R remove non-alphanumeric symbols from a string

Another approach to handle this question

library(stringr)
text =  c("This is a string.  In addition, this is a string!")
str_split(str_squish((str_replace_all(text, regex("\\W+"), " "))), " ")
#[1] "This"     "is"       "a"        "string"   "In"       "addition" "this"     "is"       "a"        "string"  

• str_replace_all(text, regex("\\W+"), " "): find non-word character and replace " "
• str_squish(): reduces repeated whitespace inside a string
• str_split(): split up a string into pieces

here is an example:

> str <- "This is a string. In addition, this is a string!"
> str
[1] "This is a string. In addition, this is a string!"
> strsplit(gsub("[^[:alnum:] ]", "", str), " +")[[1]]
 [1] "This"     "is"       "a"        "string"   "In"       "addition" "this"     "is"       "a"       
[10] "string"