-called RPN mathematics (see <a href="ReversePolishMath.html#rpnMathematics">rpn Mathematics</a>), but
you cannot blend the columns.  For example, you cannot easily form the
ratio y/x in Gri.  (Actually, you can, by looping through your data and
doing the calculation index by index, but if you knew that already you
wouldn't need to be reading this section!)  Such blending is trivial in
the operating system, though, as in the following Gawk example (see <a href="SystemTools.html#Awk">Awk</a>).
<p>
<TABLE SUM