public double UserSimilarity(long userID1, long userID2)
{
IPreferenceArray xPrefs = dataModel.GetPreferencesFromUser(userID1);
IPreferenceArray yPrefs = dataModel.GetPreferencesFromUser(userID2);
int xLength = xPrefs.Length();
int yLength = yPrefs.Length();
if (xLength <= 1 || yLength <= 1)
{
return(Double.NaN);
}
// Copy prefs since we need to modify pref values to ranks
xPrefs = xPrefs.Clone();
yPrefs = yPrefs.Clone();
// First sort by values from low to high
xPrefs.SortByValue();
yPrefs.SortByValue();
// Assign ranks from low to high
float nextRank = 1.0f;
for (int i = 0; i < xLength; i++)
{
// ... but only for items that are common to both pref arrays
if (yPrefs.HasPrefWithItemID(xPrefs.GetItemID(i)))
{
xPrefs.SetValue(i, nextRank);
nextRank += 1.0f;
}
// Other values are bogus but don't matter
}
nextRank = 1.0f;
for (int i = 0; i < yLength; i++)
{
if (xPrefs.HasPrefWithItemID(yPrefs.GetItemID(i)))
{
yPrefs.SetValue(i, nextRank);
nextRank += 1.0f;
}
}
xPrefs.SortByItem();
yPrefs.SortByItem();
long xIndex = xPrefs.GetItemID(0);
long yIndex = yPrefs.GetItemID(0);
int xPrefIndex = 0;
int yPrefIndex = 0;
double sumXYRankDiff2 = 0.0;
int count = 0;
while (true)
{
int compare = xIndex <yIndex ? -1 : xIndex> yIndex ? 1 : 0;
if (compare == 0)
{
double diff = xPrefs.GetValue(xPrefIndex) - yPrefs.GetValue(yPrefIndex);
sumXYRankDiff2 += diff * diff;
count++;
}
if (compare <= 0)
{
if (++xPrefIndex >= xLength)
{
break;
}
xIndex = xPrefs.GetItemID(xPrefIndex);
}
if (compare >= 0)
{
if (++yPrefIndex >= yLength)
{
break;
}
yIndex = yPrefs.GetItemID(yPrefIndex);
}
}
if (count <= 1)
{
return(Double.NaN);
}
// When ranks are unique, this formula actually gives the Pearson correlation
return(1.0 - 6.0 * sumXYRankDiff2 / (count * (count * count - 1)));
}
/// <p>
/// Reads one line from the input file and adds the data to a {@link FastByIDMap} data structure which maps user IDs
/// to preferences. This assumes that each line of the input file corresponds to one preference. After
/// reading a line and determining which user and item the preference pertains to, the method should look to
/// see if the data contains a mapping for the user ID already, and if not, add an empty data structure of preferences
/// as appropriate to the data.
/// </p>
///
/// <p>
/// Note that if the line is empty or begins with '#' it will be ignored as a comment.
/// </p>
///
/// @param line
/// line from input data file
/// @param data
/// all data read so far, as a mapping from user IDs to preferences
/// @param fromPriorData an implementation detail -- if true, data will map IDs to
/// {@link PreferenceArray} since the framework is attempting to read and update raw
/// data that is already in memory. Otherwise it maps to {@link Collection}s of
/// {@link Preference}s, since it's reading fresh data. Subclasses must be prepared
/// to handle this wrinkle.
protected void processLine <T>(string line,
FastByIDMap <T> data,
FastByIDMap <FastByIDMap <DateTime?> > timestamps,
bool fromPriorData)
{
// Ignore empty lines and comments
if (line.Length == 0 || line[0] == COMMENT_CHAR)
{
return;
}
var tokens = SplitLine(line);
string userIDString = tokens[0];
string itemIDString = tokens[1];
string preferenceValueString = tokens[2];
bool hasTimestamp = tokens.Length > 3;
string timestampString = hasTimestamp ? tokens[3] : null;
long userID = readUserIDFromString(userIDString);
long itemID = readItemIDFromString(itemIDString);
if (transpose)
{
long tmp = userID;
userID = itemID;
itemID = tmp;
}
// This is kind of gross but need to handle two types of storage
var maybePrefs = data.Get(userID);
if (fromPriorData)
{
// Data are PreferenceArray
IPreferenceArray prefs = (IPreferenceArray)maybePrefs;
if (!hasTimestamp && String.IsNullOrWhiteSpace(preferenceValueString))
{
// Then line is of form "userID,itemID,", meaning remove
if (prefs != null)
{
bool exists = false;
int length = prefs.Length();
for (int i = 0; i < length; i++)
{
if (prefs.GetItemID(i) == itemID)
{
exists = true;
break;
}
}
if (exists)
{
if (length == 1)
{
data.Remove(userID);
}
else
{
IPreferenceArray newPrefs = new GenericUserPreferenceArray(length - 1);
for (int i = 0, j = 0; i < length; i++, j++)
{
if (prefs.GetItemID(i) == itemID)
{
j--;
}
else
{
newPrefs.Set(j, prefs.Get(i));
}
}
data.Put(userID, (T)newPrefs);
}
}
}
removeTimestamp(userID, itemID, timestamps);
}
else
{
float preferenceValue = float.Parse(preferenceValueString, CultureInfo.InvariantCulture);
bool exists = false;
if (uniqueUserItemCheck && prefs != null)
{
for (int i = 0; i < prefs.Length(); i++)
{
if (prefs.GetItemID(i) == itemID)
{
exists = true;
prefs.SetValue(i, preferenceValue);
break;
}
}
}
if (!exists)
{
if (prefs == null)
{
prefs = new GenericUserPreferenceArray(1);
}
else
{
IPreferenceArray newPrefs = new GenericUserPreferenceArray(prefs.Length() + 1);
for (int i = 0, j = 1; i < prefs.Length(); i++, j++)
{
newPrefs.Set(j, prefs.Get(i));
}
prefs = newPrefs;
}
prefs.SetUserID(0, userID);
prefs.SetItemID(0, itemID);
prefs.SetValue(0, preferenceValue);
data.Put(userID, (T)prefs);
}
}
addTimestamp(userID, itemID, timestampString, timestamps);
}
else
{
// Data are IEnumerable<Preference>
IEnumerable <IPreference> prefs = ((IEnumerable <IPreference>)maybePrefs);
if (!hasTimestamp && String.IsNullOrWhiteSpace(preferenceValueString))
{
// Then line is of form "userID,itemID,", meaning remove
if (prefs != null)
{
// remove pref
var prefsIterator = ((IEnumerable <IPreference>)prefs.ToArray()).GetEnumerator();
while (prefsIterator.MoveNext())
{
IPreference pref = prefsIterator.Current;
if (pref.GetItemID() == itemID)
{
if (prefs is IList <IPreference> )
{
((IList <IPreference>)maybePrefs).Remove(pref);// prefsIterator.remove()
}
break;
}
}
}
removeTimestamp(userID, itemID, timestamps);
}
else
{
float preferenceValue = float.Parse(preferenceValueString, CultureInfo.InvariantCulture);
bool exists = false;
if (uniqueUserItemCheck && prefs != null)
{
foreach (IPreference pref in prefs)
{
if (pref.GetItemID() == itemID)
{
exists = true;
pref.SetValue(preferenceValue);
break;
}
}
}
if (!exists)
{
if (prefs == null)
{
prefs = new List <IPreference>(5);
data.Put(userID, (T)prefs);
}
if (prefs is IList <IPreference> )
{
((IList <IPreference>)prefs).Add(new GenericPreference(userID, itemID, preferenceValue));
}
}
addTimestamp(userID, itemID, timestampString, timestamps);
}
}
}
