Character string functions
casefold() function
chartr() function
grep functions
agrep() and agrepl() functions
charToRaw() function
gregexpr() function
grep() and grepl() functions
grepRaw() function
regexpr() function
sub() and gsub() functions
substr() and substring() functions
tolower() and toupper() functions
Classes
array
attributes
data frames
difftime() function
dimnames() function
factor levels (factor/ordered)
formulas
glm()/lm() functions ...