On 18/03/2010, at 12:25 PM, Tom_R wrote:
>
> Hi,
> How do I use nncross to measure min distances between point patterns i,j,
> ENSURING each point in pattern i is only connected to a single partner
> point in pattern j ?
> I do realise that there are many possible pairings between the i-j point
> pairs... perhaps some average min distance for many pairings would be
> better. Alternatively pairings could be randomly assigned.
>
> Basically, i am tracking a population of moving objects over time, and want
> to indirectly estimate the collective movement- which might be better
> estimated by telling nncross to randomly assign (somehow) paired nearest
> neighbour distances ; 1-to-1 rather than many-to-one.
This is a question about the spatstat package and as such should be directed
to the maintainers of the package, rather than the list. (Unless a response
cannot be evoked from the maintainers.) See the Posting Guide.
Having said that --- I'm afraid that I don't understand your question.
If you do
nncross(X,Y)
where X and Y are point patterns (``i'' and ``j'' suggest indices and as such
are not good names for point patterns) you get a vector of distances which are
the distances from each x in X to its nearest neighbour in Y. Thus you get
the minimal distance from each x in X to the pattern Y. There are no multiple
pairings to worry about. If you *want* all possible distances you could use
crossdist() --- and then average these distances by using apply() on the
result.
If this doesn't answer your question, can you please clarify your question?
cheers,
Rolf Turner
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