Storing output in an array or matrix

I have a data set which has, let's say, income by state.  I'm trying to
output income quartiles for each state into an array by doing a loop so that
I don't have to do it state by state by hand.

ie, something like

for (i in 1:50) {

quantile(subset(data,state==i)$income) -> r[i,5]   }


where the output of quantile will give 5 columns for each state.    r would
be a 50x5 matrix where each row represents state i's income quartiles.  

thanks