[R] Question about manipulating quartiles

[Ajay Shah]

I know the `quantcut' function in the gregmisc package, and using it,
I'm able to use functions like aggregate to compute the mean or sd()
in each quartile.

What if I have a data frame containing x and y, and I want to make
quartiles by x, but then compute sum x / sum y in each quartile?
How does one persuade aggregate to do this?

Thanks,

-- 
Ajay Shah                                                   Consultant
ajayshah at mayin.org                      Department of Economic Affairs
http://www.mayin.org/ajayshah           Ministry of Finance, New Delhi