public IEnumerable <KeyValuePair <Guid, double> > recommend(
IEnumerable <UserProfile> profiles,
ISimilarityScorer similarity,
UserProfile current)
{
var totals = new Dictionary <Guid, double> ();
foreach (UserProfile other in profiles)
{
if (other == current)
{
continue; // skip the current user profile
}
double score = similarity.Calculate(current, other);
var R = other.ItemHistory.Except(current.ItemHistory);
//only score items NOT in current user's history
foreach (Guid itemId in R)
{
if (!totals.ContainsKey(itemId))
{
totals[itemId] = 0.0;
}
totals[itemId] += score;
}
}
return(totals.OrderByDescending(pair => pair.Value));
}
public IEnumerable <KeyValuePair <Guid, double> > recommendUsingLinq(
IEnumerable <UserProfile> preferences,
ISimilarityScorer similarity,
UserProfile currentUserPref)
{
var scores = from pref in preferences
where pref != currentUserPref // skip current user
let score = similarity.Calculate(currentUserPref, pref)
//only score items that the user has no preferences
from itemId in pref.ItemHistory.Except(currentUserPref.ItemHistory)
select new {
Score = score,
NoPrefItemId = itemId
};
return((from item in scores
group item by item.NoPrefItemId into grp
select new KeyValuePair <Guid, double>(grp.Key, grp.Sum(i => i.Score)))
.OrderByDescending(pair => pair.Value));
}
