ABSTRACT
This chapter focuses on Iterative Proportional Fitting procedure (IPF), a simple, fast and widely-used method to allocate individuals to zones. It then describes the process underlying the method of population synthesis before implementing the IPF algorithm in base R. The chapter also introduces the important concepts of integerisation and expansion. A wide range of methods can be used to allocate individuals to zones in spatial microsimulation. As with the majority of procedures for statistical analysis, there are deterministic and stochastic methods. Integerisation, expansion and compression procedures allow fractional weighting and combinatorial optimisation approaches for population synthesis to be seen as essentially the same thing. The concept of weights is critical to understanding how population synthesis generates spatial microdata. The most widely used and mature deterministic method to allocate individuals to zones is IPF. IPF is mature, fast and has a long history: it was demonstrated by W. Deming and F. F. Stephan for estimating internal cells based on known marginals.
