It seems that having a recommended list that is for example 9, 23, 8 or 8 , 9 , 23 will give same NDGC , since it just have to be within the relevant list . NDGC usually being used in ranking lists , that is why I think relevant 0 or 1 won't work.
On Wed, Apr 4, 2012 at 4:23 PM, Sean Owen <[email protected]> wrote: > It does use the order: > > double discount = i == 0 ? 1.0 : 1.0 / log2(i + 1); > > The "score" you gain for recommending a relevant item decreases as you > go down the list of recommendations. > > As the comments in the code note, relevance is 1 for relevant items > and 0 for others. There is no point in showing a term multiplied by 1, > or 0. > > On Wed, Apr 4, 2012 at 10:19 PM, ziad kamel <[email protected]> wrote: >> DCG should check the order and the formula seems not , just check if >> it contains the item >> >> if (relevantItemIDs.contains(item.getItemID())) { >> cumulativeGain += discount; >> } >> >> Second thing is that it have a relevance number "rel" which the >> formula don't use. >> >> >> >> >> On Wed, Apr 4, 2012 at 3:54 PM, Sean Owen <[email protected]> wrote: >>> It's the same formula, what do you think is different? >>> >>> On Wed, Apr 4, 2012 at 9:35 PM, ziad kamel <[email protected]> wrote: >>>> Hi , I checked the code for NDCG and it seems not same as >>>> http://en.wikipedia.org/wiki/Discounted_cumulative_gain >>>> How that formula was derived ? >>>> >>>> Thanks
