contextapi/code/Common/Classifier.java

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package uk.co.md87.android.common;

import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

/**
 *
 * @author chris
 */
public class Classifier {

    private final Set<Map.Entry<Float[], String>> model;

    public Classifier(final Set<Entry<Float[], String>> model) {
        this.model = model;
    }

    public String classify(final float[] data) {
        float oddTotal = 0, evenTotal = 0;
        float oddMin = Float.MAX_VALUE, oddMax = Float.MIN_VALUE;
        float evenMin = Float.MAX_VALUE, evenMax = Float.MIN_VALUE;

        for (int i = 0; i < 128; i++) {
            evenTotal += data[i * 2];
            oddTotal += data[i * 2 + 1];

            evenMin = Math.min(evenMin, data[i * 2]);
            oddMin = Math.min(oddMin, data[i * 2 + 1]);

            evenMax = Math.max(evenMax, data[i * 2]);
            oddMax = Math.max(oddMax, data[i * 2 + 1]);
        }

        final float[] points = {
            Math.abs(evenTotal / 128),
            Math.abs(oddTotal / 128),
            evenMax - evenMin,
            oddMax - oddMin
        };

        float bestDistance = Float.MAX_VALUE;
        String bestActivity = "UNCLASSIFIED/UNKNOWN";

        for (Map.Entry<Float[], String> entry : model) {
            float distance = 0;

            for (int i = 0; i < points.length; i++) {
                distance += Math.pow(points[i] - entry.getKey()[i], 2);
            }

            if (distance < bestDistance) {
                bestDistance = distance;
                bestActivity = entry.getValue();
            }
        }

        return bestActivity;
    }
}