Is it possible to view an HTML table in the viewer pane?

Question 1

Here is a quick way to do this in RStudio

view_kable <- function(x, ...){
  tab <- paste(capture.output(kable(x, ...)), collapse = '\n')
  tf <- tempfile(fileext = ".html")
  writeLines(tab, tf)
  rstudio::viewer(tf)
}
view_kable(head(df[,1:9]), format = 'html', table.attr = "class=nofluid")

If the kable function can return an object of class kable, then one could rename view_kable as print.kable in which case merely calling the kable function would open the table in the viewer. If you think this is useful, please go ahead and file a feature request on the knitr github page.

Question 2

I have a solution that works for kable tables.

kable(iris) %>% kableExtra::kable_styling()

This is automatically displayed in the viewer pane. No need for tempfile.

Question 3

I have this functionality in my htmlTable package and the function is rather simple:

print.htmlTable<- function(x, useViewer = TRUE, ...){
  # Don't use viewer if in knitr
  if (useViewer &&
        !"package:knitr" %in% search()){

    htmlFile <- tempfile(fileext=".html")
    htmlPage <- paste("<html>",
                      "<head>",
                      "<meta http-equiv=\"Content-type\" content=\"text/html;charset=UTF-8\">",
                      "</head>",
                      "<body>",
                      "<div style=\"margin: 0 auto; display: table; margin-top: 1em;\">",
                      x,
                      "</div>",
                      "</body>",
                      "</html>", sep="\n")
    cat(htmlPage, file=htmlFile)

    viewer <- getOption("viewer")
    if (!is.null(viewer) &&
          is.function(viewer)){
      # (code to write some content to the file)
      viewer(htmlFile)
    }else{
      utils::browseURL(htmlFile)
    }
  }else{
    cat(x)
  }
}

RStudio recommends that you use the getOption("viewer") instead of @Ramnath's suggestion, the raw RStudio::viewer(). My solution also adds the utils::browserURL() in case you are not using RStudio. I got the idea from this blog post.

Question 4

As was explained on this RStudio Support page, the key is to use tempfile() :

Note that the Viewer pane can only be used for local web content. This content can either be static HTML files written to the session temporary directory (i.e. files with paths generated by the tempfile function) or a locally run web application.

See my answer to this question for a bare-bones example.

Question 5

For kable objects, we can use print.kableExtra

library(knitr)

x <- kable(head(iris), format = "html")

library(kableExtra)

class(x) <- c("kableExtra", class(x))
print(x)