Dear all,
I have a table (that results from dependency parsing) with some rows referencing to other rows.
It looks like:

Position Word Wordclass Reference
1 xxx Adj 2
2 xxx Noun 3
3 xxx Verb 0
4 xxx Noun 3
…

I have the following question: How can I generate a dummy variable that tells me whehter the row refers to a verb? In this case, observations 2 and 4 should get 1 (they refer to the third row); observations 1 and 3 should get 0.
Thanks for any suggestions!