Strange result with a constant in Vensim
Posted: Fri Nov 30, 2018 10:43 pm
I'm developing a model that I can't share publicly at this stage, but it's giving seemingly-strange results (probably PEBKAC, but I don't see it yet).
I defined a subscripted variable (Dmnl) called Light Extinction Ratio and defined it as a Normal Constant with value 0.1 (as a placeholder) for each of its five subscript values. That is, there are five equations, because this variable might eventually have different values for different subscripts.
Ctrl-t says the model is good.
I can run the model and then look the results using the Table tool:
Has anyone ever seen something like this? Better yet, does anyone have an idea why it's happening or what I should look for?
In case it helps, here are the first few lines of the model, which include the definition of this variable:
I'm running DSS 7.3.4.
I defined a subscripted variable (Dmnl) called Light Extinction Ratio and defined it as a Normal Constant with value 0.1 (as a placeholder) for each of its five subscript values. That is, there are five equations, because this variable might eventually have different values for different subscripts.
Ctrl-t says the model is good.
I can run the model and then look the results using the Table tool:
- Light Extinction Ratio(1) is 24.9599 for every time step.
Light Extinction Ratio(2-4) is 1e-06 for every time step.
Has anyone ever seen something like this? Better yet, does anyone have an idea why it's happening or what I should look for?
In case it helps, here are the first few lines of the model, which include the definition of this variable:
Code: Select all
{UTF-8}
:MACRO:
TEMP2HEAT(temperature,specificheath2o,literspercufooth2o,densityh2o)
TEMP2HEAT = (temperature+273)*densityh2o*specificheath2o*literspercufooth2o
~ kJ/(ft*ft*ft)
~ The heat in water per ft^3 at a specific temperature in deg. C.
|
:END OF MACRO:
:MACRO:
HEAT2TEMP(heat,water,specificheath2o,literspercufooth2o,densityh2o)
HEAT2TEMP = heat / (water * specificheath2o * densityh2o * literspercufooth2o) - 273
~ C
~ Heat contained in a stock or flow of water
|
:END OF MACRO:
Light Extinction Ratio["Reach 3.1"]=
0.1 ~~|
Light Extinction Ratio["Reach 3.2"]=
0.1 ~~|
Light Extinction Ratio["Reach 3.3"]=
0.1 ~~|
Light Extinction Ratio["Reach 3.4"]=
0.1 ~~|
Light Extinction Ratio["Reach 3.5"]=
0.1
~ Dmnl
~ |