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The Joins Count
Extreme Negative AC
Provides a metric for the correlation among areal units.
Each aeral unit is classified as either black (B) or white (W)
The joins count is determined by counting the number of occurrences in the map of each of the possible joins [BB, WW, BW]
Extreme Positive AC
No AC
Moran’s I
jiij
n
ii
n
i
n
jjiij
wyy
yyyywn
I
1
2
1 1
Moran’s I typically ranges for -1 to 1. An uncorrelated process has an expected I=0. Negative values of I indicate negative autocorrelation. Positive values indicate positive autocorrelation
2000 Presidential Election Results
Adjacency Matrix
149.710
jiij
n
ii
n
i
n
jjiij
wyy
yyyywn
I
1
2
1 1
354.95071 1
n
i
n
jjiij yyyyw
218
jiijw
49n
531.52061
2
n
ii yy
Moran’s I of 0.4 indicates a fairly strong postive correlation between Bush votes in neighboring states
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Air Pollution Trajectory Analysis
Residence Time is the amount of time an air mass has spent in a grid cell on it’s way to a particular location.
Res. Times All ConditionsRes. Times High Pollutants
ΣRes. Times High( Σ All Res. Times(( (Incremental Residence Time Probability =