[R] R_Calculating Thiessen weights for an area with irregular boundary

[Manoranjan Muthusamy]

1. Apologies for the lousy presentation of the data and thank you for your
feedback. I promise it will not happen again.

2. Thank you

3. Yes, exactly!

4. Exactly what I wanted without much hassle. Thank you very much. Time to
explore the package 'spatstat'.
    How can I show the Dirichlet tile names (i.e. 1,2,3,....,8) in the plot?

Cheers,
Mano

On Tue, Apr 21, 2015 at 11:33 PM, Rolf Turner <r.turner at auckland.ac.nz>
wrote:

>
> (1) The manner in which you presented your data was a total mess.
> If you ask for help, please have the courtesy to present your data in such
> a manner that a potential "helper" can access it without needing to do a
> great deal of editing and processing.  Like so:
>
> pts <- as.data.frame(matrix(c(415720,432795,415513,432834,415325,
>                               432740,415356,432847,415374,432858,
>                               415426,432774,415395,432811,415626,
>                               432762),ncol=2,byrow=TRUE))
> names(pts) <- c("x","y")
>
> bdry <- as.data.frame(matrix(c(415491,432947,415269,432919,415211,
>                                432776,415247,432657,415533,432657,
>                                415781,432677,415795,432836,415746,
>                                432937),ncol=2,byrow=TRUE))
> names(bdry) <- c("x","y")
>
> (2) Well, at least you presented a usable data set (even though the
> presentation was lousy) which is better than what most posters do.  And you
> asked a "partially" clear question.
>
> (3) I do not know what you mean by "Thiessen weights".  I am guessing that
> these are the areas of the Dirichlet tiles (Thiessen polygons), intersected
> with the "boundary polygon" (i.e. observation window).
>
> (4) If my guess is correct, the following should accomplish the desired
> task:
>
> require(spatstat) # You will (probably) need to install spatstat first.
> W <- owin(poly=bdry)
> X <- as.ppp(pts,W=W)
> plot(X) # Just to make sure it looks right.
> dX <- dirichlet(X)
> plot(dX) # Just to make sure .....
> sapply(tiles(dX),area.owin)
>
> HTH
>
> cheers,
>
> Rolf Turner
>
>
>
> On 22/04/15 02:50, Manoranjan Muthusamy wrote:
>
>  Hi R users,
>>
>> I want to calculate Thiessen weights to compute areal rainfall from number
>> of point measurements. I am using R and thanks to some previous question
>> in
>> the same topic, I got to know that I can usedeldir. But the problem is my
>> boundary polygon is not a rectangle; it's an irregular polygon (it's a
>> catchment boundary derived using ArcGIS). But in deldir the boundary can
>> only be a rectangle. Are there any other packages where I can calculate
>> Thiessen weights of an area covered by an irregular boundary?
>>
>> Given below are my measurement points (meas_points) and coordinates of a
>> (simplified) boundary polygon(boundary)
>>
>>  meas_points
>>>
>>            X      Y[1,] 415720 432795[2,] 415513 432834[3,] 415325
>> 432740[4,] 415356 432847[5,] 415374 432858[6,] 415426 432774[7,]
>> 415395 432811[8,] 415626 432762
>>
>>> boundary
>>>
>>            x      y[1,] 415491 432947[2,] 415269 432919[3,] 415211
>> 432776[4,] 415247 432657[5,] 415533 432657[6,] 415781 432677[7,]
>> 415795 432836[8,] 415746 432937
>>
>> Any help is really appreciated. Thanks.
>>
>
>
> --
> Rolf Turner
> Technical Editor ANZJS
> Department of Statistics
> University of Auckland
> Phone: +64-9-373-7599 ext. 88276
> Home phone: +64-9-480-4619
>

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