but generally speaking item-based recommendation is just looking at the same problem from a different point of view. the centre of the neighbourhood is the target item.
besides, restricting the neighbourhood size seems to improve performance. srowen wrote: > > Similar to *which* item? > > It sounds like you are turning the classic recommender problem on its > side. Given an *item*, find users who might like it. Yes, you can > easily do that too, but by thinking of items as users and vice versa. > > This is not what item-based recommenders do. > > On Fri, Feb 19, 2010 at 11:32 PM, jamborta <[email protected]> wrote: >> >> what about constructing a neighborhood of >> similar items and consider users who rated the target item? >> >> something like this paper: >> >> http://portal.acm.org/citation.cfm?id=371920.372071 >> >> >> >> srowen wrote: >>> >>> It's an interesting question, and I think the quickest answer is -- >>> what item would be the center of the neighborhood? how would you >>> incorporate a notion of neighborhood? >>> >>> For users, it's clear: you construct ahead of time a neighborhood of >>> similar users and consider item's they've rated. For item-based >>> recommenders, this idea doesn't exist. >>> >>> It's easy to imagine new algorithms involving a neighborhood of items. >>> Maybe I look at each item a user knows about, construct a neighborhood >>> around that item and do something with it. These aren't canonical >>> algorithms, but you could try them. >>> >>> Sean >>> >>> On Fri, Feb 19, 2010 at 10:51 PM, jamborta <[email protected]> wrote: >>>> >>>> hi, >>>> >>>> just wondering why there is no option to set the neighbourhood size for >>>> item-based recommendation. I had a look at the implementation and it >>>> looks >>>> like you take into account all items. is there a reason for that? >>>> >>>> thanks >>>> Tamas >>>> >>>> -- >>>> View this message in context: >>>> http://old.nabble.com/item-based-recommendation-neighbourhood-size-tp27661482p27661482.html >>>> Sent from the Mahout User List mailing list archive at Nabble.com. >>>> >>>> >>> >>> >> >> -- >> View this message in context: >> http://old.nabble.com/item-based-recommendation-neighbourhood-size-tp27661482p27661852.html >> Sent from the Mahout User List mailing list archive at Nabble.com. >> >> > > -- View this message in context: http://old.nabble.com/item-based-recommendation-neighbourhood-size-tp27661482p27662057.html Sent from the Mahout User List mailing list archive at Nabble.com.
