Roger,
I got the package. This is great. Thank you very much, I will have a test
run very soon. Have a nice weekend!


X.W.

On Thu, Apr 9, 2009 at 2:42 PM, Roger Bivand <Roger.Bivand@nhh.no> wrote:

> On Thu, 9 Apr 2009, x wong wrote:
>
> I do use Windows, and thank you very much for the help!
>>
>> I know how to do this in GIS as Jonathan suggested; however, I haven't
>> tried
>> it in R with the solution Rick recommended since i am still cleaning my
>> input data.
>>
>> The problem of this task is very obvious: it will be super inefficient if
>> all the distances have to be calculated. My initial thought was to locate
>> the target points and subset the dataset before any calculations being
>> made,
>> but it may require quite a bit coding...... What you described sounds
>> great
>> to me, and i am looking forward to seeing it.
>>
>> b.t.w. the link you provided doesn't work, would you please double check
>> it?
>>
>
> The link works:
>
> http://spatial.nhh.no/R/etc/ann*
>
> means look in:
>
> http://spatial.nhh.no/R/etc/
>
> for all files with names beginning with ann. The build for R 2.8.* is at:
>
> http://spatial.nhh.no/R/etc/ann_0.3-2.zip
>
> You will have to subset your data into two matrices of planar coordinates,
> one matrix for the data= argument, the other for the query= argument to
> ann(). The output object contains the k nearest neighbours in data= for each
> point in query=, and their distances. See ?ann after installing the package.
>
> Roger
>
>
>
>> X.W.
>>
>>
>>
>>
>>
>>
>> On Thu, Apr 9, 2009 at 3:07 AM, Roger Bivand <Roger.Bivand@nhh.no> wrote:
>>
>> On Wed, 8 Apr 2009, x wong wrote:
>>>
>>> Thank you very much, that is very helpful.
>>>
>>>>
>>>>
>>>> x.w.
>>>>
>>>> On Wed, Apr 8, 2009 at 12:47 PM, rick reeves <reeves@nceas.ucsb.edu>
>>>> wrote:
>>>>
>>>> Assuming that this dataset fits within the confines of R, this could be
>>>>
>>>>> done with sp package:  spdistsN1() function
>>>>> See attached sample solution:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> http://nceas.ucsb.edu/scicomp/GISSeminar/UseCases/AssignClosestPointsR/AssignClosestPointsR.html
>>>>>
>>>>> Hope this helps! RR
>>>>>
>>>>>
>>>>> Note that this will be inefficient in that it calculates all the
>>> distances.
>>> I have an off-CRAN package interfacing ANN, which - given two sets of
>>> points, returns the k nearest in the first set (with distances) for each
>>> point in the second set. ANN builds a tree of the first set, so searches
>>> for
>>> nearest neighbours efficiently. Look for:
>>>
>>> http://spatial.nhh.no/R/etc/ann*
>>>
>>> The Windows binary wasn't built for the current release of R, so probably
>>> needs rebuilding - let me know if you use Windows, and I'll re-build it.
>>>
>>> Hope this helps,
>>>
>>> Roger
>>>
>>>
>>>
>>>  Jonathan Greenberg wrote:
>>>>>
>>>>> 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]]
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> R-sig-Geo mailing list
>>>>>>> R-sig-Geo@stat.math.ethz.ch
>>>>>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>>
>>>>>> R-sig-Geo mailing list
>>>>>> R-sig-Geo@stat.math.ethz.ch
>>>>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>>>>>
>>>>>>
>>>>>>
>>>>> --
>>>>> Rick Reeves
>>>>> Scientific Programmer/Analyst and Data Manager
>>>>> National Center for Ecological Analysis and Synthesis
>>>>> UC Santa Barbara
>>>>> www.nceas.ucsb.edu
>>>>> 805 892 2533
>>>>>
>>>>>
>>>>>
>>>>>       [[alternative HTML version deleted]]
>>>>
>>>> _______________________________________________
>>>> R-sig-Geo mailing list
>>>> R-sig-Geo@stat.math.ethz.ch
>>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>>>
>>>>
>>>> --
>>> Roger Bivand
>>> Economic Geography Section, Department of Economics, Norwegian School of
>>> Economics and Business Administration, Helleveien 30, N-5045 Bergen,
>>> Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
>>> e-mail: Roger.Bivand@nhh.no
>>>
>>>
>>>
>>
> --
> Roger Bivand
> Economic Geography Section, Department of Economics, Norwegian School of
> Economics and Business Administration, Helleveien 30, N-5045 Bergen,
> Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
> e-mail: Roger.Bivand@nhh.no
>
>

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