R help - Aug 2008 - Documenting a function: How to get the comments in a function similar to args()

Hi All,

Imagine that we have a function defined as follows:
foo <- 
# comments line 1
# comments line 2
# etc..
function(x){
x <- 2
}
I can use args(foo) to get the arguments for foo. Is there any function to
get 
the comment lines at the beginning of the function?
>From what I understand the prompt() function allows one to create a .Rd file
which
can be compiled but I am not there yet. 
On page 31 of "Programming with Data" (J. Chambers) one can read that
the
help ? function does what I want but It does not work the same way in R I
guess.
I use R version 2.7.0 on Win XP.
Thank you for your time.
AA.

What are the comments line at the beginning of the function?  if you
just type in the function name then you get the code, and it seems
that R removes the comment lines to make the code more readable.  I
just looked at a function in a package that I created and know that
there are comments in there.  If you need the comments I would look in
the source package.  I believe that if you go to the folder where
packages are installed then you can get to the sorces.  I think this
is what you want.

On Thu, Aug 14, 2008 at 7:15 PM, A.Ajakh <aajakh at stonebrook.ws>
wrote:
> Hi All,
>
> Imagine that we have a function defined as follows:
> foo <-
> # comments line 1
> # comments line 2
> # etc..
> function(x){
> x <- 2
> }
> I can use args(foo) to get the arguments for foo. Is there any function to
> get
> the comment lines at the beginning of the function?
> >From what I understand the prompt() function allows one to create a .Rd
file
> which
> can be compiled but I am not there yet.
> On page 31 of "Programming with Data" (J. Chambers) one can read
that the
> help ? function does what I want but It does not work the same way in R I
> guess.
> I use R version 2.7.0 on Win XP.
> Thank you for your time.
> AA.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods. We are mammals, and have not exhausted the
annoying little problems of being mammals.

	-K. Mullis

Try this (provided the comments are actually _in_ the function -- in
the example you gave they are not).
> foo <-
+ function(x){
+ # comments line 1
+ # comments line 2
+ # etc..
+ x <- 2
+ }
>
> grep("^#", attr(foo, "source"), value = TRUE)
[1] "# comments line 1" "# comments line 2" "#
etc.."

Also be aware of the keep.source option:  ?options

On Thu, Aug 14, 2008 at 7:15 PM, A.Ajakh <aajakh at stonebrook.ws>
wrote:
> Hi All,
>
> Imagine that we have a function defined as follows:
> foo <-
> # comments line 1
> # comments line 2
> # etc..
> function(x){
> x <- 2
> }
> I can use args(foo) to get the arguments for foo. Is there any function to
> get
> the comment lines at the beginning of the function?
> >From what I understand the prompt() function allows one to create a .Rd
file
> which
> can be compiled but I am not there yet.
> On page 31 of "Programming with Data" (J. Chambers) one can read
that the
> help ? function does what I want but It does not work the same way in R I
> guess.
> I use R version 2.7.0 on Win XP.
> Thank you for your time.
> AA.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Along the lines of Gabor's method, presumably you could put a
"spare"
argument in your function:


foo<- function(x,help=FALSE,...)
{
helpout<-c(comment,
comment,
end of comments)
if(something_is_wrong_with_inputs || help=TRUE)
	{
	print(helpout)
	stop #or trycatch, or whatever you prefer
	}
[remainder of function]
}

I know that's sloppy but I'm new to R.

Carl

Thanks to everyone who responded. It was all very helpful.
AA.


A.Ajakh wrote:
> 
> Hi All,
> 
> Imagine that we have a function defined as follows:
> foo <- 
> # comments line 1
> # comments line 2
> # etc..
> function(x){
> x <- 2
> }
> I can use args(foo) to get the arguments for foo. Is there any function to
> get 
> the comment lines at the beginning of the function?
>>From what I understand the prompt() function allows one to create a .Rd
file
> which
> can be compiled but I am not there yet. 
> On page 31 of "Programming with Data" (J. Chambers) one can read
that the
> help ? function does what I want but It does not work the same way in R I
> guess.
> I use R version 2.7.0 on Win XP.
> Thank you for your time.
> AA.
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
> 
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