Can I use knitr to apply CSS styles to individual table cells?

Question

Is it possible to apply a class attribute to individual table cells using knitr? I have successfully applied a class attribute to the section heading that contains a knitr::kable generated table and used that to format the entire table. However, I would like to be able to conditionally format individual cells which would require being able to apply a class to specific <td> elements.

My current workaround is to programmatically wrap the cell contents in a pair of <span> tags and pass that on to knitr::kable. This approach only allows me to format the text inside the cell versus the entire cell (e.g. setting the cell background color). Here's an example of what I'm currently using:

## Read in the report, process the data, send to kable
rpt <- generate.report()
mutate(rpt, Col2 = ifelse(abs(Col2) > Threshold,
                          paste('<span class="warning">',
                                sprintf("%.2f", Col2), '</span>'),
                          sprintf("%.2f", Col2))) %>%
  knitr::kable(format="markdown", align = c("l", rep("r", 4)),
               col.names = gsub("\\.", "<br>", colnames(.)))

Which results in the following example HTML output:

<td align="right"><span class="warning"> -1.74 </span></td>

I would like to be able to have knitr::kable generate something like this:

<td align="right" class="warning"> -1.74 </td>

That way I could apply css styles to the <td> tag vice the <span> tag.

Answer 1

package ReporteRs may help. Have a look here FlexTable.

You can then get the corresponding HTML code with function as.html and reuse it within your knitr code.