Data Science Desktop Survival Guide by Graham Williams
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Sub-Strings in Base R

The base function base::substr() can be used to extract and replace parts of a string similar to stringr::str_sub(). Note however that it does not handle negative values and that string replacement only replaces the same length as the replacement string, without changing the length of the original string.

s <- "string manipulation"
substr(s, start=3, stop=6)

## [1] "ring"

substr(s, 3, 6)

## [1] "ring"

substr(s, 1, 12) <- "stip"
s

## [1] "stipng manipulation"

The base::substring() function performs similarly though uses last= rather than stop=.

s <- "string manipulation"
substring(s, first=3, last=6)

## [1] "ring"

x <- c("abcd", "aabcb", "babcc", "cabcd")
substring(x, 2, 4)

## [1] "bcd" "abc" "abc" "abc"

substring(x, 2, 4) <- "AB"
x

## [1] "aABd"  "aABcb" "bABcc" "cABcd"