R help - Jan 2011 - determining the order in which points are plotted

I make plenty of scatterplots, especially using scatterplot.matrix from 
library(car).  One thing I don't know how to do is determine which points 
are plotted last.  Sometimes I plot a large number of points for multiple 
groups represented by different colors.

I would like to guarantee that point that are far from the centroid for 
their group are plotted last.  This way they will be visible because they 
won't be buried under a pile of points from another group.

As it stands, it looks like scatterplot.matrix (and maybe other plotting 
functions) lay down a group at a time, in order, so that the first group 
is most likely to be buried under later groups.  I try to sort factor 
levels so that the biggest groups go first, and that helps a little, but 
it isn't the complete solution I'm looking for.

Thanks in advance.

Mike

--
Michael B. Miller, Ph.D.
Minnesota Center for Twin and Family Research
Department of Psychology
University of Minnesota

On Jan 24, 2011, at 6:49 PM, Mike Miller wrote:
> I make plenty of scatterplots, especially using scatterplot.matrix  
> from library(car).  One thing I don't know how to do is determine  
> which points are plotted last.  Sometimes I plot a large number of  
> points for multiple groups represented by different colors.
?points
>
> I would like to guarantee that point that are far from the centroid  
> for their group are plotted last.  This way they will be visible  
> because they won't be buried under a pile of points from another  
> group.
>
> As it stands, it looks like scatterplot.matrix (and maybe other  
> plotting functions) lay down a group at a time, in order, so that  
> the first group is most likely to be buried under later groups.  I  
> try to sort factor levels so that the biggest groups go first, and  
> that helps a little, but it isn't the complete solution I'm looking
> for.
>
> Thanks in advance.
>
> Mike
>
> --
> Michael B. Miller, Ph.D.
> Minnesota Center for Twin and Family Research
> Department of Psychology
> University of Minnesota
>
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