Re: netCDF & SpreadSheet question; visualising a network structure

• To: visad-list@xxxxxxxxxxxxx
• Subject: Re: netCDF & SpreadSheet question; visualising a network structure
• From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>
• Date: Tue, 06 Jul 1999 13:28:14 -0500

Hi Armin,

> my apologies if I miss the obvious, but how do I use the netCDF
> file format to save a datastructure like that: I have a set of
> n nodes and for each node I have a list of ingoing edges and
> outgoing edges.  The best way to think of it, is like the internet.
> I have a set of routers and for every router a list of other routers
> connected to it. How do I save sth. like that easily in netCDF?

VisAD expresses network data as the topologies of irregular
Sets.  Unfortunately, the edges are not directed and such
data cannot be saved to netCDF files (at least not as Set
topologies).  You could convert this data to a FlatField
with MathType:

  (edge_number -> (in_node_number, out_node_number))

where all the values are constrained to be integers, and then
save this to netCDF.  However neither netCDF nor VisAD would
interpret this data with any network semantics.  To display
this data, you'd need to convert it to a Set topology, as ...

> Suppose I use the SpreadSheet prg. to display my datastructure,
> I map the x,y,z coordinates of the nodes of  the X,Y and Z
> coordinate. How can I tell SpreadSheet to draw a straight line
> to connect some of my nodes, which I specify?

You can construct an arbitrary network using the DelaunayCustom
class (however there is no way to indicate the directions of
lines connecting nodes).  Then you can adapt the code in
Delaunay.main() (from lines 823 to 997) to convert your
'Delaunay delaun = new DelaunayCustom(...)' into a UnionSet
of Gridded3DSets (with manifold dimension = 1) for display.
Note this code also generates numerical text labels for the
edges, which you might want to discard.  Sorry we don't have
a neater answer for you at this time.

Cheers,
Bill
----------------------------------------------------------
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
http://www.ssec.wisc.edu/~billh/vis.html