Plotting tables with DrRacket has been teaching me a lot. It felt wrong to go out of DrRacket and into the shell just to montage (ImageMagick) the row-based and column-based plots together. Racket features plot-pict so it seemed like the right time to start learning the pict library.(fn:1) With picts I was able to vc-append a gray separator between the two plots, and to add pip-arrows-lines to point out connections between the two views.

The plots I work with can become long images. Long picts are awkward to work with in DrRacket. I could only scale to the top, and could not check the lower part of the plot. Enclosing the pict code withpict->bitmap makes iterative development smoother. A bitmap is much easier to scroll in DrRacket.

It took a few attempts to learn how to save the pict->bitmap images to file. I was looking for a basic Scheme-like approach with open-output-file or with-output-to-file but nothing worked. The task of saving plot-pict bitmaps as png files has become my introduction to objects in Racket. You send an object a method and arguments. It didn't make sense to me until reading the ambiguous sentence I just typed. With send you don't send the very next expression somehwere, you send the following expressions to the next expression. So send's second argument (if you see send as a typical Racketfunction) is what gets the rest of the arguments.