r - 查找每列数据集列表的唯一级别

Question

我有一个包含 18 个数据集的列表，每个数据集都有一些列，我如何编写一个循环来通过列索引查找相交，并返回列索引列表。

df1 <- data.frame(id = c(1:5), loc = c("a","b","c","a","b"))
df2 <- data.frame(id = c(3:7), ta = c("c","b","d","a","b"))
df3 <- data.frame(id = c(1:5), az = c("d","a","e","d","b"))

df <- list(df1, df2, df3)
df <- lapply(df, function(i) lapply(i, function(j) as.character(j)))

intersect(df[[1]][1], df[[2]][1], df[[3]][1])
intersect(df[[1]][2], df[[2]][2], df[[3]][2])

标签： rlist

Answer 1

tidyverse，我们可以使用map/reduce

library(purrr)
library(dplyr)
map(df, pull, 1) %>% 
      reduce(intersect)
#[1] 3 4 5

或者作为一个函数

f1 <- function(lstA, ind) {
          map(lstA, pull, ind) %>%
             reduce(intersect)
 }


f1(df, 1)
#[1] 3 4 5
f1(df, 2)
#[1] "a" "b"