Variables represent values in a calculation, and come in a number of
varieties:
- Constants
- represent an explicit numerical value, and do not
have a name. Their graphical representation shows the actual value of
the constant.
- Parameters
- are named constants. All instances of a given name
represent the same value, as with all other named variables, so
changing the value of one parameter, either through its edit menu, or
through a slider, will affect all the others of that name.
- Flow variables
- have an input port that defines how the value is
to be calculated. Only one flow variable of a given name can have its
input port connected, as they all refer to the same quantity. If no
input ports are connected, then flow variables act just like
parameters.
- Integral variables
- represent the result of integrating its
input over time by means of the differential
equation solver. The integrand is represented by the input to an
integral operator that is attached to the integral variable.
- Stock variables
- are the columns of Godley tables, and represent
the integral over time of the sum of the flow variables making up the
column.
Variables may be converted between types in the variable edit menu,
available from the context menu, subject to certain rules. For example,
a variable whose input is wired anywhere on the canvas cannot be
changed from ``flow''. Stock variables need to be defined in a Godley
table, and so on.
Subsections
Russell Standish
2017-01-05