R help - May 2007 - optional fields in function declarations; Solved

thank you to both Adaikalavan and Patrick.


on the basis of Adaikalavan example this is an example that point out  my
problems.
>log_raise=function(num, exp, base){return(log(num^exp,base))}
I would like to have optional fields, so some settings to be default parameters;
if I declare the function as above the operator must of course input all the
variables.

Finally I could fix as follow.
> log_raise=function(num, exp=2, base=exp){return(log(num^exp,base))}
thank you helps, cheers



Claudio


Patrick Burns

---------- Initial Header -----------
>From      : "Adaikalavan Ramasamy" ramasamy at cancer.org.uk
To          : "claudio.is at libero.it" claudio.is at libero.it
Cc          : "r-help" r-help at stat.math.ethz.ch
Date      : Sun, 20 May 2007 00:21:32 +0100
Subject : Re: [R] optional fields in function declarations






> Can you provide an simple example of what you want the function to do?
> 
> Generally, I set some value in the default.
> 
> raise <- function(x, power=1){ return( x^power ) }
> 
>  > raise(5)
> [1] 5
>  > raise(5,3)
> [1] 125
> 
> 
> Or you can do the same but in a slightly unclear manner.
> 
> raise <- function(x, power){
>    if(missing(power)) power <- 1
>    return( x^power )
> }
> 
> I prefer the former.
> 
> Regards, Adai
> 
> 
> 
> claudio.is at libero.it wrote:
> > Dear R users,
> > 
> > I need to create a set of function to solve some tasks. I want to
leave the operator to decide whether uses default parameters or change it; so
the functions may have some optional fields. I tied to use the function
missing(), but it will work properly only if the optional field is decleared at
last in the function.
> > Can you give me some suggestion an some reference?
> > 
> > thank you.
> > 
> > 
> > Claudio
> > 
> > 
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> > 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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