r - Outlined text with ggplot2

Question

I'd like to know if there is a way to draw "outlined text" with ggplot2, for example black text with a small white border, in order to make it easily readable on backgrounds such as maps.

Ideally I'd like to achieve the same type of labels you can see on Google Maps :

Thanks in advance for any hints !

question from:https://stackoverflow.com/questions/10686054/outlined-text-with-ggplot2

Answer 1

Here is an approach that implements the general idea from the shadowtext function in the TeachingDemos package. The code for the middle part could be wrapped into a function to simplify some things. The example is blatantly stolen from Richie Cotton's answer:

d <- diamonds[sample(nrow(diamonds), 10), ]  


p <- ggplot(d, aes(carat, price) ) 
theta <- seq(pi/8, 2*pi, length.out=16)
xo <- diff(range(d$carat))/200
yo <- diff(range(d$price))/200
for(i in theta) {
    p <- p + geom_text( 
        bquote(aes(x=carat+.(cos(i)*xo),y=price+.(sin(i)*yo),label=cut)), 
                    size=12, colour='black' )
}
p <- p + geom_text( aes(label=cut), size=12, colour='white' )
p <- p + opts( panel.background=theme_rect(fill='green' ) )
print(p)