Hi everyone,
The Spatial Dependence (spdep) library, has a function called
'dnearneigh', which identifies neighbours of region points by Euclidean
distance between lower (greater than) and upper (less than or equal to) bounds.
The function returns a list of integer vectors giving the region id numbers for
neighbours satisfying the distance criteria.
I have used this to identify the euclidean distance of all points falling within
0-2000m of each of my surveys locations. Once distances are converted to
inverse euclidean distances, the list looks something like this:
[[1]]
[1] 15.617376 0.535176 0.569497
[[2]]
[1] 15.6173762 0.5415378 0.5773159
[[3]]
[1] NA
etc.
For each of these points I also have presence/absence data for a particular owl
species (all the location, PA, etc. is kept in a single data frame). Is there a
way of creating a similar list to the one above, identifying the Presence or
Absence of an owl at each of the points that fall with in 0-2000m of the
interested site??
I am attempting to determine the following equation for each site, at a number
of spatial lags, i.e. 0-2000, 0-4000, etc
Autocovariatei = Sum wij yj / Sum wij
Variables: Autocovariate for stop i
yj = Presence (1) or Absence (0) at stop j
wij = the inverse Euclidean distance between
stops i and j
Any help would be greatly appreciated.
Mark
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