Simbiology: using a dummy species to fit data to a sum of real species with sbiofit

Hello,

Let's say I have a model with two species:

addspecies('compartment1',s1,'InitialAmount',100,'InitialAmountUnits','nanomole')
addspecies('compartment1',s2,'InitialAmount',50,'InitialAmountUnits','nanomole')

and now I am trying to fit a trace 'DATA' to the sum of these two species using sbiofit. I thought I could simply do this in two steps:

1) add a dummy species to track the sum

addspecies('compartment1',sDummy,'InitialAmount',0,'InitialAmountUnits','nanomole')
addrule(model,'sDummy = compartment1.s1 + compartment1.s2')

2) and then in my sbiofit, do a responseMap as follows to map the sum to my data:

responseMap = {'sDummy = DATA'};

However, I can't even get past step 1. Every time I add my sDummy species to the model and add that rule, it simply zeros out species1 and species2, it's very bizarre.

My questions are:

• Does adding a dummy species work the way I have described above, or is my conception of using addrule to do that wrong to begin with?
• is there a better way altogether to fit my data to a sum of species?

Answer 1

[Arthur Goldsipe]

I think your idea is reasonable. I believe the problem is with the rule you added. As written, addrule adds an initial assignment rule to the model, which is only evaluated at time=0. If you want the rule to be in effect at all times, then you need to create a repeated assignment rule. You can do that by changing the line of code to the following:

addrule(model,'sDummy = compartment1.s1 + compartment1.s2', 'repeatedAssignment');

If that doesn't solve the problem, let us know here.