I am using xgboost for a recommender system. There are 3-4 recommended content on each page. My data consists of columns like page_id and advertisement_id. Currently for every page_id, there are 3-4 rows of advertisement_id in data. Xgboost then gives me the probability of likelihood of an ad being clicked.It is known that one content(advertisement_id) from each page(page_id) is definitely clicked. I want to leverage this fact while training xgboost. How can I tell xgboost that one ad_id from each page_id is definitely clicked?Can this be done somehow by using a vector of advertisement_id for each row of page_id? 
Feeding data to Xgboost for recomender system
xgboost;recommender system