本文轉(zhuǎn)載自：https://www.cnblogs.com/hider/p/10019220.html

總結(jié)

組合數(shù)：choose(n,k) —— 從n個(gè)中選出k個(gè)

階乘：factorial(k) —— k!

排列數(shù)：choose(n,k) * factorial(k)

冪：^

余數(shù)：%%

整數(shù)商：%/%

列出所有組合數(shù)矩陣：combn(x,n)

t(combn(x,n)) 轉(zhuǎn)置

二、例子

choose(5,3) # 10
factorial(5) # 120
choose(5,3)*factorial(3) # 60
2^10 # 1024
10 %% 3 # 1
10 %/% 3 # 3

x <- 1:5
n <-3
combn(x,n)
/*
[,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
*/

x <- 1:5
n <-3
combn(x,n)
/*
[,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
*/