After some very brief web searching, I have reached the conclusion that it is currently not possible to apply cross-hatching effects to the fill in a ggplot.
My rather crude solution was to add this in a graphics package1. Selecting each of the bars, including the box within the key, then applying a “half-tone” filter in a new layer. Once the effect is applyed the opacity can be reduced in the hatching layer.
The figure above will appear in [Blythe et al., 2016]2.
References
Blythe, J., Mardigan, K. C., Perdjert, M. E., and Stoakes, H. (2016). Pointing out directions in Murrinhpatha. Open Linguistics, In Press.
-
I used Pixelmator on OS X but any similar tool would work ↩
-
I am investigating ways to parse references but this was inserted manually. ↩