Using geom_line and geom_point with only one legend.

[Manuel Holtgrewe]

Hi,

is it possible to create a plot with both lines and points and have
only one legend?

Currently, I use the following to create my plot:

p <- ggplot(molten.data, aes(x=max_errors, y=value, colour=mapper,
group=mapper, shape=mapper), summary="asdf")
p <- p + facet_wrap(~ variable, scales="free_y", ncol=1)
p <- p + geom_line()
p <- p + geom_point()
p <- p + scale_x_discrete(name='max error')
p <- p + scale_y_continuous('')
p <- p + scale_colour_discrete('read mapper')
p <- p + theme_bw()

The plot looks allright, there are markers at my data points and
lines connecting them. However, there is a key for both data points
with the right shape (all black) and one for the lines with the right
color (but the wrong shape). Is there a way to "merge" the legend?

[hadley wickham]

Hi Manuel,

Can you please provide a reproducible example by including some of
your data with dput?

Hadley

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[Brian Diggs]

On Feb 19, 4:22 am, Manuel Holtgrewe <zyklenf...@googlemail.com>
wrote:

> Hi,
>
> is it possible to create a plot with both lines and points and have
> only one legend?

Legend merging happens automatically when they have the same title and
level labels (it may be more complicated than that, but this is the
general idea; see Section 6.5, p111 of the ggplot2 book, if you have a
copy of that).

> Currently, I use the following to create my plot:
>
> p <- ggplot(molten.data, aes(x=max_errors, y=value, colour=mapper,
> group=mapper, shape=mapper), summary="asdf")
> p <- p + facet_wrap(~ variable, scales="free_y", ncol=1)
> p <- p + geom_line()
> p <- p + geom_point()
> p <- p + scale_x_discrete(name='max error')
> p <- p + scale_y_continuous('')
> p <- p + scale_colour_discrete('read mapper')

You changed the name of the colour scale, but not the shape scale.
Change the shape scale as well and they should merge. (Untested, since
you don't have a self-contained example).

p <- p + scale_shape_discrete("read mapper")

> p <- p + theme_bw()
>
> The plot looks allright, there are markers at  my data points and
> lines connecting them. However, there is a key for both data points
> with the right shape (all black) and one for the lines with the right
> color (but the wrong shape). Is there a way to "merge" the legend?

--Brian Diggs

[Manuel Holtgrewe]

Thanks, that worked fine.