[英]How to map a function on a nested Tibble in R when there are NA in nested column?
考慮這樣的 Tibble:
df <- tibble(station = c("station1","station2"), data = c(list(NA), list(tibble(timestamp = c("2001-01-01","2002-01-02", "2002-01-03"), value=c(1,2,3)))))
我現在想要 map function,就像嵌套小標題中時間戳列上的 lubridate::ymd() 一樣。 問題是我在 df-tibble 的父數據列中有 NA 值,需要留在那里。
有可行的解決方案嗎?
非常感謝你!
我用 mutate、mutate_if、map、map_if、else_if 嘗試了幾件事,但對我沒有任何作用。
另一種選擇是將map_if
與is.data.frame
一起使用:
library(tidyverse)
df <- tibble(
station = c("station1", "station2"),
data = c(list(NA), list(tibble(timestamp = c("2001-01-01", "2002-01-02", "2002-01-03"), value = c(1, 2, 3))))
)
df <- df |>
mutate(data = map_if(data, is.data.frame, ~ mutate(.x, timestamp = lubridate::ymd(timestamp))))
df$data
#> [[1]]
#> [1] NA
#>
#> [[2]]
#> # A tibble: 3 × 2
#> timestamp value
#> <date> <dbl>
#> 1 2001-01-01 1
#> 2 2002-01-02 2
#> 3 2002-01-03 3
您可以在映射 function 中使用條件語句:
df2 <- df %>%
mutate(data = map(data, function(x) {
if(is.data.frame(x)) mutate(x, timestamp = lubridate::ymd(timestamp))
else x
}))
df2
#> # A tibble: 2 x 2
#> station data
#> <chr> <list>
#> 1 station1 <lgl [1]>
#> 2 station2 <tibble [3 x 2]>
df2$data
#> [[1]]
#> [1] NA
#>
#> [[2]]
#> # A tibble: 3 x 2
#> timestamp value
#> <date> <dbl>
#> 1 2001-01-01 1
#> 2 2002-01-02 2
#> 3 2002-01-03 3
nest
/ unnest
的可能解決方案:
> df2 <- df %>% unnest(data) %>% mutate(timestamp = ymd(timestamp)) %>% nest(data = c(timestamp, value))
> df2
# A tibble: 2 × 2
station data
<chr> <list>
1 station1 <tibble [1 × 2]>
2 station2 <tibble [3 × 2]>
> df2$data
[[1]]
# A tibble: 1 × 2
timestamp value
<date> <dbl>
1 NA NA
[[2]]
# A tibble: 3 × 2
timestamp value
<date> <dbl>
1 2001-01-01 1
2 2002-01-02 2
3 2002-01-03 3
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