r - left_join 在具有不同列名的 for 循环中

Question

我有一个名为 a 的 data.frame其结构类似于:-

a <- data.frame(X1=c("A", "B", "C", "A", "C", "D"),
                X2=c("B", "C", "D", "A", "B", "A"),
                X3=c("C", "D", "A", "B", "A", "B")
               )

我还有另一套是:-

b <- data.frame(Xn=c("A", "B", "C", "D"),
                Feature=c("some", "more", "what", "why"))

我要添加所有 Features从集合 b设置 a ，使得 X1 , X2和 X3在集合中具有相应的特征列 a .换句话说，集合 a 中的列变得:-

colnames(a) <- c("X1", "X2", "X3", "Features1", "Features2", "Features3")

如何在 for 循环中使用 left_join 来做到这一点？

Answer 1

在基础 R 中，我们可以 unlist a数据框和 match它与 b$Xn获取对应的Feature值(value)。我们可以cbind将此数据框转换为原始数据框以获得最终答案。

temp <- a
temp[] <- b$Feature[match(unlist(temp), b$Xn)]
names(temp) <- paste0('Feature', seq_along(temp))
cbind(a, temp)

#  X1 X2 X3 Feature1 Feature2 Feature3
#1  A  B  C     some     more     what
#2  B  C  D     more     what      why
#3  C  D  A     what      why     some
#4  A  A  B     some     some     more
#5  C  B  A     what     more     some
#6  D  A  B      why     some     more

在 tidyverse ，我们可以得到长格式的数据，加入数据并把它恢复成宽格式。

library(dplyr)
library(tidyr)

a %>%
  mutate(row = row_number()) %>%
  pivot_longer(cols = -row) %>%
  left_join(b, by = c('value' = 'Xn'))  %>%
  select(-value) %>%
  pivot_wider(names_from = name, values_from = Feature) %>%
  select(-row) %>%
  rename_all(~paste0('Feature', seq_along(.))) %>%
  bind_cols(a, .)