信封函数（spatstat）-错误“未使用的参数”

Question

I would like to ask your help for finding the reason why when I use the function envelope, my arguments are not accepted, but defined "unused arguments". The data I'm using are ppp without marks and I would like to create a L function graph with simulated data and my data. Here the code for my ppp data:

 map2008MLW = ppp(xy2008_BNGppp$x, xy2008_BNGppp$y, window = IoM_polygon_MLWowin)

And then:

L2008 = Lest(map2008MLW,correction="Ripley")
OP = par(mar=c(5,5,4,4))
plot(L2008, . -r ~ r, ylab=expression(hat("L")), xlab = "d (m)"); par(OP)
L2008$iso  = L$iso  - L$r
L2008$theo = L$theo - L$r

Desired number of simulations

n = 9999

Desired p significance level to display

 p  = 0.05

And at this point the envelope function doesnt seem very happy:

    EL2008 = envelope(map2008MLW[W], Lest, nsim=n, rank=(p * (n + 1)))
    Error in envelope(map2008MLW[W], Lest, nsim = n, rank = (p * (n + 1))) : 
  unused arguments (nsim = n, rank = (p * (n + 1)))

It seems a generic error and I am not sure it is caused by the package spatstat. Please, help me in finding a solution to this, as I can't proceed with my analyses.

Thank you very much,

Martina

Answer 1

The argument rank should be nrank .

Also the relationship between the significance level and the argument nrank is not correct in the example. For a two-sided test, the significance level is alpha = 2 * nrank/(nsim+1) , so nrank= alpha * (nsim+1)/2 .

You have chosen a significance level of 0.95 but I assume you mean 0.05 . So with nsim=9999 you want nrank=0.05 * 10000/2 = 250 to get a test with significance level 0.05.

Such a large number of simulations (9999) is unnecessary in this kind of application. Monte Carlo tests are valid with small values of nsim . In your example I would normally use nsim=39 and nrank=1 .

See Chapter 10 of the spatstat book .