[R] x-y plot as an histogram

[Jim Lemon]

On 10/30/2009 06:12 AM, Federico Abascal wrote:
> 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.
Hi Federico,
If I understand your problem, I think you want first to use "cut":

groups<-cut(matrix[1,],breaks=???)

where ??? is the vector of breakpoints that you want. Then you can use 
whatever averaging function (AVEFUN) you want with something like "by":

by(matrix[,2],groups,AVEFUN)

Jim