Analysis of Binary Multivariate Longitudinal Data via 2-Dimensional Orbits: An Application to the Agincourt Health and Socio-Demographic Surveillance System in South Africa.
We analyse demographic longitudinal survey data of South African (SA) and Mozambican (MOZ) rural households from the Agincourt Health and Socio-Demographic Surveillance System in South Africa. In particular, we determine whether absolute poverty status (APS) is associated with selected household variables pertaining to socio-economic determination, namely household head age, household size, cumulative death, adults to minor ratio, and influx. For comparative purposes, households are classified according to household head nationality (SA or MOZ) and APS (rich or poor). The longitudinal data of each of the four subpopulations (SA rich, SA poor, MOZ rich, and MOZ poor) is a five-dimensional space defined by binary variables (questions), subjects, and time. We use the orbit method to represent binary multivariate longitudinal data (BMLD) of each household as a two-dimensional orbit and to visualise dynamics and behaviour of the population. At each time step, a point (x, y) from the orbit of a household corresponds to the observation of the household, where x is a binary sequence of responses and y is an ordering of variables. The ordering of variables is dynamically rearranged such that clusters and holes associated to least and frequently changing variables in the state space respectively, are exposed. Analysis of orbits reveals information of change at both individual- and population-level, change patterns in the data, capacity of states in the state space, and density of state transitions in the orbits. Analysis of household orbits of the four subpopulations show association between (i) households headed by older adults and rich households, (ii) large household size and poor households, and (iii) households with more minors than adults and poor households. Our results are compared to other methods of BMLD analysis.
Department of Pure and Applied Mathematics, University of Johannesburg, Johannesburg, South Africa.
Maria Vivien
MV
Visaya
School of Computational and Applied Mathematics, University of the Witwatersrand, Johannesburg, South Africa.
David
D
Sherwell
Discipline of Public Health Medicine, School of Nursing and Public Health, University of KwaZulu-Natal, Durban, South Africa.
Benn
B
Sartorius
Graduate School of Informatics, Kyoto University, Kyoto, Japan.
Fabien
F
Cromieres
D003710:Demography; D005191:Family Characteristics; D006801:Humans; D008137:Longitudinal Studies; D015233:Models, Statistical; D009073:Mozambique / Q000453:epidemiology; D011159:Population Surveillance / Q000379:methods*; D011203:Poverty / Q000706:statistics & numerical data*; D012424:Rural Population; D012959:Socioeconomic Factors; D013019:South Africa / Q000453:epidemiology