3.1 Local Moran
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The Local Moran statistic was suggested in Anselin () as a way to identify local clusters and local spatial outliers. For more details, please read
Short version:
Full version:
Name
Type
Description
val
numeric
the numeric column that contains the values for LISA statistics
weights
bytea
the bytea column that stores the spatial weights information
permutations
integer
the number of permutations for the LISA computation. Default: 999.
permutation_method
character varying
the permutation method used for the LISA computation. Options are 'complete', 'lookup'. Default: 'lookup'.
significance_cutoff
float
the cutoff value for significance p-values to filter not-significant clusters. Default: 0.05.
cpu_threads
integer
the number of cpu threads used for parallel LISA computation. Default: 6.
seed
integer
the seed for random number generator used in LISA statistics. Default: 123456789.
Type
Description
float[]
an array contains 3 values, which are {'lisa value', 'pseudo-p value' and 'cluster indicator'}
One can specify the arguments of local moran using the full version of local_moran() function. For example, apply local moran statistics using 9,999 permutations, significance cutoff value 0.01:
The predefined values of the cluster indicators of local moran are:
Cluster indicator value
Description
Color
0
Not significant
#eeeeee
1
High-High
#ff0000
2
Low-Low
#0000ff
3
Low-High
#a7adf9
4
High-Low
#f4ada8
5
Undefined Value
#464646
6
Isolated
#999999
One can extract the cluster indicators and make a local moran cluster map using the 'Color" values in the table above:
Or by extracting the pseudo-p values to make a significance map:
Apply local moran statistics on the variable "hr60" (homicide rate 1960 in ) using queen contiguity weights "queen_w":
Please see chapter '' for how to create a Queen contiguity weights.