[R] replacing NA for zero

[Silvia Lucato]

   Dear R users,



   I have a very basic query, but was unable to find a proper anwser.



   I have the following data.frame



   x     y

   2   0.12

   3   0.25

   4   0.11

   6   0.16
   7   0.20



   and, due to further calculations, I need the data to be stored as



   x     y

   1     0

   2   0.12

   3   0.25

   4   0.11

   5     0

   6   0.16
   7   0.20

   8    0



   How do I do the transformation?



   Many many thjanks in advance.