[R] How to visualize relation between two sets of rel. frequencies?

[Stefan Sobernig]

I am looking at a data set containing two variables (x,y), each of which 
represents relative frequencies (rounded):

data.frame(x = c(0.1,0.6,0.2,0.1), y = c(0.5,0.2,0.2,0.1))

       x    y
1 0.1 0.5
2 0.6 0.2
3 0.2 0.2
4 0.1 0.1

each of the rows reflects a "relation" between x and y, for example in 
row 4: 10% of the observations in x account for 10% of the observations 
in y.

I feel embarrassed, but my mind went blank, and I can't think of a 
proper way of visualizing this "relation" based on the data above (nor 
of the appropriate terminology to phrase my question other than "by 
example").

My apologies and thanks for your hints!

//stefan