如何将函数startsWith应用于几种模式？ [复制]

Question

我有一个数据框。我想为创建依赖于其他列的列编写条件。这里是：

tab <- tibble::tribble(
  ~dataset_id,  ~type,
     "Site4H",      268,
     "Site4D",      479,
     "SIte8H",      345,
     "Site8D",      567,
     "Site8K",      507
  )
library(dplyr)
tab %>%
  mutate(state = case_when(
    endsWith(dataset_id, "H") ~ "healthy",
    endsWith(dataset_id, "D") ~ "disease",
    TRUE                      ~ NA_character_
  ))

Answer 1

您可以将正则表达式与 rebus 包一起用于您的任务

library(dplyr)
library(rebus)
library(stringi)

# look for a string ending with H or K
pattern <- or("H", "K") %R% END

# gives you true if pattern is found else false (you can negate that with ! in fron of stringi
tab %>% 
  dplyr::mutate(state = stringi::stri_detect_regex(dataset_id, pattern))

  dataset_id bacteria state
  <chr>         <int> <lgl>
1 Site4H          268 TRUE 
2 Site4D          479 FALSE
3 SIte8H          345 TRUE 
4 Site8D          567 FALSE
5 Site8K          567 TRUE 

Answer 2

你可以使用grepl/str_detect来匹配模式。

要匹配“H”或“K”，您可以这样写：

library(dplyr)

tab %>%
  mutate(state = case_when(
    grepl('H|K', dataset_id) ~ "healthy",
    endsWith(dataset_id, "D") ~ "disease",
    TRUE                      ~ NA_character_
  ))

#   dataset_id bacteria state  
#  <chr>         <int> <chr>  
#1 Site4H          268 healthy
#2 Site4D          479 disease
#3 SIte8H          345 healthy
#4 Site8D          567 disease
#5 Site8K          567 healthy