78

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)
```

enter image description here

Michael Harper
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mchangun
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    It's worth considering the purpose of the hashes. They make it easy for R code to be copied and pasted from your document into R console, because the R output is commented out by the hashes and so will be ignored. – Gregory Mar 09 '13 at 16:50
  • You can also `command + shift + c` on a mac or `control + shift + c` on a pc to remove the hashtags if you need – rawr Feb 02 '14 at 18:26

2 Answers2

129

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$set(comment = NA)
```
Michael Harper
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Gary Weissman
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    If you want to remove hashes from all output, you can set `opts_chunk$set(comment = NA)`. – Ramnath Feb 27 '13 at 18:56
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    And if you want the result to show up as if it wasn't code at all but rather regular text, you can use `results='asis'`, and `comment` isn't necessary. – Molx Jun 02 '15 at 19:39
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    @Ramnath you should probably mention that in order for this to work you need to add `library(knitr)` to the cell. – cbrnr Mar 27 '17 at 08:09
4

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 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.

HTML Result in the mixed version

It is not perfect but maybe is good enough.

Thiago Mata
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