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The LinearInteraction component allows to model the interaction between two stocks A (portA
) and B (portB
) as linear equations:
Note: Capital letters were chosen to represent the stocks (state variables) connected at portA
and portB
in the formula above. Also dot notation is used for a stock's rate of flow—its first derivative with respect to time.
Coefficient | Unit | Description |
---|---|---|
a_0 |
base units for flow to A ( |
Rate of growth for stock A |
|
base units for flow to B ( |
Rate of growth for stock B |
|
1/s |
Fractional rate of growth for stock A |
|
1/s |
Fractional rate of growth for stock B |
|
base units for flow to A ( |
Rate of growth for stock A per stock B |
|
base units for flow to B ( |
Rate of growth for stock B per stock A |
The coefficients can be given as parameters or as variables via the expandable connector dataIn
.
A linear harmonic oscillator can be modeled as a special case of linear interactions where the rates for the mutual influences (e.g., fractionalGrowthRate_B_per_A and fractionalGrowthRate_A_per_B) are negative. In that case, positive stock A will decrease stock B and vice versa.
The Linear Interaction can be used to model Strogatz' famous model for the dynamics of a love affair (conspicuously between "Romeo" and "Juliet") as shown in →LoveHateDynamics [16].
OutputType_A
and OutputType_B
will be used to conveniently set the types, e.g., units, of the parameters a_0,a_B
and b_0, b_A
.a_B
might have rather convoluted units, e.g., base units of A/(base units of B.s)
. For convenient modeling, a_B
will be divided by refB
, which allows to use displayUnit
should unit conversion be required. Since TypeB
by default is set to Unspecified
in most cases nothing needs to be done.b_A
.NonlinearInteraction, ComplexInteraction
Name | Description |
---|---|
TypeA | Type selector for stock A (default = Unspecified) |
TypeB | Type selector for stock B (default = Unspecified) |
Input_Connector | Data bus for inputs |
Input_Connector
defined as encapsulated expandable connector
in v2.1.0.unspecified
in v2.1.0.