[SciPy-user] Iterative proportional fitting
Robert Kern
robert.kern at gmail.com
Thu Jan 8 18:17:28 EST 2009
On Thu, Jan 8, 2009 at 17:06, Dorian <wizzard028wise at gmail.com> wrote:
> Hi all,
> I have some marginal functions densities and I'm looking to the good way to
> find their join density function.
There are potentially an infinite number of such joint density
functions that have the same marginal densities. Adding some
constraints, like a correlation between two variables, helps, but it's
still an ill-defined problem.
> I would want to know if there is any package or script in Scipy for
> iterative proportional fitting (IPF) .
> Or any web link to help me start.
No, there is nothing in scipy for this. I think IPF applies more to
data than to distributions, per se. Estimating a joint distribution
from marginal distribution is usually called a copula, in my
experience.
http://en.wikipedia.org/wiki/Copula_(statistics)
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless
enigma that is made terrible by our own mad attempt to interpret it as
though it had an underlying truth."
-- Umberto Eco
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