how do you color the cell in rmarkdown pdf output

Question

I cannot get cellcolor to work in rmarkdown:

---
header-includes:
   -  \usepackage{colortbl} 
   -  \usepackage{color} 

output:
    pdf_document
---

```{r, results="asis"}

library(xtable)
# Your data
tab = data.frame(category = c("A","B","C"), groupA = c(.2,.3,.5), groupB= c(.6,.7,.9))

# Function to cut your data, and assign colour to each range
f <- function(x) cut(x, c(0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, Inf), 
                      labels=c("green", "red", "blue", "orange", "yellow", "purple", "brown", "white"),
                      include.lowest = FALSE, right = TRUE)

# Apply function to columns: this overwrites your data
tab[c("groupA", "groupB")] <- lapply(tab[c("groupA", "groupB")], function(x)
                                            paste0("\\cellcolor{", f(x), "}", x))
# Sanitise output 
print(xtable(tab), sanitize.text.function = identity)
```

I keep getting this error:

! Undefined control sequence.
l.155 1 & A & \cellcolor

Any ideas what does cellcolor needs to work?

Answer 1

Update

The OP's example works for me when including \usepackage[dvipsnames]{xcolor} instead. For another approach see below.

Alternative Approach

Here is another approach using the very handy condformat package. This way you don't have to include any TeX packages by hand and don't have to worry about escaping special characters etc.

---

We basically create a condformat_tbl object and add two formatting rules for each column.

---
output:
    pdf_document
---

```{r, include = F}
library(condformat)
cols        <- c('green', 'red', 'blue', 'orange', 
                 'yellow', 'purple', 'brown', 'white')
names(cols) <- cols # important for the colours arg in rule_fill_discrete
                    # since it matches the result of 'expression' with the names of the 'colours' vector

f   <- function(x) cut(x, c(0, seq(.2, .8, .1), Inf), labels = cols,
                       include.lowest = FALSE, right = TRUE)
tab <- data.frame(category = c('A', 'B', 'C'), 
                  groupA = c(.2, .3, .5), 
                  groupB = c(.6, .7, .9))
```


```{r, results = 'asis', echo = F}
condformat(tab) + 
  rule_fill_discrete(groupA, expression = f(groupA), colours = cols) +
  rule_fill_discrete(groupB, expression = f(groupB), colours = cols) 
```

Notice, that the value for the colours argument in rule_fill_discrete is vector of key-value pairs. The keys are the possible results of the expression.

And this is what you get: