Hide printing statement in RMarkdown

Question

Is there a way to hide printing statements in RMarkdown? I have written a function, which prints progress about the learning behavior of an algorithm to the R console. Here is an example:

f <- function() {
  print("Some printing")
  return(1)
}

In RMarkdown I have

```{r, eval = TRUE, results = "show"}
res = f()
print(res)
```

This adds "Some printing" and 1 into the RMarkdown output file. Is there a way to suppress "Some printing", but keep the output of the function (here 1)? For warnings, errors and messages there are options, but I could find none for print statements.

Answer 1

If you use message in your function instead of print, you can suppress the message

```{r} 
f <- function() {
    message("Some printing")   # change this line
    return(1) 
}

res <- f()    
print(res)    # original prints both  
```
#> Some printing
#> [1] 1

either explicitly with suppressMessages:

```{r} 
res <- suppressMessages(f())
print(res) 
```
#> [1] 1

or via the message=FALSE chunk option:

```{r, message=FALSE} 
res <- f()
print(res) 
```
#> [1] 1

Messages designed for this kind of use. If you really want to keep print, you could subset (which is awkward), or use capture.output to capture and store the message while storing the result in another variable:

```{r}
f <- function() {
    print("Some printing")
    return(1)
}

trash <- capture.output(res <- f())   
print(res)
```
#> [1] 1

...but that's still pretty awkward.