[R] Adding a legend to a (multi-facet) plot produced by ggplot().

[Rolf Turner]

I have been struggling to add a legend as indicated in the subject line,
with no success at all.  I find the help to be completely bewildering.

I have attached the code of what I have tried in the context of a simple
reproducible example.

I have also attached a pdf file of a plot produced with base graphics to 
illustrate roughly what I am after.

I would be grateful if someone could point me in the right direction.

cheers,

Rolf Turner

-- 
Honorary Research Fellow
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276

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