R根据另一个表中的变量列表保留和排序变量

Question

这被认为是一项简单的任务，而且微不足道，但我无法让它发挥作用。我想创建一个新表，使用与另一个表相同的顺序。假设我的当前数据具有与过去数据相同的 5 个变量，但顺序不同。我希望当前数据具有相同的结构。我尝试使用旧数据中的列名列表并使用 R data.table 来排列变量，但是正如您从示例中看到的那样，新数据是列表/字符或带有空数据的 data.table。有什么建议？谢谢!

> str(new)
Classes ‘data.table’ and 'data.frame':  2 obs. of  7 variables:
 $ id: int  1 2
 $ x1: int  0 1
 $ x4: int  1 0
 $ x5: int  1 0
 $ x2: int  0 0
 $ x3: int  1 0
 $ x6: int  0 1
 - attr(*, ".internal.selfref")=<externalptr> 

> str(old)
Classes ‘data.table’ and 'data.frame':  2 obs. of  6 variables:
 $ id: int  1 2
 $ x1: int  1 0
 $ x2: int  1 0
 $ x3: int  1 0
 $ x4: int  0 0
 $ x5: int  1 0
 - attr(*, ".internal.selfref")=<externalptr> 

 namelist <- list(names(old))
newlist <- new[,c(namelist)] # using data.table to order the variables
 newlist <- new[,unlist(namelist)] # newlist is character instead of data.table

newlist <- new[,c(namelist)] # data.table but not expected data.
 class(newlist)
[1] "data.table" "data.frame"
> str(newlist)
Classes ‘data.table’ and 'data.frame':  6 obs. of  1 variable:
 $ V1: chr  "id" "x1" "x2" "x3" ...
 - attr(*, ".internal.selfref")=<externalptr> 

Answer 1

使用更方便setcolorder通过将 'new' 中的唯一列与 intersect 连接起来按该顺序输入列名

nm1 <- setdiff(names(new), names(old))
nm2 <- intersect(names(new), names(old))
setcolorder(new,  gtools::mixedsort(c(nm1, nm2)))
new
#   id x1 x2 x3 x4 x5 x6
#1:  1  0  0  1  1  1  0
#2:  2  1  0  0  0  0  1

或者另一种选择是

setcolorder(new, names(rbindlist(list(old, new), fill = TRUE)))

或与 union

setcolorder(new, setdiff(union(names(old), names(new)), 
                 setdiff(names(old), names(new))))

数据

new <- data.table(id = 1:2, x1 = 0:1, x4 = 1:0, x5 = 1:0, x2 = 0, x3 = 1:0, x6 = 0:1) 
old <- data.table(id = 1:2, x1 = 1:0, x2 = 1:0, x3 = 1:0, x4 = 0, x5 = 1:0)