Thanks a lot.

You were right :-)

Professor Ripley can I use your SPLUS book for R too ?

2008/3/12, Prof Brian Ripley <ripley@stats.ox.ac.uk>:
>
> On Wed, 12 Mar 2008, Dwayne Blind wrote:
>
>
> > Dear R users,
> >
> > I wrote the following toy example to explain my problem :
> >
> > a=0
> > f=function(x,y,z) {
> >    if (a==0) x[1]+x[2]+y
> >    if (a!=0) x[1]+x[2]+y+z
> > }
> > f(1:2,3)
> >
> >
> > I have not specified z and I get an error.
>
>
> What was the error?  It works for me (so I've no idea), and returns NULL,
> the value of the last expression (invisibly).  I think you intended
>
> f <- function(x, y, z) if (a==0) x[1]+x[2]+y else x[1]+x[2]+y+z
>
> or
>
> f <- function(x, y, z) ifelse(a==0, x[1]+x[2]+y, x[1]+x[2]+y+z)
>
>
>
> > Although a=0, R seems to want to
> > know z because it's in the expression x[1]+x[2]+y+z.
> >
> > So I tried to put a default value :
> >
> > a=0
> > f=function(x,y,z=0) {
> >    if (a==0) x[1]+x[2]+y
> >    if (a!=0) x[1]+x[2]+y+z
> > }
> > f(1:2,3)
> >
> > Why isn't it working ? Sometimes everything is fine even though a
> parameter
> > is not specified.
> >
> > Thanks a lot.
> >
>
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@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.
> >
>
>
> --
> Brian D. Ripley,                  ripley@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
>

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