CODEWITHSUNDEEP
rdplyrstringr
MatzeKnop
MatzeKnop

Reputation: 193

str_extract_all: return all patterns found in string concatenated as vector

I want to extract everything but a pattern and return this concetenated in a string.

I tried to combine str_extract_all together with sapply and cat

x = c("a_1","a_20","a_40","a_30","a_28")
data <- tibble(age = x)


# extracting just the first pattern is easy
data %>% 
  mutate(age_new = str_extract(age,"[^a_]"))
# combining str_extract_all and sapply doesnt work
data %>% 
  mutate(age_new = sapply(str_extract_all(x,"[^a_]"),function(x) cat(x,sep="")))


class(str_extract_all(x,"[^a_]"))
sapply(str_extract_all(x,"[^a_]"),function(x) cat(x,sep=""))

Returns NULL instead of concatenated patterns

Upvotes: 10

Views: 4205

Answers (2)

John F
John F

Reputation: 317

Here is a non tidyverse solution, just using stringr.

apply(str_extract_all(column,regex_command,simplify = TRUE),1,paste,collapse="")

'simplify' = TRUE changed str_extract_all to output a matrix, and apply iterates over the matrix. I got the idea from https://stackoverflow.com/a/4213674/8427463

Example: extract all 'r' in rownames(mtcar) and concatenate as a vector

library(stringr)
apply(str_extract_all(rownames(mtcars),"r",simplify = TRUE),1,paste,collapse="")

Upvotes: 2

akrun
akrun

Reputation: 887571

Instead of cat, we can use paste. Also, with tidyverse, can make use of map and str_c (in place of paste - from stringr)

library(tidyverse)
data %>% 
  mutate(age_new = map_chr(str_extract_all(x, "[^a_]+"), ~ str_c(.x, collapse="")))

using `OP's code

data %>%
    mutate(age_new = sapply(str_extract_all(x,"[^a_]"),
               function(x) paste(x,collapse="")))

If the intention is to get the numbers

library(readr)
data %>%
     mutate(age_new = parse_number(x))

Upvotes: 16

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