R 函数，用于根据单行条件为分组数据赋值

Question

我想根据分组变量中的值创建一个新的数据列。

例如，给定以下数据集，如果第一个时间点的值为“蓝色”，我想将组的所有行分配为 TRUE 值。

这是我的数据集的示例：

group <- c("A","A", "A", "A", "B","B","B","B","C", "C", "C","C")
time <- c("t1","t2","t3","t4","t1","t2","t3","t4","t1","t2","t3","t4")
color <- c("blue", "red", "green", "yellow", "yellow","green","purple", "blue", "blue", "green", "yellow","red")
first_row_blue <- c(TRUE,TRUE,TRUE,TRUE,FALSE,FALSE,FALSE,FALSE,TRUE,TRUE,TRUE,TRUE)

df <- data.frame(group, time, color, first_row_blue)

df

最后一列是我希望数据具有的内容，但我不希望对其进行硬编码。

我试过这个：

df %>%
  group_by(group) %>% 
  mutate(all_blue = ifelse(time == "t1" & color == "blue", TRUE, FALSE))

但是，即使数据已分组，它也仅将 TRUE 值分配给第一行。 我是否缺少一个功能可以让我做我正在寻找的事情？

我还看到过一些帖子，用于执行某些操作，例如计算写入“蓝色”的次数，但是这不起作用，因为它出现在 t1 以外的时间。

预先感谢您的任何建议！

Answer 1

尝试

first

：

df %>% 
  group_by(group) %>% 
  mutate(x = first(color) == "blue")

Answer 2

library(tidyverse)

group <- c("A","A", "A", "A", "B","B","B","B","C", "C", "C","C")
time <- c("t1","t2","t3","t4","t1","t2","t3","t4","t1","t2","t3","t4")
color <- c("blue", "red", "green", "yellow", "yellow","green","purple", "blue", "blue", "green", "yellow","red")
first_row_blue <- c(TRUE,TRUE,TRUE,TRUE,FALSE,FALSE,FALSE,FALSE,TRUE,TRUE,TRUE,TRUE)

df <- data.frame(group, time, color, first_row_blue)

df %>%
  group_by(group) %>% 
  mutate(blue2 = ifelse(time == "t1" & color == "blue", TRUE, NA)) |> 
  fill(blue2) %>% 
  mutate(blue2 = replace_na(blue2, FALSE))
#> # A tibble: 12 × 5
#> # Groups:   group [3]
#>    group time  color  first_row_blue blue2
#>    <chr> <chr> <chr>  <lgl>          <lgl>
#>  1 A     t1    blue   TRUE           TRUE 
#>  2 A     t2    red    TRUE           TRUE 
#>  3 A     t3    green  TRUE           TRUE 
#>  4 A     t4    yellow TRUE           TRUE 
#>  5 B     t1    yellow FALSE          FALSE
#>  6 B     t2    green  FALSE          FALSE
#>  7 B     t3    purple FALSE          FALSE
#>  8 B     t4    blue   FALSE          FALSE
#>  9 C     t1    blue   TRUE           TRUE 
#> 10 C     t2    green  TRUE           TRUE 
#> 11 C     t3    yellow TRUE           TRUE 
#> 12 C     t4    red    TRUE           TRUE

^{创建于 2024-05-06，使用 reprex v2.1.0}