how to split and filter a string?-CodePudding

Consider this character

mystring <- "this, this and this, and this, and this."

I want to split on , or and but I want to get rid of the empty strings. I am puzzled by the fact that my solution below does not work

splitting works OK

> str_split(mystring, regex(',|and'))
[[1]]
[1] "this"   " this " " this"  " "      " this"  " "      " this."

filtering does not work

> str_split(mystring, regex(',|and')) %>% purrr::keep(., function(x) x!= '')
Error: Predicate functions must return a single `TRUE` or `FALSE`, not a logical vector of length 7
Run `rlang::last_error()` to see where the error occurred.

What is the issue here? Thanks!

CodePudding user response：

If we return only blank ("") instead of spaces (" "), then we can make use of nzchar

library(purrr)
library(stringr)
str_split(mystring, regex('\\s*,\\s*|\\s*and\\s*'))[[1]]  %>%
    keep(nzchar)
[1] "this"  "this"  "this"  "this"  "this."

If we are using the OP's code, use trimws before the keep step

str_split(mystring, regex(',|and')) %>%
    pluck(1) %>%
    trimws %>%
    keep(nzchar) 
[1] "this"  "this"  "this"  "this"  "this."

In the OP's code, the keep didn't work because the object from str_split is a list and the element was not extracted. Thus, when we apply the function, it returns multiple TRUE/FALSE for the single list element whereas keep expects a single TRUE/FALSE. Here, we are plucking the list element. In the first solution, extraction was done by [[1]]