Unit composition


The Composition property holds the composition of a unit object. The Composition property shows the combination of base and derived units that defines the unit. For example, molarity is the name of the unit and the composition is mole/liter. Base units are the set of units used to define all unit quantity equations. Derived units are defined using base units or mixtures of base and derived units.

Valid physical quantities for reaction rates are amount/time, mass/time, or concentration/time.


Applies toObject: Unit
Data typeCharacter vector
Data values

Valid combination of units and prefixes from the library. Default is '' (empty).



This example shows you how to create a user-defined unit, add it to the user-defined library, and query the Composition property.

  1. Create a unit for the rate constants of a second-order reaction.

    unitObj = sbiounit('secondconstant', '1/molarity*second', 1); 
  2. Query the Composition property.

    get(unitObj, 'Composition')
    ans =
  3. Change the Composition property.

    set(unitObj, 'Composition', 'liter/mole*second'))
    ans =
  4. Add the unit to the user-defined library.