[R-sig-Geo] Problems with Kcross.inhom
Marcelino de la Cruz
marcelino.delacruz at upm.es
Tue Oct 22 18:21:07 CEST 2013
It seems that you get an estimate of lambda= 0.00000 for your ficus
point #2. Kinhom can only be estimated when lambda > 0 in all points.
I would use either another sigma for bandwith estimation or set the
argument leaveoneout=FALSE.
Cheers,
Marcelino
El 22/10/2013 14:37, David Villalobos escribió:
> Hi Rolf and Julia
>
>
> Many thanks for your help, I appreciate that. I am sorry for the
> inconvenient, I am new in these things.
>
>
> Just to clarify, my window is complex because is created from a
> "shapefile" that delimit my study area. This study area (called "W" in
> the analysis) have the spatial locations of my data ("ficus" and "tienda").
>
>
> With the purpose of reproduce the analysis and try to find the problem,
> in the attachment documents you can find the "shapefile" of my study
> area, a "txt" document of my data and my R script (Kcrossinhom(DV)).
>
>
> Again, I really appreciate your help. Thank you.
>
>
> Cheers
>
>
>
> 2013/10/21 Julia Chacon Labella <juliachacon at gmail.com
> <mailto:juliachacon at gmail.com>>
>
> Yes, I tried to reproduced your example, and I didn´t have any
> problem. Have you check how are your lambdas?? Why are you using "at
> points" instead of the default "by pixel"??
>
> It seems that could be the lambda values what is wrong. Try to
> visualized them, and try with the pixel image.
>
> Other option is to built a new window for your pattern. How did you
> built it?
>
>
>
> 2013/10/22 Rolf Turner <r.turner at auckland.ac.nz
> <mailto:r.turner at auckland.ac.nz>>
>
>
>
> Again, your problem is not reproducible. We do not have the objects
> "north", "west", "W" and "tipo" which are necessary to duplicate
> your
> steps.
>
> I tried to reproduce your problem with an artificial example:
>
> W <- owin(c(0,3350),c(0,6150))
> set.seed(42)
> Z <- runifpoint(201,win=W)
> m <- sample(rep(c("ficus","tienda")__,c(131,70)),201)
> marks(Z) <- factor(m)
> ff <- with(split(Z),bw.diggle(ficus)__)
> tt <- with(split(Z),bw.diggle(__tienda))
> lambdaf <- with(split(Z),density(ficus,__ff,at="points"))
> lambdat <- with(split(Z),density(tienda,__tt,at="points"))
>
> K <- Kcross.inhom(Z,"ficus","__tienda",lambdaf,lambdat)
>
> No problema.
>
> It is possible that the error has something to do with the
> rather intricate
> (1716 vertices) boundary of your observation window. However
> since I don't
> have that window I can't tell.
>
> cheers,
>
> Rolf Turner
>
>
>
> On 10/22/13 10:16, david.villalobos wrote:
>
> Sure Julia,
>
> First:
>
> I have the following object called "Z"
>
> Z <- ppp(north, west,window=W,marks=tipo)
> summary(Z)
>
> Marked planar point pattern: 201 points
> Average intensity 4.46e-05 points per square unit
>
> Coordinates are integers
> i.e. rounded to the nearest 1 unit
>
> Multitype:
> frequency proportion intensity
> ficus 131 0.652 2.90e-05
> tienda 70 0.348 1.55e-05
>
> Window: polygonal boundary
> single connected closed polygon with 1716 vertices
> enclosing rectangle: [484546.8, 487897.4] x [1147521.3,
> 1153682.9] units
> Window area = 4509680 square units
>
> Second:
>
> I calculated the bandwidth sigma for the kernel estimator of
> point process
> intensity with a Cross Validated Bandwidth Selection for
> Kernel Density
> (bw.diggle)
>
> attach(split(Z))
> f<-bw.diggle(ficus)
> t<-bw.diggle(tienda)
>
> Third:
>
> I calculated with the Kernel Smoothed Intensity of Point Pattern
> (density.ppp) the values of the the estimated intensity of
> the sub-process
> of points of type i and j:
>
> lambdaf<-density.ppp(ficus,f,__at="points")
> lambdat<-density.ppp(tienda,t,__at="points")
>
> and Finally:
>
> I ran the script for Kcross.inhom for the method (1):
> estimate intensities
> by nonparametric smoothing, but I had the error.
>
> K <- Kcross.inhom(Z, "ficus", "tienda", lambdaf, lambdat)
>
> Error in Kwtsum(dclose, bI, weight, b, 1/lambdaI, breaks) :
> Weights in K-function were infinite or NA
>
> I tryed the method (2): leave-one-out, but I had the same
> problems
>
> Any help is appreciated. A lot of thanks.
>
>
>
>
>
>
> --
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> <http://r-sig-geo.2731867.n2.nabble.com/Problems-with-Kcross-inhom-tp7584914p7584920.html>
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>
> --
> Julia
>
>
>
>
> --
>
> Saludos
>
> David Villalobos Chaves
> Maestría Académica en Biología
> Universidad de Costa Rica
>
>
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