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<div class="subTitle">org.apache.mahout.cf.taste.model</div>
<h2 title="Interface DataModel" class="title">Interface DataModel</h2>
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<div class="contentContainer">
<div class="description">
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<dl>
<dt>All Superinterfaces:</dt>
<dd><a href="../../../../../../org/apache/mahout/cf/taste/common/Refreshable.html" title="interface in org.apache.mahout.cf.taste.common">Refreshable</a>, <a href="http://docs.oracle.com/javase/7/docs/api/java/io/Serializable.html?is-external=true" title="class or interface in java.io">Serializable</a></dd>
</dl>
<dl>
<dt>All Known Subinterfaces:</dt>
<dd><a href="../../../../../../org/apache/mahout/cf/taste/model/JDBCDataModel.html" title="interface in org.apache.mahout.cf.taste.model">JDBCDataModel</a></dd>
</dl>
<dl>
<dt>All Known Implementing Classes:</dt>
<dd><a href="../../../../../../org/apache/mahout/cf/taste/impl/model/AbstractDataModel.html" title="class in org.apache.mahout.cf.taste.impl.model">AbstractDataModel</a>, <a href="../../../../../../org/apache/mahout/cf/taste/impl/model/file/FileDataModel.html" title="class in org.apache.mahout.cf.taste.impl.model.file">FileDataModel</a>, <a href="../../../../../../org/apache/mahout/cf/taste/impl/model/GenericBooleanPrefDataModel.html" title="class in org.apache.mahout.cf.taste.impl.model">GenericBooleanPrefDataModel</a>, <a href="../../../../../../org/apache/mahout/cf/taste/impl/model/GenericDataModel.html" title="class in org.apache.mahout.cf.taste.impl.model">GenericDataModel</a>, <a href="../../../../../../org/apache/mahout/cf/taste/impl/model/PlusAnonymousConcurrentUserDataModel.html" title="class in org.apache.mahout.cf.taste.impl.model">PlusAnonymousConcurrentUserDataModel</a>, <a href="../../../../../../org/apache/mahout/cf/taste/impl/model/PlusAnonymousUserDataModel.html" title="class in org.apache.mahout.cf.taste.impl.model">PlusAnonymousUserDataModel</a></dd>
</dl>
<hr>
<br>
<pre>public interface <span class="typeNameLabel">DataModel</span>
extends <a href="../../../../../../org/apache/mahout/cf/taste/common/Refreshable.html" title="interface in org.apache.mahout.cf.taste.common">Refreshable</a>, <a href="http://docs.oracle.com/javase/7/docs/api/java/io/Serializable.html?is-external=true" title="class or interface in java.io">Serializable</a></pre>
<div class="block"><p>
Implementations represent a repository of information about users and their associated <a href="../../../../../../org/apache/mahout/cf/taste/model/Preference.html" title="interface in org.apache.mahout.cf.taste.model"><code>Preference</code></a>s
for items.
</p></div>
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</ul>
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<h3>Method Summary</h3>
<table class="memberSummary" border="0" cellpadding="3" cellspacing="0" summary="Method Summary table, listing methods, and an explanation">
<caption><span id="t0" class="activeTableTab"><span>All Methods</span><span class="tabEnd">&nbsp;</span></span><span id="t2" class="tableTab"><span><a href="javascript:show(2);">Instance Methods</a></span><span class="tabEnd">&nbsp;</span></span><span id="t3" class="tableTab"><span><a href="javascript:show(4);">Abstract Methods</a></span><span class="tabEnd">&nbsp;</span></span></caption>
<tr>
<th class="colFirst" scope="col">Modifier and Type</th>
<th class="colLast" scope="col">Method and Description</th>
</tr>
<tr id="i0" class="altColor">
<td class="colFirst"><code><a href="../../../../../../org/apache/mahout/cf/taste/impl/common/LongPrimitiveIterator.html" title="interface in org.apache.mahout.cf.taste.impl.common">LongPrimitiveIterator</a></code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getItemIDs--">getItemIDs</a></span>()</code>&nbsp;</td>
</tr>
<tr id="i1" class="rowColor">
<td class="colFirst"><code><a href="../../../../../../org/apache/mahout/cf/taste/impl/common/FastIDSet.html" title="class in org.apache.mahout.cf.taste.impl.common">FastIDSet</a></code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getItemIDsFromUser-long-">getItemIDsFromUser</a></span>(long&nbsp;userID)</code>&nbsp;</td>
</tr>
<tr id="i2" class="altColor">
<td class="colFirst"><code>float</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getMaxPreference--">getMaxPreference</a></span>()</code>&nbsp;</td>
</tr>
<tr id="i3" class="rowColor">
<td class="colFirst"><code>float</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getMinPreference--">getMinPreference</a></span>()</code>&nbsp;</td>
</tr>
<tr id="i4" class="altColor">
<td class="colFirst"><code>int</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getNumItems--">getNumItems</a></span>()</code>&nbsp;</td>
</tr>
<tr id="i5" class="rowColor">
<td class="colFirst"><code>int</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getNumUsers--">getNumUsers</a></span>()</code>&nbsp;</td>
</tr>
<tr id="i6" class="altColor">
<td class="colFirst"><code>int</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getNumUsersWithPreferenceFor-long-">getNumUsersWithPreferenceFor</a></span>(long&nbsp;itemID)</code>&nbsp;</td>
</tr>
<tr id="i7" class="rowColor">
<td class="colFirst"><code>int</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getNumUsersWithPreferenceFor-long-long-">getNumUsersWithPreferenceFor</a></span>(long&nbsp;itemID1,
long&nbsp;itemID2)</code>&nbsp;</td>
</tr>
<tr id="i8" class="altColor">
<td class="colFirst"><code><a href="../../../../../../org/apache/mahout/cf/taste/model/PreferenceArray.html" title="interface in org.apache.mahout.cf.taste.model">PreferenceArray</a></code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getPreferencesForItem-long-">getPreferencesForItem</a></span>(long&nbsp;itemID)</code>&nbsp;</td>
</tr>
<tr id="i9" class="rowColor">
<td class="colFirst"><code><a href="../../../../../../org/apache/mahout/cf/taste/model/PreferenceArray.html" title="interface in org.apache.mahout.cf.taste.model">PreferenceArray</a></code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getPreferencesFromUser-long-">getPreferencesFromUser</a></span>(long&nbsp;userID)</code>&nbsp;</td>
</tr>
<tr id="i10" class="altColor">
<td class="colFirst"><code><a href="http://docs.oracle.com/javase/7/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a></code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getPreferenceTime-long-long-">getPreferenceTime</a></span>(long&nbsp;userID,
long&nbsp;itemID)</code>
<div class="block">Retrieves the time at which a preference value from a user and item was set, if known.</div>
</td>
</tr>
<tr id="i11" class="rowColor">
<td class="colFirst"><code><a href="http://docs.oracle.com/javase/7/docs/api/java/lang/Float.html?is-external=true" title="class or interface in java.lang">Float</a></code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getPreferenceValue-long-long-">getPreferenceValue</a></span>(long&nbsp;userID,
long&nbsp;itemID)</code>
<div class="block">Retrieves the preference value for a single user and item.</div>
</td>
</tr>
<tr id="i12" class="altColor">
<td class="colFirst"><code><a href="../../../../../../org/apache/mahout/cf/taste/impl/common/LongPrimitiveIterator.html" title="interface in org.apache.mahout.cf.taste.impl.common">LongPrimitiveIterator</a></code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getUserIDs--">getUserIDs</a></span>()</code>&nbsp;</td>
</tr>
<tr id="i13" class="rowColor">
<td class="colFirst"><code>boolean</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#hasPreferenceValues--">hasPreferenceValues</a></span>()</code>&nbsp;</td>
</tr>
<tr id="i14" class="altColor">
<td class="colFirst"><code>void</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#removePreference-long-long-">removePreference</a></span>(long&nbsp;userID,
long&nbsp;itemID)</code>
<div class="block">
Removes a particular preference for a user.</div>
</td>
</tr>
<tr id="i15" class="rowColor">
<td class="colFirst"><code>void</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#setPreference-long-long-float-">setPreference</a></span>(long&nbsp;userID,
long&nbsp;itemID,
float&nbsp;value)</code>
<div class="block">
Sets a particular preference (item plus rating) for a user.</div>
</td>
</tr>
</table>
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<h3>Methods inherited from interface&nbsp;org.apache.mahout.cf.taste.common.<a href="../../../../../../org/apache/mahout/cf/taste/common/Refreshable.html" title="interface in org.apache.mahout.cf.taste.common">Refreshable</a></h3>
<code><a href="../../../../../../org/apache/mahout/cf/taste/common/Refreshable.html#refresh-java.util.Collection-">refresh</a></code></li>
</ul>
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<h3>Method Detail</h3>
<a name="getUserIDs--">
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<h4>getUserIDs</h4>
<pre><a href="../../../../../../org/apache/mahout/cf/taste/impl/common/LongPrimitiveIterator.html" title="interface in org.apache.mahout.cf.taste.impl.common">LongPrimitiveIterator</a>&nbsp;getUserIDs()
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<dl>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>all user IDs in the model, in order</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
</dl>
</li>
</ul>
<a name="getPreferencesFromUser-long-">
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<h4>getPreferencesFromUser</h4>
<pre><a href="../../../../../../org/apache/mahout/cf/taste/model/PreferenceArray.html" title="interface in org.apache.mahout.cf.taste.model">PreferenceArray</a>&nbsp;getPreferencesFromUser(long&nbsp;userID)
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>userID</code> - ID of user to get prefs for</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>user's preferences, ordered by item ID</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/NoSuchUserException.html" title="class in org.apache.mahout.cf.taste.common">NoSuchUserException</a></code> - if the user does not exist</dd>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
</dl>
</li>
</ul>
<a name="getItemIDsFromUser-long-">
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<ul class="blockList">
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<h4>getItemIDsFromUser</h4>
<pre><a href="../../../../../../org/apache/mahout/cf/taste/impl/common/FastIDSet.html" title="class in org.apache.mahout.cf.taste.impl.common">FastIDSet</a>&nbsp;getItemIDsFromUser(long&nbsp;userID)
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>userID</code> - ID of user to get prefs for</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>IDs of items user expresses a preference for</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/NoSuchUserException.html" title="class in org.apache.mahout.cf.taste.common">NoSuchUserException</a></code> - if the user does not exist</dd>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
</dl>
</li>
</ul>
<a name="getItemIDs--">
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<h4>getItemIDs</h4>
<pre><a href="../../../../../../org/apache/mahout/cf/taste/impl/common/LongPrimitiveIterator.html" title="interface in org.apache.mahout.cf.taste.impl.common">LongPrimitiveIterator</a>&nbsp;getItemIDs()
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<dl>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>a <a href="../../../../../../org/apache/mahout/cf/taste/impl/common/LongPrimitiveIterator.html" title="interface in org.apache.mahout.cf.taste.impl.common"><code>LongPrimitiveIterator</code></a> of all item IDs in the model, in order</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
</dl>
</li>
</ul>
<a name="getPreferencesForItem-long-">
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<ul class="blockList">
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<h4>getPreferencesForItem</h4>
<pre><a href="../../../../../../org/apache/mahout/cf/taste/model/PreferenceArray.html" title="interface in org.apache.mahout.cf.taste.model">PreferenceArray</a>&nbsp;getPreferencesForItem(long&nbsp;itemID)
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>itemID</code> - item ID</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>all existing <a href="../../../../../../org/apache/mahout/cf/taste/model/Preference.html" title="interface in org.apache.mahout.cf.taste.model"><code>Preference</code></a>s expressed for that item, ordered by user ID, as an array</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/NoSuchItemException.html" title="class in org.apache.mahout.cf.taste.common">NoSuchItemException</a></code> - if the item does not exist</dd>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
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</li>
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<h4>getPreferenceValue</h4>
<pre><a href="http://docs.oracle.com/javase/7/docs/api/java/lang/Float.html?is-external=true" title="class or interface in java.lang">Float</a>&nbsp;getPreferenceValue(long&nbsp;userID,
long&nbsp;itemID)
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<div class="block">Retrieves the preference value for a single user and item.</div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>userID</code> - user ID to get pref value from</dd>
<dd><code>itemID</code> - item ID to get pref value for</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>preference value from the given user for the given item or null if none exists</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/NoSuchUserException.html" title="class in org.apache.mahout.cf.taste.common">NoSuchUserException</a></code> - if the user does not exist</dd>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
</dl>
</li>
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<h4>getPreferenceTime</h4>
<pre><a href="http://docs.oracle.com/javase/7/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>&nbsp;getPreferenceTime(long&nbsp;userID,
long&nbsp;itemID)
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<div class="block">Retrieves the time at which a preference value from a user and item was set, if known.
Time is expressed in the usual way, as a number of milliseconds since the epoch.</div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>userID</code> - user ID for preference in question</dd>
<dd><code>itemID</code> - item ID for preference in question</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>time at which preference was set or null if no preference exists or its time is not known</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/NoSuchUserException.html" title="class in org.apache.mahout.cf.taste.common">NoSuchUserException</a></code> - if the user does not exist</dd>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
</dl>
</li>
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<a name="getNumItems--">
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<h4>getNumItems</h4>
<pre>int&nbsp;getNumItems()
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<dl>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>total number of items known to the model. This is generally the union of all items preferred by
at least one user but could include more.</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
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<h4>getNumUsers</h4>
<pre>int&nbsp;getNumUsers()
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<dl>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>total number of users known to the model.</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
</dl>
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</ul>
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<h4>getNumUsersWithPreferenceFor</h4>
<pre>int&nbsp;getNumUsersWithPreferenceFor(long&nbsp;itemID)
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>itemID</code> - item ID to check for</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>the number of users who have expressed a preference for the item</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
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<h4>getNumUsersWithPreferenceFor</h4>
<pre>int&nbsp;getNumUsersWithPreferenceFor(long&nbsp;itemID1,
long&nbsp;itemID2)
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>itemID1</code> - first item ID to check for</dd>
<dd><code>itemID2</code> - second item ID to check for</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>the number of users who have expressed a preference for the items</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
</dl>
</li>
</ul>
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<h4>setPreference</h4>
<pre>void&nbsp;setPreference(long&nbsp;userID,
long&nbsp;itemID,
float&nbsp;value)
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<div class="block"><p>
Sets a particular preference (item plus rating) for a user.
</p></div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>userID</code> - user to set preference for</dd>
<dd><code>itemID</code> - item to set preference for</dd>
<dd><code>value</code> - preference value</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/NoSuchItemException.html" title="class in org.apache.mahout.cf.taste.common">NoSuchItemException</a></code> - if the item does not exist</dd>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/NoSuchUserException.html" title="class in org.apache.mahout.cf.taste.common">NoSuchUserException</a></code> - if the user does not exist</dd>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
</dl>
</li>
</ul>
<a name="removePreference-long-long-">
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<h4>removePreference</h4>
<pre>void&nbsp;removePreference(long&nbsp;userID,
long&nbsp;itemID)
throws <a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></pre>
<div class="block"><p>
Removes a particular preference for a user.
</p></div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>userID</code> - user from which to remove preference</dd>
<dd><code>itemID</code> - item to remove preference for</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/NoSuchItemException.html" title="class in org.apache.mahout.cf.taste.common">NoSuchItemException</a></code> - if the item does not exist</dd>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/NoSuchUserException.html" title="class in org.apache.mahout.cf.taste.common">NoSuchUserException</a></code> - if the user does not exist</dd>
<dd><code><a href="../../../../../../org/apache/mahout/cf/taste/common/TasteException.html" title="class in org.apache.mahout.cf.taste.common">TasteException</a></code> - if an error occurs while accessing the data</dd>
</dl>
</li>
</ul>
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<h4>hasPreferenceValues</h4>
<pre>boolean&nbsp;hasPreferenceValues()</pre>
<dl>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>true if this implementation actually stores and returns distinct preference values;
that is, if it is not a 'boolean' DataModel</dd>
</dl>
</li>
</ul>
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<h4>getMaxPreference</h4>
<pre>float&nbsp;getMaxPreference()</pre>
<dl>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>the maximum preference value that is possible in the current problem domain being evaluated. For
example, if the domain is movie ratings on a scale of 1 to 5, this should be 5. While a
<a href="../../../../../../org/apache/mahout/cf/taste/recommender/Recommender.html" title="interface in org.apache.mahout.cf.taste.recommender"><code>Recommender</code></a> may estimate a preference value above 5.0, it
isn't "fair" to consider that the system is actually suggesting an impossible rating of, say, 5.4 stars.
In practice the application would cap this estimate to 5.0. Since evaluators evaluate
the difference between estimated and actual value, this at least prevents this effect from unfairly
penalizing a <a href="../../../../../../org/apache/mahout/cf/taste/recommender/Recommender.html" title="interface in org.apache.mahout.cf.taste.recommender"><code>Recommender</code></a></dd>
</dl>
</li>
</ul>
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<h4>getMinPreference</h4>
<pre>float&nbsp;getMinPreference()</pre>
<dl>
<dt><span class="seeLabel">See Also:</span></dt>
<dd><a href="../../../../../../org/apache/mahout/cf/taste/model/DataModel.html#getMaxPreference--"><code>getMaxPreference()</code></a></dd>
</dl>
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