4.4 1.43   12 FAI
  3  3.02  9.75  49   10 0.10256410   60   10    4  4.7 1.54   12 FAI
  4  2.29 10.65  61   13 0.09389671   65   10    6  3.8 0.94   12 FAI
  5  1.61 20.01  28   12 0.04997501   70   10    4  2.2 0.65   12 FAI
  6  6.87  5.97  30    6 2.00750419   55   10    4 24.8 0.34   12  PA
  7  3.85  8.57  46    8 0.81668611   55    8    4 11.0 0.47   12  PA
  8  6.12  5.24  25    9 0.57083969   55   10    4 18.5 0.38   12  PA
  9  3.29 15.79  43   12 1.45333122   50    4    4  7.5 0.95   12  PA
  </code></pre>
  
  <p>I got a question in adding a new column, my data frame is called highway1,and i want to add a column named S/N, as slim divided by acpt, what can I do?</p>
  
  <p>Thanks</p>