在Java中,處理K-means算法中的不平衡數(shù)據(jù)可以通過以下幾種方法:
重采樣(Resampling):
為K-means算法添加權(quán)重:
使用其他聚類算法:
以下是一個(gè)簡單的Java示例,展示了如何使用SMOTE算法進(jìn)行過采樣:
public class SMOTE {
public static void main(String[] args) {
// 加載數(shù)據(jù)集
// 假設(shè)data是一個(gè)包含樣本特征和標(biāo)簽的二維數(shù)組
double[][] data = ...;
// 設(shè)置過采樣參數(shù)
int k = 5; // 最近鄰居的數(shù)量
double ratio = 1.0; // 用于控制過采樣的倍數(shù)
// 應(yīng)用SMOTE算法
double[][] oversampledData = oversample(data, k, ratio);
}
public static double[][] oversample(double[][] data, int k, double ratio) {
int n = data.length;
int[] labels = new int[n];
for (int i = 0; i < n; i++) {
labels[i] = (int) data[i][data.length - 1];
}
int[][] newSamples = new int[n * (int) (ratio + 1)][data[0].length];
int index = 0;
for (int i = 0; i < n; i++) {
if (labels[i] == 0) {
continue;
}
List<Integer> neighbors = getNeighbors(data, i, k);
for (int j : neighbors) {
newSamples[index++] = data[j];
}
for (int j = 1; j < (int) (ratio + 1); j++) {
int randomIndex = new Random().nextInt(n);
while (labels[randomIndex] == 0) {
randomIndex = new Random().nextInt(n);
}
newSamples[index++] = data[randomIndex];
}
}
return Arrays.copyOf(newSamples, index);
}
private static List<Integer> getNeighbors(double[][] data, int index, int k) {
int[] vector = data[index];
List<Integer> neighbors = new ArrayList<>();
for (int i = 0; i < data.length; i++) {
if (i == index) {
continue;
}
double distance = euclideanDistance(vector, data[i]);
if (distance <= k) {
neighbors.add(i);
}
}
return neighbors;
}
private static double euclideanDistance(double[] a, double[] b) {
double sum = 0;
for (int i = 0; i < a.length; i++) {
sum += Math.pow(a[i] - b[i], 2);
}
return Math.sqrt(sum);
}
}
請注意,這個(gè)示例僅用于演示目的,實(shí)際應(yīng)用中可能需要根據(jù)具體情況進(jìn)行調(diào)整。