Character classes :

  Set of characters enclose din a square bracket [ ].

  Matches only the character enclose din the bracket Can be sued in conjunction with the quantifiers.

  A caret (^) ahead of the expression negates the expression

[aeiou]	Matches lower case vowels
[AEIOU]	Matches upper case vowels
[0123456789]	Matches any digits
[0-9]	Matches any digits
[a-z]	Matches any lower case letter
[A-Z]	Matches any upper case letters
[a-zA-Z0-9]	Matches any of above classes
[^aeiou]	Matches everything except aeiou
[^0-9]	Matches everything except digits

POSIX Character classes :

  Enclosed within double brackets [[ ]]

  Works same like character classes

  A caret (^) ahead of the expression negates the expression

[[:lower:]]	Matches lower case letter
[[:upper:]]	Matches upper case letter
[[:alpha:]]	Matches letter
[[:digit:]]	Matches digits
[[:space:]]	Matches space characters(\t,\n,space etc)
[[:blank:]]	Matches blank characters
[[:alnum:]]	Matches Alphanumeric characters
[[:cntrl:]]	Matches control characters
[[:punct:]]	Matches punctuation characters
[[:xdigit:]]	Matches hexadecimal digits
[[:print:]]	Matches printable characters [[:alpha:]] [[:punct:]] and space
[[:graph:]]	Matches Graphical characters comprise [[:alpha:]] and [[:punct:]]

Matches Graphical characters comprise [[:alpha:]] and [[:punct:]]

library(readtext)
library(stringr)
data #To split the string using a pattern
data=unlist(str_split(data$text,” “))
#To matche character classes
#To match digit
grep(pattern = “[0-9]”,data,value=T )
#To match any upper case letter
grep(pattern = “[A-Z]”,x = data,value = T)
#To match POSIX Character classes
#To match digit
grep(pattern =”[[:digit:]]”,data,value=T)
#To match any upper case letter
grep(pattern = “[[:upper:]]”,x = data,value = T)
#To match punctuation character
grep(pattern = “[[:punct:]]”,x = data,value = T)