Given a dataset with a factor column (X1) and a subtotal column (X2)
  X1 X2 
1  1  12  
2  2  200 
3  3  23  
4  4  86  
5  5  141  
I would like to create a graphic like this:
 
 
which gives x2 as a percentage of the X2 total, divided by X1.
Edit: clarity and adding dataset for reproducability
 
     
    
