title: Volume of a prolate spheroid
body: <p>I have a dataset with the length and width of an prolate spheroid:</p>
  
  <pre><code>df &lt;- data.frame(nr = c(1, 2, 3), length = c(4, 5, 3), width = c(2, 2, 1))
  df
  </code></pre>
  
  <p>Now I want to make an extra column with the volume. I've used the formula V = 4/3*pi*a²b (with a and b = 1/2 length and width respectively):</p>
  
  <pre><code>df$volume &lt;- (4/3)*pi*(df$length/2)^2*(df$width/2)
  </code></pre>
  
  <p>This works, but I want to know if there is maybe an inbuilt formula for this in R?</p>