title: Underflow in R, sum of logartihm of probabilities
body: <p>How  to calculate the logarithm of the sum of the probabilities, i.e. ln(p1 + p2), where p1 = a very small number and p2 = a very small number.  Using the values of lp1 = ln(p1) and lp2 = ln(p2)</p>
  
  <p>If you p1 and p2 are very small numbers underflow will happen. How to avoid this?</p>