[Qgis-user] nearest point selection without reuse

[Rainer M Krug]

On Fri, Mar 26, 2010 at 5:01 PM, M.E.Dodd <m.e.dodd at open.ac.uk> wrote:

> Is it possible to find the nearest point in one table compared to points in
> another table BUT without using the same point in the second table more than
> once.
> I have one table of points and want to find the nearest point in another
> table, the trouble is that some points in the second table are used many
> times and others are not used at all even though they are only slightly
> further away.  There are different numbers of points in each table, each
> table has hundreds or thousands of points.  The multiple use of points in
> the second table like this might be biasing the analysis.
>

Effectively, an iterative process should work (although I am not sure you
can do it with QGIS).

Effectively, you have to eliminate the point from dataset two after it is
identified as "nearest point" to one in dataset one. But there is one aspect
you have to consider: there will be more then one solution, and you have to
decide, which one you want to choose - shortest sum of distances possibly?
In addition, you will get different solutions, depending on which point in
dataset one you begin with.
So effectively:
yes, it is possible
but you have to define your problem more accurately
and it requires an iterative approach, with (likely) an optimisation
I don't know if it can be done in QGIS.

Cheers,

Rainer


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