[Mapserver-users] Using MapServer as a general graphing engine

[Mishtu Banerjee, SCIENTIFICALS]

There's a small set of 2D graphs that are very commonly used in data
analysis -- and if they could be represented in mapserver -- one would be
able to do a lot of visual statistical analysis:

1. Visualizing Location: These are things like "BoxPlots" or "Bar and
Whisker" Plots.
2. Visualizing Spread: These are things like a simple X, Y scatter --
Tyler's example is X,Y data, as
two variables. But say you have multiple variables -- you can do a series of
2X2 scattergrams. Often you can draw an ellipse around the x,Y scatters to
represent the spread.
3. Visualing Distribution. Histograms, cumulative frequency diagrams.

Location, Spread, Distribution in simpler or fancier forms are the guts of
most data analysis. Stats programs (such as Systat) of course have a way of
dealing with these things, in the non-spatial realm; but can't handle
spatial data well. So, is it possible to have a system that handles spatial
well, also handle non-spatial in terms of cartesian space?

In terms of geometry, from a data visualization point of view, you're
working in cartesian space -- and could be said to be providing various maps
of the space. A scattergram is like locating points. A BoxPlot could be seen
as a kind of standard polygon shape, that will be scaled based on the
statistics, and located based on the X,Y midpoints.

If you had the ability to incorporate this into MapServer as 2D displays,
MapServer would morph into a Visual Stats Server. :-)

-- mishtu

-----Original Message-----
From: Tyler Mitchell [mailto:TMitchell at lignum.com]
Sent: Monday, July 28, 2003 12:02 PM
To: mapserver-users at lists.gis.umn.edu
Subject: Re: [Mapserver-users] Using MapServer as a general graphing
engine







I'm thinking more along these lines:

- I have x,y data where these are two non-geographic values that I want to
graph.  I have z which is the magnitude, count, etc. that I want to graph.
- Use a simple coordinate system to map the "location" of the x,y pairs and
draw the symbol based on the z value.
- z may be a value used as a radius for a circle or there may be a z- and
z+ which defines the vertical offsets of the extents of a bar/rectangle.

So I'm not so concerned with bringing in pre-made maps, as I am about
generating maps using non-spatial data.   Of course, sometimes "z" may be
an image but I wasn't thinking that far ahead.

Tyler

Armin Burger <armin.burger at libero.it> wrote on 07/28/2003 12:53:53 PM:

> Tyler,
>
> I also found it sometimes desirable to have Mapserver create thematical
> maps with pie charts or bar charts, etc. I don't know how much work it
> might be to implement this. Maybe DM Solutions OWTChart could be somehow
> included?
>
> Another, probably a bit easier implementation, could be using MapScript
> combined with graphic modules/extensions for Perl or PHP, mainly based on
> the GD library. But as far as I know there is no possibility to include
> externally produced images and merge them on top of the map image. A
> question to the developers: would it be possible to have a Mapscript
> method that creates an imageObj from a file?
>
> This way one could create all the charts based on shapefile or database
> data with external graphic functions and merge these images with the map
> image using the existing 'pasteImage' method. For not too many charts the
> speed should be acceptable. For placing a chart exactly over a polygon a
> method to calculate the shape centroid would be helpful.
>
> Could this approach make sense?
>
> Armin
>
>
>
> > I know that a ton of web-based options exist for graphing and charting.
> > But very few seem to really understand spatial data and many have a
> > narrower scope of data sources than MapServer has.
>
> > Am I the only one interested in doing this or are you interested in
> doing
> > this as well.  I see a few queries on related topics in the archives,
> but
> > very few responses.  So I am writing now to gather a feel for the level
> of
> > interest that others on the list may have to do all sorts of graphing
> and
> > charting stuff all within MapServer's capabilities.
>
> > Tyler
>
> > _______________________________________________
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> > Mapserver-users at lists.gis.umn.edu
> > http://lists.gis.umn.edu/mailman/listinfo/mapserver-users
>