将数据集分成相等的部分[所有可能的一半]

Question

我有一个数据集。我想把它分成相等的两部分。例如，如果有 10 列，我想获取两个 5 列的数据集。正如您所看到的，这可以通过

choose(10, 5) / 2 = 126

不同的方式来完成。我怎样才能确保每次分割都是不同的？

我已经走到这一步了。但是

sample()

函数不会给我我想要的东西。

# the data
data <- structure(list(V1 = c(0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 0, 0, 
0, 0, 1, 0, 1, 1, 1), V2 = c(0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 
0, 0, 1, 1, 1, 0, 1, 1, 1), V3 = c(0, 0, 1, 0, 0, 1, 0, 0, 1, 
0, 1, 1, 0, 0, 1, 1, 0, 1, 1, 0), V4 = c(0, 0, 1, 1, 0, 0, 0, 
1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0)), class = "data.frame", row.names = c(NA, 
-20L))

n1 <- ncol(data)
n2 <- ncol(data)/2
x1 <- colnames(data)

# the dataset can have an odd number of columns.
ifelse(n1%%2 == 0, MM <- sample(x1, n2), MM <- sample(x1, n2+1))

s1 <- data[MM]
s1

s2 <- data[!colnames(data) %in% MM]
s2

# s1 and s2 are completely different from each other.

mylist <- list(s1, s2)
mylist

我想将所有可能的一半合并到一个列表中。

Answer 1

您可以使用

gtools::combinations

获取所有组合并使用它来生成分割：

library(gtools)
split_data <- function(dat) {
  nc <- ncol(dat)
  ## get all combinations (TODO: add some logic to deal with nc being odd)
  sel <- combinations(nc, nc / 2L)
  ## however we need only half of them as the selection of the first half
  ## determines the other half
  sel_final <- sel[1:(nrow(sel) / 2L), ]
  apply(sel_final, 1L, function(set1) {
    set1_idx <- 1:ncol(dat) %in% set1
    set2_idx <- !set1_idx
    list(grp1 = dat[, set1_idx],
         grp2 = dat[, set2_idx])
  })
}

str(split_data(data))
# List of 3
#  $ :List of 2
#   ..$ grp1:'data.frame':        20 obs. of  2 variables:
#   .. ..$ V1: num [1:20] 0 1 0 1 1 1 1 1 1 0 ...
#   .. ..$ V2: num [1:20] 0 1 0 0 0 0 1 1 0 0 ...
#   ..$ grp2:'data.frame':        20 obs. of  2 variables:
#   .. ..$ V3: num [1:20] 0 0 1 0 0 1 0 0 1 0 ...
#   .. ..$ V4: num [1:20] 0 0 1 1 0 0 0 1 0 0 ...
#  $ :List of 2
#   ..$ grp1:'data.frame':        20 obs. of  2 variables:
#   .. ..$ V1: num [1:20] 0 1 0 1 1 1 1 1 1 0 ...
#   .. ..$ V3: num [1:20] 0 0 1 0 0 1 0 0 1 0 ...
#   ..$ grp2:'data.frame':        20 obs. of  2 variables:
#   .. ..$ V2: num [1:20] 0 1 0 0 0 0 1 1 0 0 ...
#   .. ..$ V4: num [1:20] 0 0 1 1 0 0 0 1 0 0 ...
#  $ :List of 2
#   ..$ grp1:'data.frame':        20 obs. of  2 variables:
#   .. ..$ V1: num [1:20] 0 1 0 1 1 1 1 1 1 0 ...
#   .. ..$ V4: num [1:20] 0 0 1 1 0 0 0 1 0 0 ...
#   ..$ grp2:'data.frame':        20 obs. of  2 variables:
#   .. ..$ V2: num [1:20] 0 1 0 0 0 0 1 1 0 0 ...
#   .. ..$ V3: num [1:20] 0 0 1 0 0 1 0 0 1 0 ...