在markdown中抑制消息，但不在R控制台中

Question

I currently use the following header:

```{r, message=FALSE} 
foo <- function(x) message(x)
for(i in 1:10) foo(i)
```

Inside this code chunk, there is a loop over simulated scenarios, with message() function that prints status of currently executed scenario.

I would like to suppress those messages from display in RStudio and final HTML output, but I still want to control the simulation progress and see the message() output in console. Is this achievable? Maybe with other arguments/functions?

Answer 1

You can write/append status to a file (this is a workaround solution, there should be a more direct answer).

For example:

file <- file("status.txt", open = "wt")
sink(file, type = "message")
message("all good")

In this example message won't be displayed - it'll be written to a status.txt file.

In you're using specific function and iterating over a set you can try this example:

foo <- function(x) {
    message(x)
}

file <- file("status.txt", open = "wt")
sink(file, type = "message")
for(i in 1:3) {
    foo(i)
}

Function foo should return (message) value, however it appends it to a status.txt file.

You can track changes in status.txt file using bash tail command with -f argument. First send R to background and then use tail -f status.txt in your console.

Answer 2

One approach would be to put this in the start of your file.

mymessage <- function (text) {   
  if(knitr::opts_knit$get('out.format') != NULL) message(text) 
}

There are various ways to know if you are within knitr, recent versions have knitr::is_latex_output and similar.