output to graphviz .dot
just in case anyone runs into the same problem:
the docs say nothing about how to specify the output to a pure .dot file -- the trick is to pass it the -o param with output filename ending with .dot as well as using the -z option.
(defaults to .gif for -z -- can also use this method for any other (man dot) compliant formats (png,etc)
An open, cross-platform journaling program.
A scientific plotting package.