lpa标签传播算法解说及代码实现

package lpa;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class LPA {

	public static float sigma = 1;
	public static int tag_num = 2;
	
	public static void main(String[] args) {
		
		float[][] data = {
				{1,1},
				{1,2},
				{2,1},
				{2,2},
				{4,4},
				{6,6},
				{6,7},
				{7,6},
				{7,7}
		};
		
		Map<Integer, Integer> tag_map = new HashMap<Integer, Integer>();
		tag_map.put(1, 1);
		tag_map.put(6, 0);
		
		float[][] weight = new float[data.length][data.length];
		
		for(int i = 0; i < weight.length; i++) {
			float sum = 0f;
			for(int j = 0; j < weight[i].length; j++) {
				weight[i][j] = (float) Math.exp( - distance(data[i], data[j]) / Math.pow(sigma, 2));
				sum += weight[i][j];
			}
			for(int j = 0; j < weight[i].length; j++) {
				weight[i][j] /= sum;
			}
		}
		
		System.out.println("=============");
		for(int i = 0; i < weight.length; i++) {
			System.out.println(Arrays.toString(weight[i]));
		}
		System.out.println("=============");
		
		float[][] tag_matrix = new float[data.length][tag_num];
		for(int i = 0; i < tag_matrix.length; i++) {
			if(tag_map.get(i) != null) {
				tag_matrix[i][tag_map.get(i)] = 1;
			} else {
				float sum = 0;
				for(int j = 0; j < tag_matrix[i].length; j++) {
					tag_matrix[i][j] = (float) Math.random();
					sum += tag_matrix[i][j];
				}
				for(int j = 0; j < tag_matrix[i].length; j++) {
					tag_matrix[i][j] /= sum;
				}
			}
		}
		
		for(int it = 0; it < 100; it++) {
			for(int i = 0; i < tag_matrix.length; i++) {
				if(tag_map.get(i) != null) {
					continue;
				}
				float all_sum = 0;
				for(int j = 0; j < tag_matrix[i].length; j++) {
					float sum = 0;
					for(int k = 0; k < weight.length; k++) {
						sum += weight[i][k] * tag_matrix[k][j];
					}
					tag_matrix[i][j] = sum;
					all_sum += sum;
				}
				for(int j = 0; j < tag_matrix[i].length; j++) {
					tag_matrix[i][j] /= all_sum;
				}
			}
			System.out.println("=============");
			for(int i = 0; i < tag_matrix.length; i++) {
				System.out.println(Arrays.toString(tag_matrix[i]));
			}
			System.out.println("=============");
		}
	}
	
	public static float distance(float[] a, float[] b) {
		
		float dis = 0;
		for(int i = 0; i < a.length; i++) {
			dis = (float) Math.pow(b[i] - a[i], 2);
		}
		return dis;
	}
}