/// <summary>
/// 获取聚类结果的评价指标
/// </summary>
/// <param name="data">聚类结果</param>
/// <param name="K">类的个数</param>
/// <returns>结果的purity和gini</returns>
public static ValidationPair GetValidation(Dataset data, int K)
{
dataset = data.Data.ToArray();
nClusters = K;
ValidationPair result = new ValidationPair();
result.gini = GetGini();
result.purity = GetPurity();
return result;
}
/// <summary>
/// 执行kmeans聚类方法，生成K个类，重复执行repeat次选结果最好的
/// </summary>
/// <param name="K">聚类个数</param>
/// <param name="repeat">重复次数</param>
/// <returns>聚类结果的purity和gini指标</returns>
public ValidationPair Generate(int K, int repeat, PrintLogFunction PrintLog)
{
ValidationPair result = new ValidationPair();
for (int r = 0; r < repeat; r++)
{
PrintLog("正在执行第" + r.ToString() + "次kmeans聚类...");
#region 执行一次聚类
presentative = new DataType[K];
InitializePresentative(K);
double sumDist = 100;
bool isOver = false;
while (sumDist > convergence)
{
//对当前的代表进行聚类
isOver = true;
foreach (var data in dataset.Data)
{
double minDist = double.MaxValue;
int lableNow = 0;
for (int i = 0; i < K; i++)
{
double d = Matrix.Dist(data.features, presentative[i].features);
if (d < minDist)
{
minDist = d;
lableNow = i;
}
}
if (lableNow != data.label) isOver = false;
data.label = lableNow;
}
if (isOver == true) break;//若当前迭代未改变类，则结束
//生成新的代表
DataType[] newPresentative = new DataType[K];
for (int i = 0; i < K; i++)
{
int clusterCount = 0;
newPresentative[i] = new DataType(presentative[0].cntFeatures);
//新的代表取聚类中所有向量的平均值
foreach (var data in dataset.Data)
{
if (data.label != i) continue;
clusterCount++;
newPresentative[i].Add(data);
}
for (int j = 0; j < newPresentative[i].cntFeatures; j++) newPresentative[i].features[j] /= clusterCount;
}
//计算两次代表之间的平均距离
sumDist = 0;
for (int i = 0; i < K; i++)
{
sumDist += Matrix.Dist(presentative[i].features, newPresentative[i].features);
}
presentative = newPresentative;
sumDist /= K;
}
#endregion
#region 生成评价指标
ValidationPair v = ClusterValidater.GetValidation(dataset, K);
if (v.purity>=result.purity)
{
if (v.purity > result.purity) result = v;
else if (v.gini < result.gini) result = v;
}
#endregion
}
return result;
}
