[R] Using factor levels as coordinates with geom_rect

Loris Bennett loris.bennett at fu-berlin.de
Tue Sep 23 09:05:36 CEST 2014


With ggplot2 I can use the following to create a rectangle 

geom_rect(aes(ymin=as.Date("8-Apr-2014", format="%d-%b-%Y"),
                ymax=as.Date("30-Apr-2014", format="%d-%b-%Y"),

where the x values are levels of a factor.  This works if I want the
rectangle to extend across a range of factor level.  My question is this:

How can I create a similar rectangle around a single factor level?

My assumption is that I should be able to convert the factor to a
numerical value.  I could then subtract and add a smaller number to
obtain xmin and xmax, respectively.  However, I don't know how to
convert the factor level to a value which corresponds to its
x-coordinate on the plot.

I posted a longer version of this question on StackOverflow with the
full code, input data, and a plot of the output:


Unfortunately, I didn't get an answer.



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