r - 在保留组的同时填充数值变量

Question

[编辑以反射(reflect)更好的例子]

假设我有一个这样的数据框:

df <- data.frame(x = c("A","A","B", "B"), year = c(2001,2004,2002,2005))

> df
  x year
1 A 2001
2 A 2004
3 B 2002
4 B 2005

如何增加 year在保留的同时减 1 x ?我要填写 year所以顺序是这样的:

  x year
1 A 2001
2 A 2002
3 A 2003
4 A 2004
5 B 2002
6 B 2003
7 B 2004
8 B 2005

任何人都可以推荐这样做的好方法吗？

@useR 推荐这种方法:

> data.frame(year = min(df$year):max(df$year)) %>%
   full_join(df) %>%
   fill(x) 
Joining, by = "year"
  year x
1 2001 A
2 2002 B
3 2003 B
4 2004 A
5 2005 B

但是，这与所需的输出不匹配。

Answer 1

使用基础 R(在 zoo 的帮助下):

full_df = data.frame(year = min(df$year):max(df$year))
df = merge(df, full_df, all = TRUE)
df = df[order(df$year), ]
df$x = zoo::na.locf(df$x)
df
#   year x
# 1 2001 A
# 2 2002 A
# 3 2003 A
# 4 2004 B
# 5 2005 B
# 6 2006 B
# 7 2007 C

使用“tidyverse”

df <- data.frame(x = LETTERS[1:3], year = c(2001,2004,2007))
library(dplyr)
library(tidyr)
df = df %>% mutate(year = factor(year, levels = min(year):max(year))) %>%
    complete(year) %>%
    fill(x) %>%
    mutate(year = as.numeric(as.character(year)))
df
# # A tibble: 7 x 2
#    year      x
#   <dbl> <fctr>
# 1  2001      A
# 2  2002      A
# 3  2003      A
# 4  2004      B
# 5  2005      B
# 6  2006      B
# 7  2007      C