使用 fill = NA 将向量作为列添加到 data.frame

Question

I have a vector of length 3 ( my_vector ).

I want to bind this vector to an existing data.frame ( my_df ) as a new column.

However, the data.frame has 4 rows. Thus, in the 4th row, the new column value (or my_df[4,3] ) should be NA .

How can I achieve this?

When I do my_df$new_column <- my_vector , I get the following error message: replacement has 3 rows, data has 4

---

Here is my_df (comprising 4 rows):

> dput(my_df)

structure(list(
      person = c("Oleg", "Yurii", "Igor", "Mikhail"),
      role = structure(c(1L, 2L, 2L, 3L), class = "factor", .Label = c("EDITOR-IN-CHIEF", "DEPUTY EDITORS-IN-CHIEF", "Coordinating Editor"))),
      class = "data.frame", row.names = c(NA,  -4L)
)

And my_vector (of length 3):

> dput(my_vector)

c("Lomonosov University", "Russian Academy of Sciences", "Institute of Acoustics, Moscow, Russia")

Answer 1

We create a NA column and then assign the 'my_vector' based on the length of the vector. Here seq_along(my_vector) return 1:3 , thus the first 3 elements are replaced with 'my_vector' values

my_df$new_column <- NA_character_
my_df$new_column[seq_along(my_vector)] <- my_vector

---

Or this can be done in a single step if we pad NA at the end by making use of length<-

my_df$new_column <-  `length<-`(my_vector, nrow(my_df))

-output

my_df
#   person                    role                             new_column
#1    Oleg         EDITOR-IN-CHIEF                   Lomonosov University
#2   Yurii DEPUTY EDITORS-IN-CHIEF            Russian Academy of Sciences
#3    Igor DEPUTY EDITORS-IN-CHIEF Institute of Acoustics, Moscow, Russia
#4 Mikhail     Coordinating Editor                                   <NA>

Answer 2

You could subset the values from my_vector which has same length as my_df .

my_df$new_column <- my_vector[seq_len(nrow(my_df))]
my_df

#   person                    role                             new_column
#1    Oleg         EDITOR-IN-CHIEF                   Lomonosov University
#2   Yurii DEPUTY EDITORS-IN-CHIEF            Russian Academy of Sciences
#3    Igor DEPUTY EDITORS-IN-CHIEF Institute of Acoustics, Moscow, Russia
#4 Mikhail     Coordinating Editor                                   <NA>

Answer 3

A data.table option

setDT(my_df)[, new := NA][, new := replace(new, seq_along(my_vector), my_vector)]

gives

> my_df
    person                    role                                    new
1:    Oleg         EDITOR-IN-CHIEF                   Lomonosov University
2:   Yurii DEPUTY EDITORS-IN-CHIEF            Russian Academy of Sciences
3:    Igor DEPUTY EDITORS-IN-CHIEF Institute of Acoustics, Moscow, Russia
4: Mikhail     Coordinating Editor                                   <NA>