Background: the directlabels package facilitates use of direct labels instead of legends in everyday statistical graphics made with lattice or ggplot2. Labeling is currently limited to textual annotations, but sometimes it is more informative to label using images, i.e. iris data labeled with photos of the 3 flower species or scatterplot comparing several countries using their flags

Goal: develop a framework for labeling plots using images instead of textual factor names. There is some preliminary code, but there are a few technical problems with plotting images in R that must be overcome:

• SVG vector graphics using grImport
  • How to import SVG into R in a portable manner? Currently I use a python script to convert SVG to PS, then use grImport to read PS images.
  • Some complicated PS images cause errors in grImport::PostScriptTrace() when attempting to convert to RGML, i.e. http://upload.wikimedia.org/wikipedia/commons/d/da/Flag_of_Kansas.svg
  • Some PS images are convered to RGML but then plotted incorrectly, i.e. http://upload.wikimedia.org/wikipedia/commons/0/01/Flag_of_California.svg
  • Possible solution: convert SVG images to hi-res raster graphics?
• JPG raster graphics using EBImage
  • High-resolution JPG images take a long time to read into memory, and create huge files when making R plots using the pdf() device. i.e. 20MB pdf for this plot of the iris data. Can we compress the images plotted with grid.raster?
  • Possible solution: just don’t use the pdf device? jpg and png images created in this way are of decent size.

Tests:

• To see how to direct label using textual annotations, make some direct labeled plots using the lattice, ggplot2, and directlabels packages.
• To explore the current state-of-the-art in importing images into R, make some plots that use vector images using the grImport package, and raster graphics using the EBImage package.
• To demonstrate basic knowledge of SVG and PS syntax and semantics, make a PS or SVG plot using R, then MANUALLY edit the PS or SVG file to make a modification of the plot.

Mentors: Toby Dylan Hocking toby.hocking@inria.fr, Paul Murrell p.murrell@auckland.ac.nz