Two Independent Variables

Abstract

This chapter discusses how to handle two independent variables in a STELLA II model Time is our usual independent variable and we use it to cause the change in our models. First we introduce several stock variables to indicate various temporal aspects of the state variable of the system. Such a disaggregation can be done, for example, for a population into different age classes. Here we deal only with a more sophisticated representation of essentially a single variable—population. In the following section we use the same modeling method to disaggregate a system not only with respect to the temporal dimension of the system but also with respect to its spatial dimension. By doing so, we model two independent variables—space and time. First, however, let’s disaggregate the state variable with respect to the temporal dimension.