r - 如何从 lapply-attack 中保存我的矩阵列表的结构？

Question

我想将整数矩阵列表转换为数字。我知道lapply对内部结构不友好，但是有没有lapply-solution？

mtList = list(matrix(sample(1:10),nrow=5),
              matrix(sample(1:21),nrow=7))
str(mtList)

# This works, and I could wrap it in a for loop
mtList[[1]][] = as.numeric(mtList[[1]])
mtList[[2]][] = as.numeric(mtList[[2]])
str(mtList)

# But how to use lapply here? Note that the internal
# matrix structure is flattened
mtList1 = lapply(mtList,function(x)x[] = as.numeric(x))
str(mtList1)

Answer 1

您必须在您的 lapply 主力函数中返回值:

mtList1 = lapply(mtList,function(x) {
  x[] = as.numeric(x)
  x
})

str(mtList1)
# List of 2
#  $ : num [1:5, 1:2] 1 7 6 3 9 10 5 2 8 4
#  $ : num [1:7, 1:3] 21 3 15 14 6 4 18 17 9 8 ...