[R] x-y plot as an histogram

[Federico Abascal]

Hi,

I am investigating a problem for which I found no solution.
I have a matrix with two columns. I have plotted it as an x-y plot  
(plot(matrix[,1],matrix[,2])
But this is not apropriate for my purposes. I need to group the data  
in matrix[,1] into groups (as an histogram would do). Then I have to  
calculate the average of matrix[,2] for each group.

Before starting with loops and loops I would like to know if is there  
some way to do this easily with R.

Thanks in advance!
Federico