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POHow to use the timestamp in mahout (taste)? (Using Java)
 

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  1. POHow to use the timestamp in mahout (taste)? (Using Java)
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    <p>I need to add timestamp(movielens dataset) into the slope-one algorithm to make it more accurate. </p> <p>I thought I should modify the source code(<a href="http://svn.apache.org/repos/asf/mahout/tags/mahout-0.4/core/src/main/java/org/apache/mahout/cf/taste/impl/recommender/slopeone/MemoryDiffStorage.java" rel="nofollow">MemoryDiffStorage.java</a> in mahout-core/...cf/taste/impl/recommender/slopeone), but I don't know how add the timestamp.</p> <p>Even though I found the definition <code>Long getPreferenceTime(long userID, long itemID)</code> in <a href="http://svn.apache.org/repos/asf/mahout/tags/mahout-0.4/core/src/main/java/org/apache/mahout/cf/taste/model/DataModel.java" rel="nofollow">DataModle.java</a>, I still have no idea about it.</p> <p>I should say I am new to Java and Mahout. So explain to me in detail please! Thanks~ :)</p> <p>Add modified code below:) Original code is in MemoryDiffStorage.java, I just plug some statements in. I wonder if I plug in wrong place,but I thought this is where it gets values.</p> <pre><code>private long processOneUser(long averageCount, long userID) throws TasteException { log.debug("Processing prefs for user {}", userID); // Save off prefs for the life of this loop iteration PreferenceArray userPreferences = dataModel.getPreferencesFromUser(userID); int length = userPreferences.length(); for (int i = 0; i &lt; length - 1; i++) { float prefAValue = userPreferences.getValue(i); long itemIDA = userPreferences.getItemID(i); long Timestamp = dataModel.getPreferenceTime(userID, itemIDA); long timestamp_max = 1046388675; long timestamp_min = 975042787; long t = (Timestamp - timestamp_min)/(timestamp_max - timestamp_min); prefAValue = prefAValue * t; FastByIDMap&lt;RunningAverage&gt; aMap = averageDiffs.get(itemIDA); if (aMap == null) { aMap = new FastByIDMap&lt;RunningAverage&gt;(); averageDiffs.put(itemIDA, aMap); } for (int j = i + 1; j &lt; length; j++) { // This is a performance-critical block long itemIDB = userPreferences.getItemID(j); RunningAverage average = aMap.get(itemIDB); if (average == null &amp;&amp; averageCount &lt; maxEntries) { average = buildRunningAverage(); aMap.put(itemIDB, average); averageCount++; } if (average != null) { average.addDatum(userPreferences.getValue(j) - prefAValue); } } </code></pre>
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    1. USSenchan Sue
    1. USSenchan Sue
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      1. POHow to use the timestamp in mahout (taste)? (Using Java)
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    1. COYou've found methods that provide the timestamp... what do you mean that you can't use them?
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      1. POHow to use the timestamp in mahout (taste)? (Using Java)
      1. USSean Owen
    2. CO@SeanOwen Thank you for your comment. I mean I don't know how to use it.(I'm not sure if my English could be understood by natives) I've modified the source codes but it made no change in results.
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      1. POHow to use the timestamp in mahout (taste)? (Using Java)
      1. USSenchan Sue
    3. COYou use it by getting timestamp information and using that in your algorithm. How you do that is up to you. The framework itself does not use timestamp.
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      1. POHow to use the timestamp in mahout (taste)? (Using Java)
      1. USSean Owen
 

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