在r中连接多个数据帧 a1

使用下一个代码，您可以获得类似于所需的

数据帧的内容：

a1 <- data.frame(id=c(1,1,1,1,2,2,2,3,3),
                var=c("6402","1","1","3","6406","6406","2","1","1"))
b1 <- data.frame(var=c("6402","6406"),
                txt=c("A","B"))
n1 <- data.frame(id=c(1,2,3))


desired <- data.frame(id=c(1,2,3),
                      txt=c("A","B",NA))

输出：

#Code
merge(n1,merge(a1,b1)[,-1],all.x = T)[!duplicated(merge(n1,merge(a1,b1)[,-1],all.x = T)[,'id']),]

id-txt
11A
2 B
4  3 
这里是一个使用嵌套的
合并的基本R选项

  id  txt
1  1    A
2  2    B
4  3 <NA>

给

merge(n1,
  merge(unique(a1),
    b1,
    by = "var",
    all.y = TRUE
  ),
  by = "id",
  all = TRUE
)[c("id", "txt")]

id-txt
11A
2 B
3  3 
我们可以使用
tidyverse

  id  txt
1  1    A
2  2    B
3  3 <NA>

答案中除了data.table之外的所有R的风格-如果能发布所有选项就好了。
library(dplyr)
distinct(a1) %>%
   left_join(b1, by = 'var') %>% 
   full_join(n1) %>%
   group_by(id) %>%
   summarise(txt = first(txt))
# A tibble: 3 x 2
#     id txt  
#  <dbl> <chr>
#1     1 A    
#2     2 B    
#3     3 <NA> 

unique(setDT(a1))[b1,  txt := txt, on = .(var)][n1, .SD[1],
      on = .(id), by = .EACHI][, var := NULL][]