title: How to compute p-values from z-scores in R when the Z score is large (pvalue much below zero)?
body: <p>In genetics very small p-values are common (for example 10^-400), and I am looking for a way to get very small p-values (two-tailed) when the z-score is large in R, for example:</p>
  
  <pre><code>z=40
  pvalue = 2*pnorm(abs(z), lower.tail = F)
  </code></pre>
  
  <p>This gives me a zero instead of a very small value which is very significant.</p>