wrap text in knitr::kable table cell using "\n"

Question

How can I wrap a cell in a knitr::kable table cell using \n?

---

I want to generate a .rmd file containing some tables where one column needs text wrapping. The places where the wrapping should occur are marked with \n. I tried (this is a standalone .rmd document):

---
output: pdf_document
---

## A Table with text wrap

```{r cars}
knitr::kable(data.frame(col1 = c("a", "b"), col2 = c("one\ntwo", "three\nfour")))
```

..but this doesn't work. Instead of staying in col2, the wrapped part lives on the next line of col1.

Expected output is:

col1 | col2
-------------
a    | one
     | two
b    | three
     | four

Solutions using other packages than knitr are welcome as long as they allow to print (nearly) as nice.

Lejeune

Answer 1

A fire-and-forget solution for flexible dual HTML/PDF of standard tables. It incorporates kableExtra's linebreak function outlined by @snoram.
Assumption: You use <br> as your line break indicator.

```{r}
knit_table(df1)
```

Code

library(dplyr)
library(knitr)
library(kableExtra)

knit_table <- function(df){
  if (is_html_output()) {
    df %>%
      kable("html", escape = F) %>%
      kable_styling()
  } else {
    df <- data.frame(lapply(df, function(x) {gsub("<br>", "\n", x)}), stringsAsFactors = F)

    df %>%  
      mutate_all(linebreak) %>%
      kable("latex", booktabs = T, escape = F)  
  }
}

Data

df1 <- data.frame(col1 = c("a", "b"),
                  col2 = c("one<br>two", "three<br>four"))

Convert

Thanks @Convert for this extremely simple solution. It is exactly what I was searching for, since the \n's were a choice I can easily change to <br>. This however only works for html output, at least for me. Does it also work for pdf output for you? – Lejeune

You both are absolutely right. I adapted the approach for dual-use. – Convert

Answer 2

If you don't mind using kableExtra you can definitely achieve this, here is one example:

library(kableExtra)
knitr::kable(data.frame(col1 = c("a", "b"), col2 = linebreak(c("one\ntwo", "three\nfour"))),
             escape = FALSE)

More details here.

Eogene

Thanks. Unfortunately, this throws an error for me: Error in linebreak(c("one\ntwo", "three\nfour")) : could not find function "linebreak". What package does the linebreak function come from? – Lejeune

kableExtra, you first need to install and then add library(kableExtra) to your script... – Eogene

Thanks, @snoram. I unfortunately had an old version of kableExtra installed. Changed that. Now the code runs. For pdf output it works perfectly, for html output it produces an empty col2. Does it also work for html output for you? – Lejeune

I just checked and it doesn't work in html. So instead you could use Roman's solution or open a new question if it is important to have one solution that works for both. – Eogene