[BioC] finding and averaging replicate gene records

[zhihua li]

Hi netter!

In most microarray slides a single gene will be represented by multiple 
items. Sometimes it's unforseable because they have different genbank 
accession numbers and you will not find them until you get a unigene list 
for  all your gene items.

Now I have a dataframe . The rows are gene records(accession number, 
unigene ID and expression values in different conditions) ; the 1st column 
is genbank accession numbers, the 2nd column is unigene IDs, from 3rd 
column on are different conditions). All the accession numbers are unique, 
but through unigene IDs i can find that some items, though with different 
accession numbers, are in fact sharing the same unigene ID. I would like to 
find the gene records containing replicate unigene IDs and merge them into 
one record by averaging different expression values in the same condition.

Could anyone give me a clue about how to write the code? Or are there any 
contributed functions can do this stuff?

Thanks a lot!