R help - Apr 2003 - How to count the number of parameters in a function

I have the following function:
Myfunc <- function(var1,var2,.....,varN)
{ .....
}
In the above function I have a variable number of parameters (N>2). How can
I count how many parameters have been entered?

Any help appreciated

Thanks

Arno

On Wed, 9 Apr 2003 arnaud_amsellem at ssga.com wrote:
> I have the following function:
> Myfunc <- function(var1,var2,.....,varN)
> { .....
> }
> In the above function I have a variable number of parameters (N>2). How
can
> I count how many parameters have been entered?
Well, that example will not parse. If you had

Myfunc <- function(...)
{
    dots <- list(...)
    cat("#args is", length(dots), "\n")
}

you would be able to see how it might be done.

Another way is to use match.call(expand.dots=TRUE), as in

Myfunc <- function(...)
{
    Call <- match.call(expand.dots=TRUE)
    cat("#args is", length(Call) - 1, "\n")
}

the first element being the function name.  In this version you can have
named formal arguments and ... .


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

You can use list(...):

Myfunc<-function(...)
{
d<-list(...)
n<-length(d)
## Other instructions
return(n)
}

##  Example:

var1<-runif(20)
var2<-rnorm(20)
var3<-rpois(20, 2)
Myfunc(var1, var2, var3)

Hope this helps,

Clem.



At 08:55 09/04/2003 +0100, arnaud_amsellem at ssga.com
wrote:
>I have the following function:
>Myfunc <- function(var1,var2,.....,varN)
>{ .....
>}
>In the above function I have a variable number of parameters (N>2). How
can
>I count how many parameters have been entered?
>
>Any help appreciated
>
>Thanks
>
>Arno
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://www.stat.math.ethz.ch/mailman/listinfo/r-help

On Wed, 9 Apr 2003 arnaud_amsellem at ssga.com wrote:
> I have the following function:
> Myfunc <- function(var1,var2,.....,varN)
> { .....
> }
> In the above function I have a variable number of parameters (N>2). How
can
> I count how many parameters have been entered?
>
using `lm' as example:

length(formals(lm))

best,

Torsten
> Any help appreciated
>
> Thanks
>
> Arno
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>
>