Re: geographic plotting

[Ethan A M. <me...@uw...>]

On Tuesday, 3 March 2020 17:05:40 PST Allin Cottrell wrote:
> On Tue, 3 Mar 2020, Ethan A Merritt wrote:
> 
> > On Tuesday, 3 March 2020 14:30:40 PST Allin Cottrell wrote:
> >> This question has been posed before (a few years back) but I'm
> >> hoping someone may be able to point me to the state-of-the-art,
> >> if there is such.
> >>
> >> I'd like to be able to produce via gnuplot a map of (for example)
> >> the USA showing the states colored by median income, or PM2.5
> >> particulate emissions, or whatever.
> >>
> >> I understand that the starting point would be a suitable US states
> >> shapefile (I know where I can get that), which would have to be
> >> translated to a format (resembling world.dat, I suppose) that can be
> >> understood by gnuplot. I have some notion of how that might be done.
> >>
> >> The next issue would be to get gnuplot to colorize specified areas
> >> of the map according to the values of some additional data.
> >> Unfortunately I have little notion of how to do that.
> >
> > The development version of gnuplot supports
> >
> > 	splot <data> with polygons
> 
> Thanks Ethan, and also Dima in this thread. This sounds promising!
> Right now I'm not sure when I'll find time to pursue this in depth, 
> but I'm definitely interested and will push it when I can.
> 
> Allin Cottrell

This may be putting the cart before the horse, but...
Do you think it would be helpful to teach gnuplot to read shape files?
I imagine it would be possible to test for the presence of shapelib.so
and provide a binary input mode:

   splot <data> binary filetype=shapelib  with polygons

I have never worked with this libary so I don't know if it is organized
in such a way that this would be possible.

A quick look at the spec for the shapefile format makes it look horrible
(mixed little-ending big-endian in the same file?! variable record types
that are required not to vary?!),  but if it is hidden by a usable library ....

	Ethan