bottom legends in ggplot2 ?

I would think that the lines below should work but they give an error.
Hadley, can you clarify this?

Cheers,

Thierry

library(ggplot2)
qplot(mpg, wt, data=mtcars, colour=cyl) + opts(legend.position =

"bottom")
Error in grid.Call.graphics("L_setviewport", pvp, TRUE) :
?Non-finite location and/or size for viewport

ggplot(mtcars, aes(x = mpg, y = wt, colour = cyl)) + geom_point() +

opts(legend.position= "bottom")
Error in grid.Call.graphics("L_setviewport", pvp, TRUE) :
?Non-finite location and/or size for viewport

sessionInfo()

R version 2.8.1 (2008-12-22)
i386-pc-mingw32

locale:
LC_COLLATE=Dutch_Belgium.1252;LC_CTYPE=Dutch_Belgium.1252;LC_MONETARY=Du
tch_Belgium.1252;LC_NUMERIC=C;LC_TIME=Dutch_Belgium.1252

attached base packages:
[1] grid ? ? ?stats ? ? graphics ?grDevices datasets ?utils ? ? methods

[8] base

other attached packages:
[1] ggplot2_0.8.1 reshape_0.8.2 plyr_0.1.5 ? ?proto_0.3-8



------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
Thierry.Onkelinx at inbo.be
www.inbo.be

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of
data.
~ John Tukey

-----Oorspronkelijk bericht-----
Van: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
Namens Avram Aelony
Verzonden: donderdag 26 februari 2009 20:34
Aan: r-help at stat.math.ethz.ch
Onderwerp: [R] bottom legends in ggplot2 ?


Has anyone had success with producing legends to a qplot graph such that
the legend is placed on the bottom, under the abcissa rather than to the
right hand side ?

The following doesn't move the legend:
? ? ? library(ggplot2)
? ? ? qplot(mpg, wt, data=mtcars, colour=cyl,
gpar(legend.position="bottom") )


I am using ggplot2_0.8.2.

Thanks in advance,

Avram