

   CCuummuullaattiivvee SSuummss,, PPrroodduuccttss,, eettcc..

        cumsum(x)
        cumprod(x)
        cummax(x)
        cummin(x)

   VVaalluuee::

        A vector with the same length of `x', but whose ele-
        ments are the cumulative sums, products, minima or max-
        ima of those in `x'.  An `NA' value in `x' will the
        corresponding and following elements of the value to be
        `NA'.

   EExxaammpplleess::

        cumsum(1:10)
        cumprod(1:10)
        cummin(c(3:1,2:0,4:2))
        cummax(c(3:1,2:0,4:2))

