On 2012-10-02 22:24-0400 Hezekiah M. Carty wrote:

> I've used PLplot to plot a lot of data on maps, including mixing data
> from shapefiles and other sources.  Based on my experience I think we
> may be going off in the wrong direction here.

Hi Hez:

In order to be sure we understand the rest of your comments, could you
explain in more detail how you made map data accessible to PLplot so
you could decorate existing maps like you described above?  I assume
your applications used the API of libraries like shapelib, MDAH, and
OGR to import the map data you desired and then you called on the
libplplot routines to manipulate those data further, but that
assumption needs confirmation.

If you do confirm that was the approach you took, my vision is quite
similar except my idea was it would be an added convenience for many
map/PLplot users to provide a PLplot API that imports map data so their
applications can manipulate those data with further PLplot commands.
Of course, if some users didn't like that PLplot map importing API,
they would be free to import map data into their applications in any
other way they like, but our job would be to make that PLplot map
importing API reasonably attractive and useful for a large majority of
users' map importing needs without making that API too complicated.

If you respond you cannot simplify the shapelib, MDAH, and OGR API's
any more than they are now for PLplot's _limited_ needs, then
obviously it makes little sense for PLplot to provide duplicates of
those map importing API's when the user can just call those libraries
directly from his application.

However, private map importing functionality _is_ needed behind the scenes for
plmap (as used in example 19), and I think we should support that "hidden"
approach (where the map data is simply plotted and not exposed to the
calling routine) as well as the "exposed" approach (which does
expose the map data to the calling routine) as outlined above.

As we all know, the map importing that plmap does behind the scene
currently uses an obscure map file format with very few maps
associated with it, but I think we should expand that map importation
capability along the lines I described above for the "exposed"
approach.

Would a good compromise be to work exclusively on improving the map
import capability behind plmap for now?  If it turns out we like how
we simplify the shapelib, MDAH, and OGR API's in that private case for
plmap's limited map import needs, then we can turn that into a general
public API suitable for the "exposed" case described above.  But if
the improved map importing functionality we develop for plmap is not
going to be added value for users (say, because it just duplicates
shapelib, MDAH, and OGR API's) then we should keep it private for the
exclusive use of plmap.

I certainly agree with you that we need examples of the "exposed" case
(whether implemented with direct calls to shapelib, MDAH, or OGR or
via some PLplot map import API if that turns out we develop that). I
haven't thought too much about your call for improvements in PLplot's
functions to deal with additional general plotting needs that would be
useful for the "exposed" map case, but I assume those ideas are well
taken as well.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
__________________________

Linux-powered Science
__________________________

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