[R] 'text' can't find "x"

[ripley@stats.ox.ac.uk]

On Thu, 17 Oct 2002, [iso-8859-1] Göran Broström wrote:

> I wanted to add some text to a plot and got (R-1.6.0, Linux):
>
> >  text(x = c(1, 4), y = 5, labels = x)
> Error in text.default(x = c(1766, 1895), y = 5, labels = x) :
>         Object "x" not found
>
> With the default value of 'labels':
>
> >  text(x = c(1, 2), y = 5, labels = seq(along = x))
> Error in seq(along = x) : Object "x" not found
>
> A scoping bug? :)

No, a scoping misunderstanding.  Default arguments are evaluated in the
frame of the function: explicit values in the frame of the caller.

See `S Programming' p.44, for example.

>
> But
>
> >  text(x = c(1, 2), y = 5)
>
> is OK. Doesn't give the labels I want, though. But why does it work, i.e.,
> why is 'x' found in this case and not when I write out the default?
>
> ---
>  Göran Broström                    tel: +46 90 786 5223
>  Department of Statistics          fax: +46 90 786 6614
>  Umeå University                   http://www.stat.umu.se/egna/gb/
>  SE-90187 Umeå, Sweden             e-mail: gb at stat.umu.se
>
>
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-- 
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)
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