Journal of Control Engineering and Applied Informatics
Using A Quick-Basic Application Based On The DAC Statistic To Detect Spatial Clusters
Abstract
Spatial distributions find applications in various fields, such as public health, biology,
ecology, geography, economics or sociology. The DAC statistic is the difference between the
empirical cumulative distribution of cases and that of non-cases at a particular point. This study
uses the longitude and latitude as the coordinates of the homes of mothers in Spartanburg County,
SC who gave birth to their babies in 1989 or 1990. A priori, clusters are expected in areas of high
population densities, especially considering risk factors for low birthweight. The chosen axes are
east-west (x) and north-south (y). From a mathematical perspective the choice is arbitrary. For
any size of a random sample of locations taken from the 6434 live births there is a noticeable
variation of the location of the DAC statistic with random rotations within a given sample, when
transformed back to original longitude and latitude. Simulations indicated that the location of the
maximum DAC statistic is not unique, moreover there is a geometrical locus of it, and this varies
as the orientation of the axes changes. Therefore, the DAC statistic should be used with caution,
but its usefulness as a set of spatial descriptive statistic is not diminished in the least.
ecology, geography, economics or sociology. The DAC statistic is the difference between the
empirical cumulative distribution of cases and that of non-cases at a particular point. This study
uses the longitude and latitude as the coordinates of the homes of mothers in Spartanburg County,
SC who gave birth to their babies in 1989 or 1990. A priori, clusters are expected in areas of high
population densities, especially considering risk factors for low birthweight. The chosen axes are
east-west (x) and north-south (y). From a mathematical perspective the choice is arbitrary. For
any size of a random sample of locations taken from the 6434 live births there is a noticeable
variation of the location of the DAC statistic with random rotations within a given sample, when
transformed back to original longitude and latitude. Simulations indicated that the location of the
maximum DAC statistic is not unique, moreover there is a geometrical locus of it, and this varies
as the orientation of the axes changes. Therefore, the DAC statistic should be used with caution,
but its usefulness as a set of spatial descriptive statistic is not diminished in the least.