[R] determining the order in which points are plotted

[David Winsemius]

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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David Winsemius, MD
Heritage Laboratories
West Hartford, CT