library(stringr)

1. Statistical character segment length:

str_length(c("ab", "R for data science", NA))
#>[1] 2 18 NA

2. String combination

To combine two or more strings, you can use the str_c() function:

str_c("x", "y", "z")
#>[1] "xyz"

You can use the sep parameter to control the separation between strings:

str_c("x", "y", sep = ", ")
#>[1] "x, y"

The str_c() function is vectorized, it can automatically loop the short vector so that it has the same length as the longest vector:

str_c("prefix-", c("a", "b", "c"), "-suffix")
#> [1] "prefix-a-suffix" "prefix-b-suffix" "prefix-c-suffix"

To merge character vectors into strings, you can use the collapse() function:

str_c(c("x", "y", "z"), collapse = ", ")
#> [1] "x, y, z"

3. Subset of strings

You can use the str_sub() function to extract part of the string. In addition to string parameters, there are start and end parameters in the str_sub() function, which give the position of the substring (including start and end):

x <- c("Apple", "Banana", "Pear")
str_sub(x, 1, 3)
#> [1] "App" "Ban" "Pea"

Negative number means counting from back to front

str_sub(x, -3, -1)
#> [1] "ple" "ana" "ear"

4. Case conversion

str_to_upper(c("a", "b"))
#>[1] "A" "B"
str_sub(x, 1, 1) <- str_to_lower(str_sub(x, 1, 1)) x
#> [1] "apple" "banana" "pear"