[R-sig-Geo] Question for point pattern experts

[Rolf Turner]

On 11/02/2011, at 6:00 AM, david depew wrote:

> Dear list,
> A brief and (hopefully) simplistic question regarding point pattern
> analysis.
>
> We have compiled a large, continental database of chemical burdens  
> in a
> model organism. Currently, the data span 40 years and covers the  
> entire
> country of Canada (including the high arctic). We have categorized the
> numeric data into categorical data (i.e. categorical marks) based  
> on risk
> thresholds. We'd like to assess whether or not there are  
> interesting spatial
> patterns ( i.e. clusters of levels of risk (high vs low)), much like a
> case/control approach. My question is as follows;
>
> Is there a "best" geographic projection for this approach?  
> Currently all
> data are in Latitude/Longitude. My inclination is to use something  
> along the
> lines of an equal area projection to maintain a reasonable  
> representation of
> spatial dispersion.

This doesn't sound to me like ***point pattern*** data.  It sounds like
you have taken measurements of ``chemical burdens'' in a particular
organism, at a number of ***chosen*** sites over a number (40) of years.

Thus the observation points are deterministic, not random, and so point
pattern analysis doesn't come into it.

It may be the case that some sort of combination of kriging and time  
series
or repeated measures analysis might be called for.  But here I speak of
that of which I know nothing.

	cheers,

		Rolf Turner