title: trying to work in R
body: <p>can anyone help me starting using R. 
  For example, I would like to change numbers of 1+2+3+4+5 with any other, likewise, I would like to write a+b+c+d+e, where any of these letter could be changed by any number. 
  So, can anyone tell me how to start?</p>
  
  <p>Thanks</p>