How to comment out multiple lines in R source code?

At 07:33 11/10/01 +0100, Prof Brian D Ripley <ripley at stats.ox.ac.uk> wrote:

On Wed, 10 Oct 2001, [iso-8859-1] G?ran Brostr?m wrote:

On 10 Oct 2001 rossini at blindglobe.net wrote:

"jl" == jonathan li <jonathan_li at agilent.com> writes:

    jl> Hi, Is there a way to comment out multiple lines at once in R
    jl> source code like C language's /* */ struct? This is quite
    jl> useful when one is testing different sections of a source
    jl> code.

One alternative is to use editor macros for this.

(X)Emacs, when using ESS, supports comment-region and uncomment-region
commands.

best,
-tony

You may also try

if (FALSE){
...
...
}

Yes, you will see that in e.g. the MASS scripts to comment out S code that
does not (yet) work in R.

One warning: in that method the `commented' code has to syntactically
valid, and that has caught me more than once.   So I usually use ESS's
methods.

In (X)Emacs, you can add a character at the beginning of several lines at
once by selecting a block of lines, and then typing C-x r t # (where you
can replace # by any other character or even a string; `C-x' means
`Ctrl-x'). This does not need ESS. You can even add the # in the middle of
the lines if your block selection starts at this point (in case you want to
comment out the right hand-side of a command... maybe not very usual).

BTW, the possibility to (un)comment out a block a R commands does not
appear in the ESS menu (it does in C-mode), and I did not find it in ESS's
doc (but I admit I did not read it all carefully).