R language-string processing functions, string functions

R language-string processing functions, string functions
Nchar

Function for retrieving the number of characters
Different from nchar, length is the length of the orientation.

# Nchar indicates the number of characters in the string. nchar ("abcd") [1] 4 # length indicates the number of elements in the vector. length ("abcd ") [1] 1 length (c ("hello", "world") [1] 2

Paste and paste0

String Bonding Function
When no Delimiter is specified for paste, the default Delimiter is a space.
Paste0 is blank by default when no Delimiter is specified

# Paste ("Hello", "world") [1] "Hello world" # No space paste0 ("Hello", "world") is separated by spaces by default ") [1] "Helloworld" # specify the delimiter paste ("abc", "efg", "hijk", sep = "-") [1] "abc-efg-hijk" # connect each element of the vector to paste0 ("A", sep = "") [1] "A1" "A2" A3 "" A4 "" A5 "" A6 "# collapse parameter: after each element operation, connect every element of the vector to paste0 ("A", sep = "", collapse = "-") [1] "A1-A2-A3-A4-A5-A6"

Substr

String truncation Function

substr(x = "hello", start = 1, stop = 2)[1] "he"

Strsplit

String delimiter to generate a list

strsplit("abc", split = "")[[1]][1] "a" "b" "c"

If you want to use this function for a vector, pay attention to it.

# Divide each element of a vector and obtain the unlist (lapply (X = c ("abc", "bcd", "dfafadf") of the first element after the split "), FUN = function (x) {return (strsplit (x, split = "") [[1] [1])}) [1] "a" "B" "d"

Gsub and sub

String replacement
Gsub replaces all matched
Replace the first matched sub

# Replace B with Bgsub (pattern = "B", replacement = "B", x = "baby") [1] "BaBy" gsub (pattern = "B ", replacement = "B", x = c ("abcb", "boy", "baby ")) [1] "aBcB" "Boy" "BaBy" # Replace only the first bsub (pattern = "B", replacement = "B", x = "baby ") [1] "Baby" sub (pattern = "B", replacement = "B", x = c ("abcb", "baby ")) [1] "aBcb" "Baby"

Grep and grepl

String Matching
The grep function returns the index value.
The grepl function returns the logical value.

# Returns the index grep (pattern = "boy", x = c ("abcb", "boy", "baby") of the matched element ")) [1] 2 # Return the logical value grepl (pattern = "boy", x = c ("abcb", "boy", "baby") [1] FALSE TRUE FALSE

Match & pmatch & charmatch

1. match
Usage
Match (x, table, nomatch = NA_integer _, incomparables = NULL)
X % in % table

Parameters:
X: vector or NULL: the values to be matched. Long vectors are supported.

Table: vector or NULL: the values to be matched against. Long vectors are not supported. (matched value)

Nomatch: the value to be returned in the case when no match is found. Note that it is coerced to integer. (no value returned on match)

Incomparables: a vector of values that cannot be matched. any value in x matching a value in this vector is assigned the nomatch value. for historical reasons, FALSE is equivalent to NULL. (different matching values)

The match function is similar to % in %. The difference is that match returns an index, while % in % returns a logical value.