convert HTML Character Entity Encoding in R

Question

Is there a way in R to convert HTML Character Entity Encodings?

I would like to convert HTML character entities like & to & o

Answer 1

While the solution by Jeroen does the job, it has the disadvantage that it is not vectorised and therefore slow if applied to a large number of characters. In addition, it only works with a character vector of length one and one has to use sapply for a longer character vector.

To demonstrate this, I first create a large character vector:

set.seed(123)
strings <- c("abcd", "& ' >", "&", "€ <")
many_strings <- sample(strings, 10000, replace = TRUE)

And apply the function:

unescape_html <- function(str) {
  xml2::xml_text(xml2::read_html(paste0("", str, "")))
}

system.time(res <- sapply(many_strings, unescape_html, USE.NAMES = FALSE))
##    user  system elapsed 
##   2.327   0.000   2.326 
head(res)
## [1] "& ' >" "€ <"   "& ' >" "€ <"   "€ <"   "abcd" 

It is much faster if all the strings in the character vector are combined into a single, large string, such that read_html() and xml_text() need only be used once. The strings can then easily be separated again using strsplit():

unescape_html2 <- function(str){
  html <- paste0("", paste0(str, collapse = "#_|"), "")
  parsed <- xml2::xml_text(xml2::read_html(html))
  strsplit(parsed, "#_|", fixed = TRUE)[[1]]
}

system.time(res2 <- unescape_html2(many_strings))
##    user  system elapsed 
##   0.011   0.000   0.010 
identical(res, res2)
## [1] TRUE

Of course, you need to be careful that the string that you use to combine the various strings in str ("#_|" in my example) does not appear anywhere in str. Otherwise, you will introduce an error, when the large string is split again in the end.