char_tolower: Convert the case of character objects
In koheiw/quanteda.core: Quantitative Analysis of Textual Data

char_tolower and char_toupper are replacements for base::tolower() and base::tolower() based on the stringi package. The stringi functions for case conversion are superior to the base functions because they correctly handle case conversion for Unicode. In addition, the *_tolower() functions provide an option for preserving acronyms.

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char_tolower(x, keep_acronyms = FALSE)

char_toupper(x)

`x`	the input object whose character/tokens/feature elements will be case-converted
`keep_acronyms`	logical; if `TRUE`, do not lowercase any all-uppercase words (applies only to `*_tolower()` functions)

txt1 <- c(txt1 = "b A A", txt2 = "C C a b B")
char_tolower(txt1)
char_toupper(txt1)

# with acronym preservation
txt2 <- c(text1 = "England and France are members of NATO and UNESCO",
          text2 = "NASA sent a rocket into space.")
char_tolower(txt2)
char_tolower(txt2, keep_acronyms = TRUE)
char_toupper(txt2)