[R] Random labeling hypothesis in spatstat
Karla Falk
karlafalk at trentu.ca
Fri Feb 20 21:27:55 CET 2009
Hi,
I am trying to test the random labeling hypothesis with my data. I have a point pattern of bird nests and each nest has a mark that it is either predated or not-predated. I want to test the null hypothesis that the K distribution of predation events is equal to the K distribution of all events (nests). This is the code I am using:
Kdif <- function(X,...,i) {
Kidot <- Kdot(X,...,i=i)
K <- Kest(X,...)
dif <- eval.fv(Kidot-K)
return(dif)
}
E <- envelope(ppp, Kdif, nsim=100, i="Predated", simulate=expression(rlabel(ppp)))
plot(E, main="clustering of predation events")
I got this code from the 'Analazing spatial patterns in R Workshop notes', and it works fine, but not sure I understand exactly what it means. Specifically I want to make sure that the Kidot is just looking at the distribution of predation events, but I am not sure if it is doing this. What does Kdot(X,...,i=i) mean exactly? It is much appreciated if anyone can help me understand this. Thank you. Karla
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