完成函数function label =kmeans_clustering(data, num)，其中输入变量data为N行m列，每一行为一个数据点，num为聚类数目；输出变量label为N行1列，表示对应的数据点属于哪一类。-Complete function function label = kmeans_clustering (data, num), wherein the input variable data to N rows by m columns, each act a data point, num is the number of clusters　output variable label for the N rows 1, indicates that the corresponding data point belongs which category.