Searching for specific functions

Hello everybody (I'm new here)

  I am looking for 2 specific functions. The first one is a variance
formula that does not divide by n-1 (I don't want the unbiased formula,
that's it). In case it does not exist, how do I modify the default
function code? Yes, a workaround would be to multiply the result by n-1
and then divide it by n, but I'd like to use a separate function, if
possible.

  The other function I'm looking for it's a median formula like this one:

http://www.faberitius.com/prototipo/gfx/clip_image002_0000.gif

  Where "Li" is the exact lower limit of the critical interval, "nb" is
the number of cases that lie below the critical interval, "nd" the number
of cases inside the mentioned interval, and "I" is the range of the
interval itself. As you can see this formula calculates the median in
categorical structured data.

  I couldn't find any functions that match the results done by hand... is
there a contrib package out there that may help me? Should I program the
function on my own?

  Thanks in advance,

           Fabrizio Ferri Benedetti

"La mayor sabidur??a que existe es conocerse a uno mismo" - Galileo Galilei