Request: parse expressions for geom_dl()

[eggrandio]

Hi,

I was wondering if there is a way of parsing expressions to use as direct labels. For example, to use superscript, having test1^test2 as label would be plotted as test1^test2. ggplot2 geom_text has a parse option that if set to TRUE will parse expressions.

For example, ggrepel has the parse flag to use expressions, but you have to "hide" the unwanted labels and leave only one per group to be able to do the same as with a directlabel. If I have to do this for different plots, with different groups, it is almost impossible to always select the point with the most optimal label placement.

See also this question in stackoverflow.

[tdhock]

Hi @eggrandio that sounds like a useful feature, that is currently not supported by directlabels.
If you would like to implement it, I would consider a PR.

[tdhock]

a work-around which I use to achieve the same effect (math in direct labels) is using tikzDevice, for example

gg <- ggplot()+  
   ...
    directlabels::geom_dl(aes(
        change, cost_candidates,
        color=Algorithm,
        label.group=Algorithm,
        label=sprintf("$\\tau^*_{%d} = %d$", up.to.t, tau)),
        method="bottom.polygons",
        debug=TRUE,
        data=COST(cost.dt))
    tikzDevice::tikz("tikz-graphics.tex", width=5.4, height=2.5)
    print(gg)
    dev.off()

taken from https://github.com/tdhock/LOPART-paper/blob/master/figure-candidates.R makes
these slides https://github.com/tdhock/LOPART-paper/raw/master/slides.pdf with images like this