# [R] envelopes of simulations

Mon Jan 16 05:04:13 CET 2006

```Sara Mouro writes:
> Hello!
>
> I am writing you because I could not plot the confidence envelopes for
> functions Jest, Jcross, Jdot, Jmulti, and L, using the Spatstat package.

Enquiries about a package should be sent to the package maintainer
rather than R-help.

> I have already understood how to do that for Kest or Jest, that is:
> JEnv <- plot(envelope(PPPData, Jest))
> 	Where PPPData is my ppp object.
>
> However, for Jcross I must specify the two marks I want to analyse.
> That is, usually I would get the Jcross doing:
> Jc <- Jcross(PPPData,"Aun","Qsu")
> 	For marks "Aun" and "Qsu".

To do this, type
envelope(PPPData, Jcross, i="Aun", j="Qsu")

Explanation:
Looking at help(Jcross) we see that its formal syntax is
Jcross(X, i, j).
This means that when you call
Jcross(PPPData,"Aun","Qsu")
the arguments are matched as
Jcross(X=PPPData,i="Aun",j="Qsu").

So our problem is, how to pass the arguments 	i="Aun" and j="Qsu"
to the function Jcross each time it is called by `envelope'.

The help entry for 'envelope' mentions that `envelope' will accept
extra arguments "..." which are then passed to the function 'fun'.

So, to pass the two argument values i="Aun" and j="Qsu",
just type
envelope(PPPData, Jcross, i="Aun", j="Qsu")

> For L function, I can make:
> K <- Kest (PPPData, correction="isotropic")
> plot (K, r-sqrt(iso/pi)~r)

You can compute the envelope for the K-function
and transform it afterwards.

To plot envelopes of the L function discrepancy
LD(r) = sqrt(K(r)/pi) - r,
just type
E <- envelope(PPPData, Kest, correction="isotropic")
plot(E, sqrt(./pi) -r ~ r)

Hope this helps.
regards