More work on the script, too - got it to get rid of the linebreaks (thanks marnanel :) ), got it to handle 0 and empty fields differently (thanks jarel, who also figured out why some of the empty fields were empty & some were undefined :) ). And got it to draw some proof of concept Max/Min graphs, of which this is a representative sample:
Obvious flaws - needs scale marking, it's too small, colour choice sucks. But hey, it's a graph! ;) J had to help me figure out some stuff, and I really seriously need to tidy up & abstract the code that draws it coz it's full of numbers (which I found easier to follow at the time but later it's going to be an incomprehensible mess and changing anything is tedious). It's progress though and once I figure out one set of graphs there's several subsets of the data that I can represent with not much more work.