I am in R and would like to extract a two digit number 38y from the following string:
"/Users/files/folder/file_number_23a_version_38y_Control.txt"
I know that _Control always comes after the 38y and that 38y is preceded by an underscore. How can I use strsplit or other R commands to extract the 38y?
You could use
regmatches(x, regexpr("[^_]+(?=_Control)", x, perl = TRUE))
# [1] "38y"
or equivalently
stringr::str_extract(x, "[^_]+(?=_Control)")
# [1] "38y"
Using gsub.
gsub('.*_(.*)_Control.*', '\\1', x)
# [1] "38y"
See demo with detailed explanation.
A possible solution:
library(stringr)
text <- "/Users/files/folder/file_number_23a_version_38y_Control.txt"
str_extract(text, "(?<=_)\\d+\\D(?=_Control)")
#> [1] "38y"
You can find an explanation of the regex part at:
https://regex101.com/r/PQSZHX/1
Related
Is there an R function to get only the part of a string before the 2nd capital character appears?
For example:
Example <- "MonkeysDogsCats"
Expected output should be:
"Monkeys"
Maybe something like
stringr::str_extract("MonkeysDogsCats", "[A-Z][a-z]*")
#[1] "Monkeys"
Here is an alternative approach:
Here we first put a space before all uppercase and then extract the first word:
library(stringr)
word(gsub("([a-z])([A-Z])","\\1 \\2", Example), 1)
[1] "Monkeys"
A base solution with sub():
x <- "MonkeysDogsCats"
sub("(?<=[a-z])[A-Z].*", "", x, perl = TRUE)
# [1] "Monkeys"
Another way using stringr::word():
stringr::word(x, 1, sep = "(?=[A-Z])\\B")
# [1] "Monkeys"
If the goal is strictly to capture any string before the 2nd capital character, one might want pick a solution it'll also work with all types of strings including numbers and special characters.
strings <- c("MonkeysDogsCats",
"M4DogsCats",
"M?DogsCats")
stringr::str_remove(strings, "(?<=.)[A-Z].*")
Output:
[1] "Monkeys" "M4" "M?"
It depends on what you want to allow to match. You can for example match an uppercase char [A-Z] optionally followed by any character that is not an uppercase character [^A-Z]*
If you don't want to allow whitespace chars, you can exclude them [^A-Z\\s]*
library(stringr)
str_extract("MonkeysDogsCats", "[A-Z][^A-Z]*")
Output
[1] "Monkeys"
R demo
If there should be an uppercase character following, and there are only lowercase characters allowed:
str <- "MonkeysDogsCats"
regmatches(str, regexpr("[A-Z][a-z]*(?=[A-Z])", str, perl = TRUE))
Output
[1] "Monkeys"
R demo
text <- c('d__Viruses|f__Closteroviridae|g__Closterovirus|s__Citrus_tristeza_virus',
'd__Viruses|o__Tymovirales|f__Alphaflexiviridae|g__Mandarivirus|s__Citrus_yellow_vein_clearing_virus',
'd__Viruses|o__Ortervirales|f__Retroviridae|s__Columba_palumbus_retrovirus')
I have tried but failed:
str_extract(text, pattern = 'f.*\\|')
How can I get
f__Closteroviridae
f__Alphaflexiviridae
f__Retroviridae
Any help will be high appreciated!
Make the regex non-greedy and since you don't want "|" in final output use positive lookahead.
stringr::str_extract(text, 'f.*?(?=\\|)')
#[1] "f__Closteroviridae" "f__Alphaflexiviridae" "f__Retroviridae"
In base R, we can use sub :
sub('.*(f_.*?)\\|.*', '\\1', text)
#[1] "f__Closteroviridae" "f__Alphaflexiviridae" "f__Retroviridae"
For a base R solution, I would use regmatches along with gregexpr:
m <- gregexpr("\\bf__[^|]+", text)
as.character(regmatches(text, m))
[1] "f__Closteroviridae" "f__Alphaflexiviridae" "f__Retroviridae"
The advantage of using gregexpr as above is that should an input contain more than one f__ matching term, we could also capture it. For example:
x <- 'd__Viruses|f__Closteroviridae|g__Closterovirus|f__some_virus'
m <- gregexpr("\\bf__[^|]+", x)
regmatches(x, m)[[1]]
[1] "f__Closteroviridae" "f__some_virus"
Data:
text <- c('d__Viruses|f__Closteroviridae|g__Closterovirus|s__Citrus_tristeza_virus',
'd__Viruses|o__Tymovirales|f__Alphaflexiviridae|g__Mandarivirus|s__Citrus_yellow_vein_clearing_virus',
'd__Viruses|o__Ortervirales|f__Retroviridae|s__Columba_palumbus_retrovirus')
I am trying to count the number of dots in a character string.
I have tried to use str_count but it gives me the number of letters of the string instead.
ex_str <- "This.is.a.string"
str_count(ex_str, '.')
nchar(ex_str)
. is a special regex symbol, so you need to escape it:
str_count(ex_str, '\\.')
# [1] 3
Using just base R you could do:
nchar(gsub("[^.]", "", ex_str))
Using stringi:
stri_count_fixed(ex_str, '.')
Another base R solution could be:
length(grepRaw(".", ex_str, fixed = TRUE, all = TRUE))
[1] 3
You may also use the base function gregexpr:
sum(gregexpr(".", ex_str, fixed=TRUE)[[1]] > 0)
[1] 3
You can use stringr::str_count with a fixed(...) argument to avoid treating it as a regular expression:
str_count(ex_str, fixed('.'))
See the online R demo:
library(stringr)
ex_str <- "This.is.a.string"
str_count(ex_str, fixed('.'))
## => [1] 3
I'd like to extract everything after "-" in vector of strings in R.
For example in :
test = c("Pierre-Pomme","Jean-Poire","Michel-Fraise")
I'd like to get
c("Pomme","Poire","Fraise")
Thanks !
With str_extract. \\b is a zero-length token that matches a word-boundary. This includes any non-word characters:
library(stringr)
str_extract(test, '\\b\\w+$')
# [1] "Pomme" "Poire" "Fraise"
We can also use a back reference with sub. \\1 refers to string matched by the first capture group (.+), which is any character one or more times following a - at the end:
sub('.+-(.+)', '\\1', test)
# [1] "Pomme" "Poire" "Fraise"
This also works with str_replace if that is already loaded:
library(stringr)
str_replace(test, '.+-(.+)', '\\1')
# [1] "Pomme" "Poire" "Fraise"
Third option would be using strsplit and extract the second word from each element of the list (similar to word from #akrun's answer):
sapply(strsplit(test, '-'), `[`, 2)
# [1] "Pomme" "Poire" "Fraise"
stringr also has str_split variant to this:
str_split(test, '-', simplify = TRUE)[,2]
# [1] "Pomme" "Poire" "Fraise"
We can use sub to match characters (.*) until the - and in the replacement specify ""
sub(".*-", "", test)
Or another option is word
library(stringr)
word(test, 2, sep="-")
I think the other answers might be what you're looking for, but if you don't want to lose the original context you can try something like this:
library(tidyverse)
tibble(test) %>%
separate(test, c("first", "last"), remove = F)
This will return a dataframe containing the original strings plus components, which might be more useful down the road:
# A tibble: 3 x 3
test first last
<chr> <chr> <chr>
1 Pierre-Pomme Pierre Pomme
2 Jean-Poire Jean Poire
3 Michel-Fraise Michel Fraise
For some reason the responses here didn't work for my particular string. I found this response more helpful (i.e., using Stringr's lookbehind function): stringr str_extract capture group capturing everything.
I have this variable
x= "379_exp_mirror1.csv"
I need to extract the number ("379") at the beggining (which doesn't always have 3 characters), i.e. everything before the first "". And then I need to extract everything between the second "" and the ".", in this case "mirror1".
I have tried several combinations with sub and gsub with no success, can anyone give me some indications please?
Thank you
You can use regular expression. For your problem ^(?<Number>[0-9]*)_.* do the job
1/ Test your regular expression with this website : http://derekslager.com/blog/posts/2007/09/a-better-dotnet-regular-expression-tester.ashx
Or you can split string with underscore and then try parse (int.TryParse). I think the second is better but if you want to be a regular expression master try the first method
You can use sub to extract the substrings:
x <- "379_exp_mirror1.csv"
sub("_.*", "", x)
# [1] "379"
sub("^(?:.*_){2}(.*?)\\..*", "\\1", x)
# [1] "mirror1"
Another approach with gregexpr:
regmatches(x, gregexpr("^.*?(?=_)|(?<=_)[^_]*?(?=\\.)", x, perl = TRUE))[[1]]
# [1] "379" "mirror1"
May be you can try:
library(stringr)
x <- "379_exp_mirror1.csv"
str_extract_all(x, perl('^[0-9]+(?=_)|[[:alnum:]]+(?=\\.)'))[[1]]
#[1] "379" "mirror1"
Or
strsplit(x, "[._]")[[1]][c(T,F)]
#[1] "379" "mirror1"
Or
scan(text=gsub("[.]","_", x),what="",sep="_")[c(T,F)]
#Read 4 items
#[1] "379" "mirror1"