Isotropic edge correction unbiasedness
Hi Adrian, One followup I can't find answered in the book -- is there an analogue to the isotropic edge correction in kest.fft? Or does it only do border? Thanks! Nick
On Wed, Jul 27, 2016 at 10:58 AM Nick Eubank <nickeubank at gmail.com> wrote:
Great, thanks so much for taking the time to answer this Adrian! And for the book link! On Wed, Jul 27, 2016 at 3:25 AM Adrian Baddeley < adrian.baddeley at curtin.edu.au> wrote:
Nick Eubank writes:
Using `kest` to estimate a ripley's K for a country.
This is a question about the 'spatstat' package. The function name is 'Kest'.
The authors of the package suggest isotropic is best when
computationally tractable for
irregular shapes, but I noticed in Ripley (1988) that this correction is only "unbiased provided E is convex", where E is the boundaries of
study. This is covered at length in Chapter 7 of the 'spatstat book' < https://www.crcpress.com/Spatial-Point-Patterns-Methodology-and-Applications-with-R/Baddeley-Rubak-Turner/p/book/9781482210200 The isotropic corrected estimate is unbiased for all r < R, where R is the radius of the smallest circle that encloses the entire window (assuming the window is connected).
With that said, the picture in Ripley (1988) illustrating this
correction
is NOT convex (it's a kidney shape).
So the statement above applies to this window.
I know this isn't quite an "r-implementation" question, but: anyone
know if
isotropic correction is unbiased for an odd shape like a country-outline (in this case Sweden)? Or should i use the `border` correction?
Use the isotropic correction. Adrian Baddeley