如何在矩阵中保存变量索引以计算出现次数

    for (i in 1:10){

      z1<-rnorm(1000,0,1)
      z2<-rnorm(1000,0,1)
      z3<-rnorm(1000,0,1)
      z4<-rnorm(1000,0,1)
      z5<-rnorm(1000,0,1)
      z6<-rnorm(1000,0,1)
      z7<-rnorm(1000,0,1)

      X<-cbind(z1,z2,z3,z4,z5,z6)

      Z<-apply(X,2,mean)
       test[i]<-which(Z>0.01, arr.ind=TRUE)

    }
    for (i in 1:10){

      z1<-rnorm(1000,0,1)