Use Regex to highlight a text in HTML generated with Rmarkdown - r-markdown

Question

I have a vector with a tokenized text and some other vectors of regular expressions, like this:
text <- c("When", " ", "Claire", " ", "visited", " ", "the", " ", "Statue", " ", "of", " ", "Liberty", " ", "for", " ", "the", " ", "first", " ", "time", ",", " ", "she", " ", "instantly", " ", "admired", " ", "it", " ", "as", " ", "a", " ", "symbol", " ", "of", " ", "freedom", ".")
green <- c("^I$", "^you$", "^he$", "^she$", "^it$", "^we$", "^they$")
blue <- c("^the$", "^a$", "^an$")
yellow <- c("ed$")
How can I knit an HTML using Rmarkdown with the text printed as a human-readable text with the regular expressions highlighted with different colors ? Like this:
Thank you.

Answer 1

One option to achieve your desired result may look like so:
---
output: html_document
---
```{r echo=FALSE}
text <- c("When", " ", "Claire", " ", "visited", " ", "the", " ", "Statue", " ", "of", " ", "Liberty", " ", "for", " ", "the", " ", "first", " ", "time", ",", " ", "she", " ", "instantly", " ", "admired", " ", "it", " ", "as", " ", "a", " ", "symbol", " ", "of", " ", "freedom", ".")
green <- c("^I$", "^you$", "^he$", "^she$", "^it$", "^we$", "^they$")
blue <- c("^the$", "^a$", "^an$")
yellow <- c("ed$")
```
```{r}
regex <- lapply(list(lightgreen = green, cyan = blue, yellow = yellow), function(x) {
x <- paste(x, collapse = "|")
paste0("(", x, ")")
})
for (i in seq_along(regex)) {
text <- gsub(regex[[i]], paste0("<span style='background-color:", names(regex)[i], "'>\\1</span>"), text)
}
```
`r paste(text, collapse = "")`