使用 fill = NA 将向量作为列添加到 data.frame

Question

我有一个长度为 3 的向量 (my_vector)。

我想将此向量作为新列绑定到现有的 data.frame (my_df)。

但是，data.frame 有 4 行。因此，在第 4 行，新列值（或 my_df[4,3]）应该是 NA。

我怎样才能做到这一点？

当我执行my_df$new_column <- my_vector 时，我收到以下错误消息： 替换有 3 行，数据有 4 行

---

这里是my_df（包括4行）：

> 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)
)

还有my_vector（长度为3）：

> dput(my_vector)

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

Answer 1

我们创建一个NA 列，然后根据向量的长度分配“my_vector”。这里seq_along(my_vector)返回1:3，因此前3个元素被替换为'my_vector'值

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

---

或者如果我们使用length<-在末尾填充NA，这可以一步完成

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

-输出

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

您可以将 my_vector 中的值作为子集，其长度与 my_df 相同。

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

data.table 选项

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

给予

> 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>