I created the plot with ggplot2 and, among other things,
geom_point(). The PDF looked fine when viewed in OS X's Preview
application but when I imported the plot into Inkscape all of my
points became the letter "q".
My first thought was to manually change the q's back to points in Inkscape. Then I came to my senses and thought that surely I wasn't the first person to run into this problem. A quick Google search showed that I wasn't.
It turns out that when exporting to PDF, R may use glyphs from
the Dingbat font set for plot elements. Luckily, this can
be prevented by setting the
FALSE. For example,
I re-created the PDF with this option setting, imported it into Inkscape, and basked in the glory of a properly imported graphic.
If you're curious about the plot itself, I plan to discuss it in a future post. As a teaser, I'll just say that I had to dust off my trigonometry brain cells and learn a bit more about map projections.