R 在相似元素的数据集上循环

我有以下数据集，我想使用允许所有可能组合的循环策略（即“setA、setB、setC、setD”；“setA、setB、setC”；“setA、setB、setC”；“setA、setB”、“setB、setC、setD”；“setC、setD”；“setC、setD”等）比较它们所包含元素的相似性

数据集：

setA <- c("dog", "cat", "cow", "sheep", "dunkey")

setB <- c("fox", "cat", "cow", "snake")

setC <- c("dog", "cat", "cow", "sheep", "dunkey", "fox", "python")

setD <- c("dog", "cat", "lion", "sheep", "elephant", "fox")

setA这里是一个来自a的函数，用于获取所有交点

## Build intersections, 'out' accumulates the result
intersects <- function(sets, out=NULL) {
    if (length(sets) < 2) return ( out )                               # return result
    len <- seq(length(sets))
    if (missing(out)) out <- list()                                    # initialize accumulator
    for (idx in split((inds <- combn(length(sets), 2)), col(inds))) {  # 2-way combinations
        ii <- len > idx[2] & !(len %in% idx)                           # indices to keep for next intersect
        out[[(n <- paste(names(sets[idx]), collapse="."))]] <- intersect(sets[[idx[1]]], sets[[idx[2]]])
        out <- intersects(append(out[n], sets[ii]), out=out)
    }
    out
}

## Put the sets in a list
sets <- mget(paste0("set", toupper(letters[1:4])))

intersects(sets)
# $setA.setB
# [1] "cat" "cow"
# 
# $setA.setB.setC
# [1] "cat" "cow"
# 
# $setA.setB.setC.setD
# [1] "cat"
# 
# $setA.setB.setD
# [1] "cat"
# 
# $setC.setD
# [1] "dog"   "cat"   "sheep" "fox"  
# 
# $setA.setC
# [1] "dog"    "cat"    "cow"    "sheep"  "dunkey"
# 
# $setA.setC.setD
# [1] "dog"   "cat"   "sheep"
# 
# $setA.setD
# [1] "dog"   "cat"   "sheep"
# 
# $setB.setC
# [1] "fox" "cat" "cow"
# 
# $setB.setC.setD
# [1] "fox" "cat"
# 
# $setB.setD
# [1] "fox" "cat"

##构建交点，“out”累积结果
什么是期望的输出？太好了！正是我想要的。谢谢nongkrong，代码为我工作。非常感谢。
## Build intersections, 'out' accumulates the result
intersects <- function(sets, out=NULL) {
    if (length(sets) < 2) return ( out )                               # return result
    len <- seq(length(sets))
    if (missing(out)) out <- list()                                    # initialize accumulator
    for (idx in split((inds <- combn(length(sets), 2)), col(inds))) {  # 2-way combinations
        ii <- len > idx[2] & !(len %in% idx)                           # indices to keep for next intersect
        out[[(n <- paste(names(sets[idx]), collapse="."))]] <- intersect(sets[[idx[1]]], sets[[idx[2]]])
        out <- intersects(append(out[n], sets[ii]), out=out)
    }
    out
}

## Put the sets in a list
sets <- mget(paste0("set", toupper(letters[1:4])))

intersects(sets)
# $setA.setB
# [1] "cat" "cow"
# 
# $setA.setB.setC
# [1] "cat" "cow"
# 
# $setA.setB.setC.setD
# [1] "cat"
# 
# $setA.setB.setD
# [1] "cat"
# 
# $setC.setD
# [1] "dog"   "cat"   "sheep" "fox"  
# 
# $setA.setC
# [1] "dog"    "cat"    "cow"    "sheep"  "dunkey"
# 
# $setA.setC.setD
# [1] "dog"   "cat"   "sheep"
# 
# $setA.setD
# [1] "dog"   "cat"   "sheep"
# 
# $setB.setC
# [1] "fox" "cat" "cow"
# 
# $setB.setC.setD
# [1] "fox" "cat"
# 
# $setB.setD
# [1] "fox" "cat"