[postgis-users] Creating density map

[Aren Cambre]

I have three datasets:

   1. Routes
   2. Event type A that occurs along the routes (points)
   3. Event type B that occurs along the routes (points)

Both event types have several attributes, including a date/timestamp,
sub-classes of each event type, and other meaningful attributes.

I'm trying to use statistical methods to check for certain relationships
between event types A and B. They may influence each other (A may affect B
and B may affect A). I also want to see if there's a relationship between
subtypes. E.g., do events A.X or A.Y have a stronger impact on event type B?

I'd like to make heat density maps to help interpret the data, but I have
two conceptual problems.

*First problem is how to make the map.* The programmatically easy but slow
way is to create a greedy algorithm to traverse every route. During
traversal, create a point at each increment of distance X. An attribute of
that point may be the number of qualifying events no more than distance Y
from that point.

I may need to limit to events along the route I am traversing. E.g., if
traversing route M looking for event type B, and I come across route N, the
heat map for route M probably should not include events of type B along
route N event if they are within Y distance from my current point.

*Second problem is how to deal with all the permutations. *I could muck
through the simple algorithm and make spiffy point maps, and with a little
graphical wizardry, I could make the maps pretty. However, I need to do
analysis over different time periods. E.g., does the relative intensity of
week I's event type As along route M affect the occurrence of event type B
on week I+1? How about event type A.X? A.Y? Do they have different effects
over the same time period? I have between 3 and 9 years of event types A and
B...

All the permutations (not simply combinations) of factors can really explode
the complexity of this project.

To prevent wheel reinventing, are there already well-tread solutions to this
problem? I've done some Google searches and am not coming up with much, so I
guess I may not be using the correct lingo?

I know that I need to incorporate R into this at some point; my objective
now is to get the data to a point where I *could* use R to analyze it.

Aren
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