I’m (usually) a fan of the R programming language, though in a few ways it lacks features computer scientists expect. For example, R lacks many data structures provided by high-level languages, such as trees, queues, and stacks. This is somewhat complicated by R’s functional nature–R programmers expect data structures to be “persistent,” such that previous versions of the structure are available even after insertions or deletions. Fortunately, data structures in purely-functional languages (generally not R) is a topic of past and ongoing research, spurred initially by Chris Okasaki’s excellent Purely Functional Data Structures. THis implements purely functional stack and queue data structures as described by Okasaki and others, and gives examples of their use, in R. The package, rstackdeque, is available on CRAN, and described in the R Journal.
Combined with ggplot2, it provides a nice way to visualize recursive processes.
