R中有列表的警告消息和没有列表的罚款，为什么？

假设我有这个矩阵：

Matrix <- c(5, 2, 3, 1, 4,
                 0, 2, 3, 4, 1,
                 0, 0, 3, 4, 1,
                 0, 0, 0, 4, 1,
                 0, 0, 0, 0, 1)
      Matrix <- matrix(Matrix, 5, 5)
fam <- list()
for (i in 1:3){
fam[i] <- array(0, dim = dim(Matrix))
}

但是，如果没有列表，它可以正常工作

> fam
     [,1] [,2] [,3] [,4] [,5]
[1,]    0    0    0    0    0
[2,]    0    0    0    0    0
[3,]    0    0    0    0    0
[4,]    0    0    0    0    0
[5,]    0    0    0    0    0

---

哪里是我的错误？？？

而不是

fam[i]

尝试

fam[[i]]

[[选择列表中的单个元素]
[[ selects a single element of a list

for (i in 1:3){
  fam[[i]] <- array(0, dim = dim(Matrix))
}

（我在1:3中）{
fam[[i]]
> fam
     [,1] [,2] [,3] [,4] [,5]
[1,]    0    0    0    0    0
[2,]    0    0    0    0    0
[3,]    0    0    0    0    0
[4,]    0    0    0    0    0
[5,]    0    0    0    0    0

[[ selects a single element of a list

for (i in 1:3){
  fam[[i]] <- array(0, dim = dim(Matrix))
}