[R-sig-Geo] (no subject)

[Jonathan Greenberg]

It seems that a raster-based approach would make more sense, rather than 
the hugely computationally inefficient approach you are suggesting -- 
how about using a least cost path or euclidean distance approach?  Both 
are available in many GIS packages (ArcMap, GRASS GIS, etc...)

--j

x wong wrote:
> dear all,
>
>
>
> I have a raster GIS map converted to points. Now, I am trying to calculate
> the nearest neighbor distance for every point to a cluster of points within
> this map. Since the number of points is more than two millions, I am
> wondering whether there is a computation efficient way to do this.
>
>
>
> The following is what the data looks like:
>
> point_id,x_coord,y_coord,class
>
> 675,-821292,6896866,GL
>
> 738,-819294,6895866,GL
>
> 803,-819294,6894867,GL
>
> 804,-818295,6894867,GL
>
> 805,-817296,6894867,GL
>
> 806,-816297,6894867,RCK
>
> 873,-818296,6893867,GL
>
> 874,-817297,6893867,GL
>
> 875,-816298,6893868,RCK
>
> 876,-815299,6893868,RCK
>
> 877,-814300,6893868,RCK
>
> 878,-813300,6893868,GL
>
> 945,-817297,6892867,GL
>
> 946,-816298,6892868,RCK
>
> 947,-815299,6892868,RCK
>
> 948,-814300,6892868,RCK
>
> 949,-813301,6892868,GL
>
> 950,-812302,6892869,GL
>
> 951,-811303,6892869,GL
>
> 1021,-816298,6891868,RCK
>
> 1023,-814300,6891868,RCK
>
> 1024,-813301,6891869,GL
>
> 1025,-812302,6891869,GL
>
> 1027,-810304,6891869,GL
>
> 1028,-809305,6891870,GL
>
> 1029,-808306,6891870,GL
>
> 1098,-816299,6890868,RCK
>
> 1099,-815300,6890868,RCK
>
> 1100,-814301,6890868,GL
>
> 1101,-813302,6890869,GL
>
> ............................................
>
>
>
> I want to calculate, for example, the nearest distances for all GL points to
> the RCK class.
>
>
>
>
>
> X.W.
>
> 	[[alternative HTML version deleted]]
>
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