[R] legends in ggplot

[David Barron]

Is it possible to change the legend title in ggplot that is generated
by a colour (other than by changing the name of the variable)?  For
example, this produces a legend title, "tip/total_bill".  How can that
title be changed?

ggpoint(ggplot(tips,aesthetics=list(y=tip,x=total_bill,colour=tip/total_bill)) )

Thanks.

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David Barron
Said Business School
University of Oxford
Park End Street
Oxford OX1 1HP