Remove Hashes in R Output from R Markdown and Knitr - r-markdown

Question

I am using RStudio to write my R Markdown files. How can I remove the hashes (##) in the final HTML output file that are displayed before the code output?
As an example:
---
output: html_document
---
```{r}
head(cars)
```

Answer 1

You can include in your chunk options something like
comment=NA # to remove all hashes
or
comment='%' # to use a different character
More help on knitr available from here: http://yihui.name/knitr/options
If you are using R Markdown as you mentioned, your chunk could look like this:
```{r comment=NA}
summary(cars)
```
If you want to change this globally, you can include a chunk in your document:
```{r include=FALSE}
knitr::opts_chunk$set(comment = NA)
```

Answer 2

Just HTML
If your output is just HTML, you can make good use of the PRE or CODE HTML tag.
Example
```{r my_pre_example,echo=FALSE,include=TRUE,results='asis'}
knitr::opts_chunk$set(comment = NA)
cat('<pre>')
print(t.test(mtcars$mpg,mtcars$wt))
cat('</pre>')
```
HTML Result:
Welch Two Sample t-test
data: mtcars$mpg and mtcars$wt
t = 15.633, df = 32.633, p-value < 0.00000000000000022
alternative hypothesis: true difference in means is not equal to 0
95 percent confidence interval:
14.67644 19.07031
sample estimates:
mean of x mean of y
20.09062 3.21725
Just PDF
If your output is PDF, then you may need some replace function. Here what I am using:
```r
tidyPrint <- function(data) {
content <- paste0(data,collapse = "\n\n")
content <- str_replace_all(content,"\\t"," ")
content <- str_replace_all(content,"\\ ","\\\\ ")
content <- str_replace_all(content,"\\$","\\\\$")
content <- str_replace_all(content,"\\*","\\\\*")
content <- str_replace_all(content,":",": ")
return(content)
}
```
Example
The code also needs to be a little different:
```{r my_pre_example,echo=FALSE,include=TRUE,results='asis'}
knitr::opts_chunk$set(comment = NA)
resultTTest <- capture.output(t.test(mtcars$mpg,mtcars$wt))
cat(tidyPrint(resultTTest))
```
PDF Result
PDF and HTML
If you really need the page work in both cases PDF and HTML, the tidyPrint should be a little different in the last step.
```r
tidyPrint <- function(data) {
content <- paste0(data,collapse = "\n\n")
content <- str_replace_all(content,"\\t"," ")
content <- str_replace_all(content,"\\ ","\\\\ ")
content <- str_replace_all(content,"\\$","\\\\$")
content <- str_replace_all(content,"\\*","\\\\*")
content <- str_replace_all(content,":",": ")
return(paste("<code>",content,"</code>\n"))
}
```
Result
The PDF result is the same, and the HTML result is close to the previous, but with some extra border.
It is not perfect but maybe is good enough.