[R] confine a dataframe with a polygon

[temiz]

Roger Bivand wrote:
> On Tue, 3 Apr 2007, temiz wrote:
>
>   
>> hello
>>
>> how can I confine a dataframe with a known polygon that is part of whole 
>> data ?
>>     
>
> Could I suggest following up this question on the R-sig-geo list? It is 
> not clear what you want to do - are the rows in the data frame points 
> which may lie inside or outside a polygon? If so, the overlay() methods in 
> the sp package may be suitable.
>
>   
>> regards
>>
>>
>>     
>
>   
thank you for your reply

I have not been aware of  that list (R-sig-geo list)
My data is elevation point data in a text file.
I want to create DEMs with different interpolation
methods for comparision.
Actually I created DEM in GRASS using spline tension.
Then I want to create DEM in R with different techniques to compare.
But my data seems so huge for GSTAT-kriging and FIELDS-krig.
So I decided to select smaller interpolation area within whole data.

How can I define a subregion in which I do interpolation ?

I found locator and chull function that may serve this.

I will regard your recommendations.

PS : Thinking facing a memory problem, I refrained from GRASS-R interface.



-- 
Ahmet Temiz


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