Accessing Element of a Split String in R

How to use strsplit() to access elements in an R list?

A "tidyverse" approach similar to suggestion in comments by @GavinSimpson:

library(purrr)
library(stringr)

x <- rep("stringA, stringB", 10)

str_split(x, ", ") %>% map_chr(`[`, 2)
#>  [1] "stringB" "stringB" "stringB" "stringB" "stringB" "stringB" "stringB"
#>  [8] "stringB" "stringB" "stringB"

• str_split() acts like strsplit().
• map_chr() acts like lapply(), but also converts resulting list to a character vector.

For your problem, substitute x for list1$field2

First entry from string split

If you need to extract the first (or nth) entry from each split, use:

word <- c('apple-orange-strawberry','chocolate')

sapply(strsplit(word,"-"), `[`, 1)
#[1] "apple"     "chocolate"

Or faster and more explictly:

vapply(strsplit(word,"-"), `[`, 1, FUN.VALUE=character(1))
#[1] "apple"     "chocolate"

Both bits of code will cope well with selecting whichever value in the split list, and will deal with cases that are outside the range:

vapply(strsplit(word,"-"), `[`, 2, FUN.VALUE=character(1))
#[1] "orange" NA  

Access n-th element after string splitting

1) data.frame Convert to a data frame and then it is easy to pick off a column or subset of columns:

DF <- read.table(text = string, sep = ",", as.is = TRUE)

DF[[1]]
## [1] "A" "B" "A"

DF[[3]]
## [1] "some text"       "some other text" "yet another one"

DF[-1]
##   V2              V3  V4
## 1  1       some text 200
## 2  2 some other text 300
## 3  3 yet another one 100

DF[2:3]
##   V2              V3
## 1  1       some text
## 2  2 some other text
## 3  3 yet another one

2) data.table::tranpose The data.table package has a function to tranpose lists so that if stringt is the tranposed list then stringt[[3]] is the vector of third fields, say, in a similar way to (1). Even more compact is data.table's tstrsplit mentioned by @Henrik below or the same package's fread mentioned by @akrun below.

library(data.table)

stringt <- transpose(strsplit(string, ","))

# or
stringt <- tstrsplit(string, ",")

stringt[[1]]
## [1] "A" "B" "A"

stringt[[3]]
## [1] "some text"       "some other text" "yet another one"

stringt[-1]
## [[1]]
## [1] "1" "2" "3"
##
## [[2]]
## [1] "some text"       "some other text" "yet another one"
##
## [[3]]
## [1] "200" "300" "100"

stringt[2:3]
## [[1]]
## [1] "1" "2" "3"
##
## [[2]]
## [1] "some text"       "some other text" "yet another one"

purrr also has a transpose function but

library(purrr)
transpose(strsplit(string, ","))

produces a list of lists rather than a list of character vectors.

How to get the first element of a strsplit in R

try this :

variable = unlist(strsplit('AAAAAA.BBBB', '\\.'))[1]

R get last element from str_split

As the comment on your question suggests, this is suitable for gsub:

gsub("^.*_", "", string_thing)

I'd recommend you take note of the following cases as well.

string_thing <- c("I_AM_STRING", "I_AM_ALSO_STRING_THING", "AM I ONE", "STRING_")
gsub("^.*_", "", string_thing)
[1] "STRING"   "THING"    "AM I ONE" ""  

Getting the second item after using str_split() in R

I think you're looking for str_replace (or sub in base R)

x %>% mutate(words = str_replace(question, "^\\d+\\.", ""))
#              question             words
#1   01. I like my job.    I like my job.
#2 02. I like my house.  I like my house.
#3   03. I like my car.    I like my car.

Explanation:

1. ^ is the left string anchor
2. \\d+\\. matches one or more digit(s) followed by a full stop

You can use str_split in the following way

x %>% mutate(words = paste0(map_chr(str_split(question, "\\."), 2), "."))

giving the same result.

How to split an element in a character vector and insert it as a new element?

You are on the right path with strsplit, just use unlist to get a vector.

> unlist(strsplit(string, ","))
[1] "Eric"    "John"    "Dora"    "Michael" " James"  "Susan" 

R split string into elements, sort and recombine

We need a second *apply to loop through elements of x.

test[, (cols) := (lapply(.SD, function(x) {
   #browser()
   sapply(x, function(y) paste(sort(trimws(strsplit(y, ',')[[1]])), collapse=','))
})), .SDcols = cols]

> test
              col1                col2
1:   cow,horse,pig aardvark,fish,moose
2: frog,orange,pig  aardvark,elk,whale

strsplit(x, ',')[[1]] used the first element from each column, as you can see below

Browse[1]> strsplit(x, ',')
[[1]]
[1] "cow"    " pig"   " horse"

[[2]]
[1] "orange" " pig"   " frog"

Browse[1]> strsplit(x, ',')[[1]]
[1] "cow"    " pig"   " horse"

accessing individual values split by str_split in R, finding the last one?

Taken from: Find file name from full file path

basename("C:/some_dir/a")
> [1]  "a"

dirname("C:/some_dir/a")
>[1] "C:/some_dir"

Although I think the above approach is much better, you can also use the str_split approach - which I really only mention to show how to select the last elements from a list using lapply.

example <- c("C:/some_dir/a","C:/some_dir/sdfs/a","C:/some_dir/asdf/asdf/a")
example.split <- strsplit(example,"/")
files <- unlist(lapply(example.split, tail , 1 ))

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