在数据框中添加一行，从向量 R 中获取值

Question

我有一个这样的df

df <- data.frame (id = c(123,123,456), w1= c("abc","fgh","kit"), w2 = c("eat","drink","ty"))

   id  w1    w2
1 123 abc   eat
2 123 fgh drink
3 456 kit    ty

和一个向量

vec <- c('value1', 'value2').

当有精确对应时，我想将这些值添加到df中。我想获得的最终df是这样的：

   id  w1    w2 new_col
1 123 abc   eat  value1
2 123 abc   eat  value2
3 123 fgh drink  no correspondance
4 456 kit    ty  no correspondance

我试过这个代码

for (i in 1:length(df$id)) { ## for iterating each row 
  if (df$w2[i] == 'eat') {
    df$new_col[i] <- vec ### how to? Here I need to replace both 'value1' and 'value2' copying the row 
  }
}

有人可以给我一些建议吗？提前致谢！

Answer 1

使用tidyr库：

> library(tidyr)
> df[1, 'new_col'] <- toString(vec)
> df %>% separate_rows(new_col)
# A tibble: 4 x 4
     id w1    w2    new_col
  <dbl> <chr> <chr> <chr>  
1   123 abc   eat   value1 
2   123 abc   eat   value2 
3   123 fgh   drink <NA>   
4   456 kit   ty    <NA>   
>

编辑：

> library(tidyr)
> df[1, 'new_col'] <- toString(vec)
> df %>% %>% filter(new_col %in% c('value1', 'value2')) %>% separate_rows(new_col) %>% bind_rows(filter(df, !new_col %in% c('value1', 'value2')))

# A tibble: 4 x 4
     id w1    w2    new_col
  <dbl> <chr> <chr> <chr>  
1   123 abc   eat   value1 
2   123 abc   eat   value2 
3   123 fgh   drink <NA>   
4   456 kit   ty    <NA>   
>

Answer 2

您可以将列表列添加到数据框中，然后使用 tidyr::unnest 将它们作为单独的行。

inds <- df$w2 == "eat"
df$new_col[!inds] <- 'no correspondance'
df$new_col[inds] <- list(vec)
tidyr::unnest(df, new_col)

#     id w1    w2    new_col          
#  <dbl> <chr> <chr> <chr>            
#1   123 abc   eat   value1           
#2   123 abc   eat   value2           
#3   123 fgh   drink no correspondance
#4   456 kit   ty    no correspondance

Answer 3

使用 tidyverse，我们可以用 case_when 和 return 创建一个逻辑条件 list 列，然后执行 unnesting list列

library(dplyr)
library(tidyr)
df %>% 
   mutate(new_col = case_when(w2 == 'eat' ~ list(vec), 
           TRUE ~ list('no correspondance'))) %>% 
   unnest(new_col)
# A tibble: 4 × 4
     id w1    w2    new_col          
  <dbl> <chr> <chr> <chr>            
1   123 abc   eat   value1           
2   123 abc   eat   value2           
3   123 fgh   drink no correspondance
4   456 kit   ty    no correspondance

在数据框中添加一行，从向量 R 中获取值

Add a row in a dataframe taking values from a vector R

r

dataframe

rbind