About aggregates...

Hello guys,

I would like to ask if there is any way to make an aggregate function to
take a set of tuples as an input variable. I know that an actual aggregate
function receives each tuple one at a time and process it on the fly.
However I want to store tuples in an incremental fashion so as to process
them in a batch approach in the finalaggr function. Think for example
implementing logistic regression (which is an OLAP query by its nature). I
want to support it with the current features that PostgreSQL provides from
which the closest feature is an aggregate. However an aggregate function
feeds me one a tuple for each call, but I would like to have access to a
batch of tuples per function call. Is there any possible way to perform
something like this?

Thank you very much for your time,
Michael