MATLAB Mathematics - SERC - Index of

5 Differential Equations
1
Robertson DAE problem with a Conservation Law, solved by ODE15S
0.9
0.8
0.7
0.6
1e4 * y(:,2)
0.5
0.4
0.3
0.2
0.1
0
10 −6 10 −4 10 −2 10 0 10 2 10 4 10 6 10 8
This is equivalent to the stiff ODEs coded in HB1ODE.
Example: Computing Nonnegative Solutions
If certain components of the solution must be nonnegative, use odeset to set
the NonNegative property for the indices of these components.
Note This option is not available for ode23s, ode15i, and for implicit solvers
(ode15s, ode23t, ode23tb) applied to problems where there is a mass matrix.
Imposing nonnegativity is not always a trivial task. We suggest that you use
this option only when necessary, for example in instances in which the
application of a solution or integration will fail otherwise.
Consider the following initial value problem solved on the interval [0, 40]:
y' = - |y|, y(0) = 1
The solution of this problem decays to zero. If a solver produces a negative
approximate solution, it begins to track the solution of the ODE through this
value, the solution goes off to minus infinity, and the computation fails. Using
the NonNegative property prevents this from happening.
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