Question

I cannot seem to find how the search distance “r” is calculated in the R Kest function (spatstat). The package documentation states the following:

r Optional. Vector of values for the argument r at which K(r) should
be evaluated. Users are advised not to specify this argument; there is
a sensible default.

What is the “sensible default” used in the calculation? Any documentation would be greatly appreciated.

Answer 1

Because R is open source you can read the code yourself. Typing Kest lists the code. Finding where r is assigned shows it is done by a subroutine called handle.r.b.args. Type its name at the R prompt to read the procedure–it’s only a half dozen lines:

    rmax <- if (missing(rmaxdefault)) 
        diameter(as.rectangle(window))
    else rmaxdefault
    if (is.null(eps)) {
        if (!is.null(window$xstep)) 
            eps <- window$xstep/4
        else eps <- rmax/512
    }
    breaks <- make.even.breaks(rmax, bstep = eps)

Evidently an estimate of the diameter of the region is divided by 512.