I have two data sets df1,df2
> df1
 x1    y1 
  1    5
  1    2   
  1    3     
  1   10
> df2
     x2    y2 
      4    8
      4    7   
      4    9    
      4    3
I want to match  y1  in df1 with y2 in df2  ,if there are shared values between them ,I will merge the two data sets
in my EX ,y1 contains 3  and y2 contains 3, so the result  will be :
> df3
 x1    y1 
  1    5
  1    2   
  1    3     
  1   10
  4    8
  4    7   
  4    9    
  4    3
the merger should be based the condition (shared values only) between y1&y2 , otherwise no 
