nnpop
17
the zone. The second zone is the first zone and the connected region that maximizes the scan statis-
tic, subject to the population and distance constraints. This pattern continues until no additional
zones can be added due to population or distance constraints.
Every zone considered must have a total population less than
ubpop * sum(pop) in the study area.
Additionally, the maximum intercentroid distance for the regions within a zone must be no more
than
ubd * the maximum intercentroid distance across all regions.
Value
Returns a list that includes the location id of the zone and the associated test statistic, counts,
expected counts, and population in the zone. If
type = "all", then each of these elements is a list
or vector corresponding to each respective candidate zone.
Author(s)
Joshua French
References
Yao, Z., Tang, J., & Zhan, F. B. (2011). Detection of arbitrarily-shaped clusters using a neighbor-
expanding approach: A case study on murine typhus in South Texas. International journal of health
geographics, 10(1), 1.
Assuncao, R.M., Costa, M.A., Tavares, A. and Neto, S.J.F. (2006). Fast detection of arbitrarily
shaped disease clusters, Statistics in Medicine, 25, 723-742.
Examples
data(nydf)
data(nyw)
coords = as.matrix(nydf[,c("x", "y")])
mlf.zones(coords, cases = floor(nydf$cases), pop = nydf$pop, w = nyw, lonlat = TRUE)
nnpop
Determine nearest neighbors
Description
nnpop determines the nearest neighbors for a set of observations based on the distance matrix ac-
cording to a population upperbound.
Usage
nnpop(d, pop, ubpop)
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nydf
Arguments
d
An n × n square distance matrix containing the intercentroid distance between
the n region centroids.
pop
A vector of length n containing the population values of the n region centroids.
ubpop
A proportion between 0 and 1 containing the upperbound for the proportion of
total population contained collectively among a set of nearest neighbors.
Details
This function determines the nearest neighbors of each centroid based on the intercentroid distance.
The number of nearest neighbors is limited by the sum of the population values among the nearest
neighbors. The set of nearest neighbors can contain no more than
ubpop * sum(pop) members of
the population. The nearest neighbors are ordered from nearest to farthest.
Value
Returns the indexes of the nearest neighbors as a list. For each element of the list, the indexes are
ordered from nearest to farthest from each centroid.
Author(s)
Joshua French
Examples
data(nydf)
d = SpatialTools::dist1(as.matrix(nydf[,c("longitude", "latitude")]))
nnout = nnpop(d, pop = nydf$pop, ubpop = 0.5)
nydf
Leukemia data for 281 regions in New York.
Description
This data set contains 281 observations related to leukeumia cases in an 8 county area of the state
of New York. The data were made available in Waller and Gotway (2005) and details are provided
there. These data are related to a similar data set in Waller et al. (1994). The longitude and latitude
coordinates are taken from the NYleukemia data set in the SpatialEpi package for plotting purposes.
Usage
data(nydf)
nypoly
19
Format
A data frame with 281 rows and 4 columns:
longitude The longitude of the region centroid. These are NOT the original values provided by
Waller and Gotway (2005), but are the right ones for plotting correctly.
latitude The latitude of the region centroid. These are NOT the original values provided by Waller
and Gotway (2005), but are the right ones for plotting correctly.
population The population (1980 census) of the region.
cases The number of leukemia cases between 1978-1982.
x The original ’longitude’ coordinate provided by Waller and Gotway (2005).
y The original ’latitude coordinate provided by Waller and Gotway (2005).
Source
Waller, L.A. and Gotway, C.A. (2005). Applied Spatial Statistics for Public Health Data. Hoboken,
NJ: Wiley.
References
Waller, L.A., Turnbull, B.W., Clark, L.C., and Nasca, P. (1994) "Spatial Pattern Analysis to Detect
Rare Disease Clusters" in Case Studies in Biometry, N. Lange, L. Ryan, L. Billard, D. Brillinger,
L. Conquest, and J. Greenhouse (eds.) New York: John Wiley and Sons.
nypoly
SpatialPolygonsDataFrame for New York leukemia data.
Description
A SpatialPolygonsDataFrame for the New York leukemia data in
nydf. Note that the coordinates
in the polygon have been projected to a different coordinate system (UTM, zone 18), but the order
of the regions/polygons is the same as in
nydf. This data comes from
Usage
data(nypoly)
Format
A SpatialPolygonDataFrame
Source
Bivand, R. S., Pebesma, E. J., Gomez-Rubio, V., and Pebesma, E. J. (2013). Applied Spatial Data
Analysis with R, 2nd edition. New York: Springer.
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plot.scan
nyw
Adjacency matrix for New York leukemia data.
Description
This data set contains a 281 x 281 adjacency matrix for the New York leukemia data in
nydf.
Usage
data(nyw)
Format
A matrix of dimension 281 x 281.
Source
Waller, L.A. and Gotway, C.A. (2005). Applied Spatial Statistics for Public Health Data. Hoboken,
NJ: Wiley.
References
Waller, L.A., Turnbull, B.W., Clark, L.C., and Nasca, P. (1994) "Spatial Pattern Analysis to Detect
Rare Disease Clusters" in Case Studies in Biometry, N. Lange, L. Ryan, L. Billard, D. Brillinger,
L. Conquest, and J. Greenhouse (eds.) New York: John Wiley and Sons.
plot.scan
Plots object of class
scan.
Description
Plots clusters (the centroids of the regions in each cluster) in different colors. The most likely cluster
is plotted with solid red circles by default. Points not in a cluster are black open circles. The other
cluster points are plotted with different symbols and colors.
Usage
## S3 method for class 'scan'
plot(x, ..., ccol = NULL, cpch = NULL, add = FALSE,
usemap = FALSE, mapargs = list())
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