Then there are just two methods, known to me (aside from direct passing in memory or by dll):
1) Save the calculated data in Project R to a text file in format like "x, y, value" and then write a program on Processing to read the file, parse it and draw..
2) Program the calculation entirely in Processing from the start. So that it will calculate and plot everything for you.
In any of the ways, first thing that you need to do is tu have a clear understanding of how do you want the final diagram look like. So that you can arrange the screen output.
Personally I think that if R lets you put the values in a file, it would be a simplier way. Then you can go ahead and quickly use this way.
However, much more interesting, flexible and powerful way is the second one. Maybe I could have written some example code for you but i do not understand the maths behind the process, i have never worked with this. If you can tell me the equations maybe i can write some little example code... this:
d <- dist(mydata) # euclidean distances between the rows
fit <- cmdscale(d,eig=TRUE, k=2) # k is the number of dim
what is euclidian distance? is it the c = sqr(a*a + b*b)? what is cmdscale maths...
Thanks, regards from russia!