(R)如何删除在指定列中具有NULL值的所有行?

Question

我试图从我的数据帧tsLyrics中删除lyrics列的NULL值的每一行。我试过了

tsLyrics <- filter(tsLyrics, lyrics == NULL)

但是，我得到以下错误:

Error in `filter()`:
! Problem while computing `..1 = lyrics == NULL`.
x Input `..1` must be of size 338 or 1, not size 0.

我也试着把我的语法改成:

tsLyrics <- filter(tsLyrics, is.null(lyrics))

然而，当我这样做时，我得到一个空数据帧。我应该如何去除这些NULL?

在适用的情况下，lyrics列中的每个条目要么是列表，要么是NULL

数据例子

structure(list(track_name = c("Run (feat. Ed Sheeran) (Taylor’s Version) (From The Vault)", 
"The Very First Night (Taylor's Version) (From The Vault)", "All Too Well (10 Minute Version) (Taylor's Version) (From The Vault)", 
"State Of Grace (Taylor's Version)", "Red (Taylor's Version)"
), lyrics = list(structure(list(), .Names = character(0), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -1L)), structure(list(), .Names = character(0), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -1L)), structure(list(), .Names = character(0), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -1L)), structure(list(), .Names = character(0), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -1L)), NULL)), row.names = c(NA, 
-5L), class = c("tbl_df", "tbl", "data.frame"))

Answer 1

您可以使用sapply使用is.null函数对列进行映射

df <- structure(list(track_name = c("Run (feat. Ed Sheeran) (Taylor’s Version) (From The Vault)", 
"The Very First Night (Taylor's Version) (From The Vault)", "All Too Well (10 Minute Version) (Taylor's Version) (From The Vault)", 
"State Of Grace (Taylor's Version)", "Red (Taylor's Version)"
), lyrics = list(structure(list(), .Names = character(0), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -1L)), structure(list(), .Names = character(0), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -1L)), structure(list(), .Names = character(0), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -1L)), structure(list(), .Names = character(0), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -1L)), NULL)), row.names = c(NA, 
-5L), class = c("tbl_df", "tbl", "data.frame"))
library(dplyr, warn.conflicts = FALSE)
df
#> # A tibble: 5 × 2
#>   track_name                                                           lyrics  
#>   <chr>                                                                <list>  
#> 1 Run (feat. Ed Sheeran) (Taylor’s Version) (From The Vault)           <tibble>
#> 2 The Very First Night (Taylor's Version) (From The Vault)             <tibble>
#> 3 All Too Well (10 Minute Version) (Taylor's Version) (From The Vault) <tibble>
#> 4 State Of Grace (Taylor's Version)                                    <tibble>
#> 5 Red (Taylor's Version)                                               <NULL>
df %>% 
filter(!sapply(lyrics, is.null))
#> # A tibble: 4 × 2
#>   track_name                                                           lyrics  
#>   <chr>                                                                <list>  
#> 1 Run (feat. Ed Sheeran) (Taylor’s Version) (From The Vault)           <tibble>
#> 2 The Very First Night (Taylor's Version) (From The Vault)             <tibble>
#> 3 All Too Well (10 Minute Version) (Taylor's Version) (From The Vault) <tibble>
#> 4 State Of Grace (Taylor's Version)                                    <tibble>

^{在2022-05-04由reprex包(v2.0.1)创建}