查找vars的唯一组合，如果找到唯一的组合，则创建一个新var。

Question

我以这个dataframe作为玩具例子

aski = data.frame(A = c("x","y","z","x","z","z"),
                  B = c("a","b","c","a","b","c"))

现在我想检查A和B的每个唯一组合，如果这是一个唯一的组合，我想在数据中创建一个新变量并每次递增(例如r1，r2，.)发现了一种独特的梳子。

输出数据，如下所示

aski2 = data.frame(A = c("x","y","z","x","z","z"),
                   B = c("a","b","c","a","b","c"),
                   output = c("r1","r2","r3","r1","r4","r3"))

Answer 1

试试这个：

aski2 <- data.frame(A = c("x","y","z","x","z","z"),
                    B = c("a","b","c","a","b","c"))
ref <- do.call(paste, aski2)
aski2$output <- paste("r", as.numeric(factor(ref, levels = unique(ref))),
                      sep = "")
aski2

Answer 2

另一个选项是使用group_indices；Group列A和B，它为每个组生成一个唯一的id (参见?group_indices)：

aski2 <- data.frame(A = c("x","y","z","x","z","z"), 
                    B = c("a","b","c","a","b","c"), 
                    C = c("s","v","g","v","g","d"))

aski2 %>% mutate(output = sprintf("r%s", group_indices(., A, B)))

#  A B C output
#1 x a s     r1
#2 y b v     r2
#3 z c g     r4
#4 x a v     r1
#5 z b g     r3
#6 z c d     r4

Answer 3

一种选择是.GRP

library(data.table)
setDT(aski2)[, output := paste0("r", .GRP), .(A, B)]