specifying output path for knit2html

Question

I'm having trouble specifying an output path for the html generated by knit2html or its dependent functions. I would like to specify 'outfile' in the the call to knit2html(), but I get the error,

Error in knit2html(input = "test.Rmd", output = "test-abcd.html") :
object 'outfile' not found

'output' is a parameter of markdownToHTML which should work I'd think. I can't find anywhere in the source where 'outfile' is used.

This should reproduce my experience.

library(knitr)
library(markdown)

# a minimal example
writeLines(c("```{r hello-random, echo=TRUE}", "rnorm(5)", "```"), 
           "test.Rmd")

# this works and outputs to test.html
knit2html(input = "test.Rmd")

# this generates the above error
knit2html(input   = "test.Rmd", 
          output  = "test-abcd.html")

# breaking it down into two steps works in this simple case,
# but not in my application.  trying to diagnose that difference currently
knit("test.Rmd")    
markdownToHTML("test.md", 
               output="test-abcd.html")

relevant version info might be useful?

sessionInfo()
R version 3.0.0 (2013-04-03)
Platform: x86_64-pc-linux-gnu (64-bit)

other attached packages:
[1] plyr_1.8         knitr_1.2        digest_0.6.3     markdown_0.5.4   xtable_1.7-1     reshape2_1.2.2   scales_0.2.3     ggplot2_0.9.3.1  data.table_1.8.8

Answer 1

First, thanks for the very clear and reproducible question. If you take a look at the knit2html function source code, you can understand what the problem is :

R> knit2html
function (input, ..., envir = parent.frame(), text = NULL, quiet = FALSE, 
    encoding = getOption("encoding")) 
{
    if (is.null(text)) {
        out = knit(input, envir = envir, encoding = encoding, 
            quiet = quiet)
        markdown::markdownToHTML(out, outfile <- sub_ext(out, 
            "html"), ...)
        invisible(outfile)
    }
    else {
        out = knit(text = text, envir = envir, encoding = encoding, 
            quiet = quiet)
        markdown::markdownToHTML(text = out, ...)
    }
}
<environment: namespace:knitr>

If the text argument is NULL (ie, if you provide a file as input instead of a character vector), then the given file is passed to the knit function, and the markdownToHTML function is called the following way :

markdown::markdownToHTML(out, outfile <- sub_ext(out, "html"), ...)

So in this case the output file name is generated by substituting the existing file name extension with html, and you can't provide your own output filename as an argument.