r - How to show code but hide output in RMarkdown?

Question

I want my html file to show the code, but not the output of this chunk:

```{r echo=True, include=FALSE}
fun <- function(b)
    {
    for(a in b)
        {print(a)
        return(a * a)}
    }
y <- fun(b)
```

When I run the code, i need the print to see the progress (it is quite a long function in reality).

But in the knitr file, I use the output in a further chunk, so I do not want to see it in this one (and there's no notion of progress, since the code has already been run).

This echo=True, include=FALSE here does not work: the whole thing is hidden (which is the normal behavior of include=FALSE).

What are the parameters I could use to hide the prints, but show my code?

Answer 1

As @ J_F answered in the comments, using {r echo = T, results = 'hide'}.

I wanted to expand on their answer - there are great resources you can access to determine all possible options for your chunk and output display - I keep a printed copy at my desk!

You can find them either on the RStudio Website under Cheatsheets (look for the R Markdown cheatsheet and R Markdown Reference Guide) or, in RStudio, navigate to the "Help" tab, choose "Cheatsheets", and look for the same documents there.

Finally to set default chunk options, you can run (in your first chunk) something like the following code if you want most chunks to have the same behavior:

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = T,
                      results = "hide")
```

Later, you can modify the behavior of individual chunks like this, which will replace the default value for just the results option.

```{r analysis, results="markup"}
# code here
```