ncf (version 1.3-2)

lisa.nc: Non-centered indicators of spatial association

Description

lisa.nc is a function to estimate the (non-centred) multivariate local indicators of spatial association. The function requires multiple observations at each location. For single observations at each location use lisa.

Usage

lisa.nc(
  x,
  y,
  z,
  neigh,
  na.rm = FALSE,
  resamp = 999,
  latlon = FALSE,
  quiet = FALSE
)

Arguments

x

vector of length n representing the x coordinates (or latitude; see latlon).

y

vector of length n representing the y coordinates (or longitude).

z

a matrix of dimension n x p representing p (>1) observation at each location.

neigh

neighborhood size.

na.rm

If TRUE, NA's will be dealt with through pairwise deletion of missing values.

resamp

number of resamples under the NULL to generate p-values

latlon

If TRUE, coordinates are latitude and longitude.

quiet

If TRUE, the counter is suppressed during execution.

Value

An object of class "lisa" is returned, consisting of the following components:

correlation

the mean correlation within the neighborhood (neigh).

p

the permutation two-sided p-value for each distance-class.

n

the number of pairs within each neighborhood.

dmean

the actual mean of distance within each neighborhood.

coord

a list with the x and y coordinates.

Details

This is the function to estimate the (non-centered) local indicators of spatial association modified form Anselin (1995). 'correlation' is the average correlation within a neighborhood. The function requires multiple observations at each location.

Missing values are allowed -- values are assumed missing at random, and pairwise complete observations will be used.

References

Anselin, L. 1995. Local indicators of spatial association - LISA. Geographical Analysis 27:93-115. <doi:10.1111/j.1538-4632.1995.tb00338.x>

See Also

lisa

Examples

# NOT RUN {
# first generate some sample data
x <- expand.grid(1:20, 1:5)[, 1]
y <- expand.grid(1:20, 1:5)[,2]

# z data from an exponential random field
z <- cbind(
  rmvn.spa(x = x, y = y, p = 2, method = "exp"), 
  rmvn.spa(x = x, y = y, p = 2, method = "exp")
  )

# lisa.nc analysis
fit1 <- lisa.nc(x = x, y = y, z = z, neigh = 3)
# }
# NOT RUN {
plot(fit1)
# }