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Specify species and parameter interactions


The Rule property contains a rule that defines how certain species and parameters should interact with one another. For example, a rule could state that the total number of species A and species B must be some value. Rule is a MATLAB® expression that defines the change in the species object quantity or a parameter object Value when the rule is evaluated.

You can add a rule to a model object with the addrule method and remove the rule with delete. For more information on rules, see addrule and RuleType.


If you set the Rule property for an algebraic rule, rate rule, or repeated assignment rule, and the rule expression is not continuous and differentiable, see Using Events to Address Discontinuities in Rule and Reaction Rate Expressions before simulating your model.


Applies toObject: rule
Data typeCharacter vector
Data valuesCharacter vector defined as species or parameter objects. Default is an empty character vector ''.


  1. Create a model object, and then add a reaction object.

    modelObj = sbiomodel ('my_model');
    reactionObj = addreaction (modelObj, 'a + b -> c + d');
  2. Add a rule.

    ruleObj = addrule(modelObj, '10-a+b')

    MATLAB returns:

    SimBiology Rule Array
    Index:    RuleType:    Rule:
    1         algebraic    10-a+b