R help - Jun 2008 - ggplot2: How to remove legend component for geom_errorbar() ?

Dear list (probably Hadley),

I'm trying to do a plot like the following, composed of bars and error
bars:

df <- data.frame(factor1=gl(2,5), factor2=gl(5,1), y=rnorm(10),
err=0.1) 
ggplot(df, aes(x=factor1, y=y, fill=factor2)) +
    geom_bar(position="dodge", stat="identity") + 
    geom_errorbar(aes(min=y-err, max=y+err), position="dodge",
width=0.1)

The plot obtained has a legend named "factor2", giving as expected the
colours used for the five factor levels of factor2. So far so good.
However, the legend also contains solid horizontal lines, obviously
representing the error bars. While I do not immediately see the sense of
a legend symbol for error bars, is there any easy way to turn these off?

Thanks,
Carsten

Hi Carsten,

In my eagerness to get every component of the legend working
automatically, I've completed neglected a way to turn bits off of you
don't want them (the philosophy is that every geom that uses an
aesthetic should appear in the legend in some way).  The best thing I
can suggest at the moment is:

GeomErrorbar$guide_geom <- function(.) "point"

to use points for the errorbar legend, which you won't see because
they'll overlap with the points from the points geom.  In the next
version, you'll be able to do

GeomLine$guide_geom <- function(.) "blank"

Or I might come up with a better way of controlling the appearance.

Regards,

Hadley

On Mon, Jun 16, 2008 at 2:55 AM, Carsten Jaeger <cajaeg at googlemail.com>
wrote:
> Dear list (probably Hadley),
>
> I'm trying to do a plot like the following, composed of bars and error
> bars:
>
> df <- data.frame(factor1=gl(2,5), factor2=gl(5,1), y=rnorm(10),
> err=0.1)
> ggplot(df, aes(x=factor1, y=y, fill=factor2)) +
>    geom_bar(position="dodge", stat="identity") +
>    geom_errorbar(aes(min=y-err, max=y+err), position="dodge",
> width=0.1)
>
> The plot obtained has a legend named "factor2", giving as
expected the
> colours used for the five factor levels of factor2. So far so good.
> However, the legend also contains solid horizontal lines, obviously
> representing the error bars. While I do not immediately see the sense of
> a legend symbol for error bars, is there any easy way to turn these off?
>
> Thanks,
> Carsten
>
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