r - str_replace 模式是 ""给出 "Error in mutate_impl(.data, dots) : Evaluation error: Not implemented."

Question

我在 df 中有一个功能，其中一些缺失值仅显示为“”。

unique(page_my_df$Type)
[1] "list"              "narrative" "how to"            "news feature"     
[5] "diary"     ""                  "interview" 

我想用“未知”替换“”的所有实例。

page_my_df <- page_my_df %>% 
  mutate(Type = str_replace(.$Type, "", "unknown"),
         Voice = str_replace(.$Voice, "", "unknown"))

Error in mutate_impl(.data, dots) : Evaluation error: Not implemented.

阅读一些文档 here ，特别是在模式下:

Match character, word, line and sentence boundaries with boundary(). An empty pattern, "", is equivalent to boundary("character").

所以我试过:

page_my_df <- page_my_df %>% 
  mutate(Type = str_replace(.$Type, boundary(""), "unknown"),
         Voice = str_replace(.$Voice, boundary(""), "unknown"))

然后给出:

Error in mutate_impl(.data, dots) : Evaluation error: 'arg' should be one of “character”, “line_break”, “sentence”, “word”.

如何在 dplyr::mutate() 中用“unknown”替换空字符串？

Answer 1

这是一种方法:

library(tidyverse)
library(stringr)

z <- c( "list",  "narrative",  "how to",  "news feature",  
"diary",  "" , "interview" )

data.frame(element = 1:length(z), Type = z) %>%
  mutate(Type = str_replace(Type, "^$", "unknown"))
#output
  element         Type
1       1         list
2       2    narrative
3       3       how to
4       4 news feature
5       5        diary
6       6      unknown
7       7    interview

也无需使用 .$ 引用 mutate 调用中的数据框

^ 和美元符号 $ 是元字符，分别匹配行首和行尾的空字符串。