I presumed the original poster wanted a blank symbol (which could also be 
any character plotted in the background color). The point was that pch = 
26 does produce blank since it is unassigned. However, using NA would be a 
better solution. 





Prof Brian Ripley <ripley@stats.ox.ac.uk>
05/06/2003 08:04 AM

 
        To:     partha_bagchi@hgsi.com
        cc:     r-help@stat.math.ethz.ch, <tblackw@umich.edu>
        Subject:        Re: [R] null plotting symbol ?


On Tue, 6 May 2003 partha_bagchi@hgsi.com wrote:

> pch = 26 seems to produce a blank symbol.

More accurately, it plots nothing.  (A `blank' symbol' suggests to me that
it plots in the background colour.)  That is true *currently* (26-31 are
unassigned), but there is no guarantee that will remain so.

Why would one use that rather than NA, whose meaning is clear?

In brief: what exactly was your point?  Were you seriously suggesting
using pch=26?

> Prof Brian Ripley <ripley@stats.ox.ac.uk>
> Sent by: r-help-bounces@stat.math.ethz.ch
> 05/05/2003 04:39 PM
>
>
>         To:     tblackw@umich.edu
>         cc:     r-help@stat.math.ethz.ch
>         Subject:        Re: [R] null plotting symbol ?
>
>
> NAs in pch cause the corresponding points to be omitted.
>
> On Mon, 5 May 2003 tblackw@umich.edu wrote:
>
> > I am calling  plot()  with argument pch as a vector of numeric
> > symbol codes, the same length as x and y.  Is there some code
> > which produces no symbol - a blank - so that I can come back
> > with a second call to  points()  and fill in these locations
> > using a different fill color and a different symbol size ?

--
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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