/*
* LensKit, an open source recommender systems toolkit.
* Copyright 2010-2014 LensKit Contributors. See CONTRIBUTORS.md.
* Work on LensKit has been funded by the National Science Foundation under
* grants IIS 05-34939, 08-08692, 08-12148, and 10-17697.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 51
* Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
package org.grouplens.lenskit.data.history;
import it.unimi.dsi.fastutil.longs.Long2DoubleMap;
import it.unimi.dsi.fastutil.longs.Long2DoubleOpenHashMap;
import org.grouplens.lenskit.core.Shareable;
import org.grouplens.lenskit.data.event.Event;
import org.grouplens.lenskit.data.event.EventType;
import org.grouplens.lenskit.vectors.ImmutableSparseVector;
import org.grouplens.lenskit.vectors.SparseVector;
import javax.annotation.Nonnull;
import javax.inject.Inject;
/**
* Summarize a history by counting all events referencing an item. The history
* can be filtered by type prior to counting.
*
* @author <a href="http://www.grouplens.org">GroupLens Research</a>
*/
@Shareable
public final class EventCountUserHistorySummarizer implements UserHistorySummarizer {
protected final Class<? extends Event> wantedType;
/**
* Create a summarizer that counts all events.
*/
@SuppressWarnings("unused")
public EventCountUserHistorySummarizer() {
this(Event.class);
}
/**
* Create a summarizer that counts events of a particular type.
*
* @param type The type of event to count.
*/
@Inject
public EventCountUserHistorySummarizer(@EventType @Nonnull Class<? extends Event> type) {
wantedType = type;
}
@Override
public Class<? extends Event> eventTypeWanted() {
return wantedType;
}
@Override @Nonnull
public SparseVector summarize(@Nonnull UserHistory<? extends Event> history) {
Long2DoubleMap map = new Long2DoubleOpenHashMap();
for (Event e : history.filter(wantedType)) {
final long iid = e.getItemId();
map.put(iid, map.get(iid) + 1);
}
return ImmutableSparseVector.create(map);
}
@Override
public int hashCode() {
return wantedType.hashCode();
}
@Override
public boolean equals(Object o) {
if (o instanceof EventCountUserHistorySummarizer) {
EventCountUserHistorySummarizer ocs = (EventCountUserHistorySummarizer) o;
return wantedType.equals(ocs.wantedType);
} else {
return false;
}
}
}