Handling empty strings in string detection

Question

I would like to use str_detect and not convert "" to another string pattern. Is there an easy way to deal with empty string patterns "" which right now generates a warning. I would like this to produce TRUE, FALSE, FALSE, FALSE, FALSE

library( tidyverse )
str_detect('matt', c( "matt","joe","liz","", NA))

just do it in the other way around str_detect(c( "matt","joe","liz","", NA), 'matt') if you really want the last element from output to be FALSE instead of NA, your input should be c( "matt","joe","liz","", "NA") , note NA inside `"`` — Jilber Urbina
– Jilber Urbina, Commented Mar 28, 2019 at 14:49

Community · Accepted Answer · 2020-06-20 09:12:55Z

9

We can use

library(stringr)
library(tidyr)
str_detect(replace_na(v1, ''), 'matt')
#[1]  TRUE FALSE FALSE FALSE FALSE

If the match is not for a substring, then %in% would be useful

v1 %in% 'matt'
#[1]  TRUE FALSE FALSE FALSE FALSE

data

v1 <- c( "matt","joe","liz","", NA)

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Mar 28, 2019 at 14:44

akrun

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Comments

tomasu · Accepted Answer · 2019-03-28 14:58:20Z

6

If you're not tied to str_detect() perhaps try grepl()?

grepl("matt", c( "matt","joe","liz","", NA))

#[1]  TRUE FALSE FALSE FALSE FALSE

answered Mar 28, 2019 at 14:58

tomasu

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1 Comment

flashton Over a year ago

I prefer this one because it handles NAs better (str_detect won't return any rows that contain NAs)

Rui Barradas · Accepted Answer · 2019-03-28 14:55:43Z

2

Here is a way with package stringi the base of package stringr.

x <- c( "matt","joe","liz","", NA)
stringi::stri_detect_regex(x, 'matt') & !is.na(x)
#[1]  TRUE FALSE FALSE FALSE FALSE

The NA value must be tested, if not stri_detect_* will return NA.

answered Mar 28, 2019 at 14:55

Rui Barradas

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Comments

Rushabh Patel · Accepted Answer · 2019-03-28 15:05:57Z

2

You could also do-

v1 <- c( "matt","joe","liz","", NA)
sapply(v1, identical, "matt")

Output-

 matt   joe   liz        <NA> 
 TRUE FALSE FALSE FALSE FALSE

edited Mar 28, 2019 at 15:05

answered Mar 28, 2019 at 15:00

Rushabh Patel

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