Example usage for org.apache.mahout.cf.taste.model PreferenceArray sortByItem

Introduction

In this page you can find the example usage for org.apache.mahout.cf.taste.model PreferenceArray sortByItem.

Prototype

void sortByItem();

Source Link

Document

Sorts underlying array by item ID, ascending.

Usage

From source file:norbert.mynemo.core.recommendation.similarity.OriginalSpearmanCorrelationSimilarity.java

License:Apache License

@Override
public double userSimilarity(final long userId1, final long userId2) throws TasteException {

    final PreferenceArray xPrefs = dataModel.getPreferencesFromUser(userId1).clone();
    final PreferenceArray yPrefs = dataModel.getPreferencesFromUser(userId2).clone();

    final int numCommonPref = numCommonPreferences(userId1, userId2);
    if (numCommonPref < 2) {
        return Double.NaN;
    }/*from   w ww  .  java2  s  .c  o m*/

    xPrefs.sortByItem();
    yPrefs.sortByItem();

    final double[] xCommonPrefs = new double[numCommonPref];
    final double[] yCommonPrefs = new double[numCommonPref];

    // copy the common preferences
    int xNewPrefIndex = 0;
    for (int xIndex = 0; xIndex < xPrefs.length(); xIndex++) {
        if (yPrefs.hasPrefWithItemID(xPrefs.getItemID(xIndex))) {
            xCommonPrefs[xNewPrefIndex] = xPrefs.getValue(xIndex);
            xNewPrefIndex++;
        }
    }
    int yNewPrefIndex = 0;
    for (int yIndex = 0; yIndex < yPrefs.length(); yIndex++) {
        if (xPrefs.hasPrefWithItemID(yPrefs.getItemID(yIndex))) {
            yCommonPrefs[yNewPrefIndex] = yPrefs.getValue(yIndex);
            yNewPrefIndex++;
        }
    }

    return SPEARMAN_CORRELATION.correlation(xCommonPrefs, yCommonPrefs);
}

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