在 R 编程中生成 xCm 的所有组合 – combn()函数

R 语言中的combn()函数用于生成一次取m的x元素的所有组合。

Syntax: combn(x, m)

Parameters:
x: total number of elements taken
r: number of elements taken at a time out of “x” elements

示例 1：

# R program to illustrate
# combn function
  
# Calling the combn() function
combn(5, 3)
combn(6, 5)
combn(2, 2)

输出：

[, 1] [, 2] [, 3] [, 4] [, 5] [, 6] [, 7] [, 8] [, 9] [, 10]
[1, ]    1    1    1    1    1    1    2    2    2     3
[2, ]    2    2    2    3    3    4    3    3    4     4
[3, ]    3    4    5    4    5    5    4    5    5     5

     [, 1] [, 2] [, 3] [, 4] [, 5] [, 6]
[1, ]    1    1    1    1    1    2
[2, ]    2    2    2    2    3    3
[3, ]    3    3    3    4    4    4
[4, ]    4    4    5    5    5    5
[5, ]    5    6    6    6    6    6

     [, 1]
[1, ]    1
[2, ]    2

示例 2：

# R program to illustrate
# combn function
  
# Calling the combn() function
combn(LETTERS[1: 4], 2)
combn(LETTERS[2: 6], 3)

输出：

[, 1] [, 2] [, 3] [, 4] [, 5] [, 6]
[1, ] "A"  "A"  "A"  "B"  "B"  "C" 
[2, ] "B"  "C"  "D"  "C"  "D"  "D" 

     [, 1] [, 2] [, 3] [, 4] [, 5] [, 6] [, 7] [, 8] [, 9] [, 10]
[1, ] "B"  "B"  "B"  "B"  "B"  "B"  "C"  "C"  "C"  "D"  
[2, ] "C"  "C"  "C"  "D"  "D"  "E"  "D"  "D"  "E"  "E"  
[3, ] "D"  "E"  "F"  "E"  "F"  "F"  "E"  "F"  "F"  "F"