odeset (MATLAB Function Reference)

Create or alter options structure for input to ODE solvers

options = odeset('name1',value1,'name2',value2,...)
options = odeset(oldopts,'name1',value1,...)
options = odeset(oldopts,newopts)
odeset

Description

The odeset function lets you adjust the integration parameters of the ODE solvers. See below for information about the integration parameters.

options = odeset('name1',value1,'name2',value2...)

creates an integrator options structure in which the named properties have the specified values. The odeset function sets any unspecified properties to the empty matrix [].

It is sufficient to type only the leading characters that uniquely identify the property name. Case is ignored for property names.

options = odeset(oldopts,'name1',value1,...)

alters an existing options structure with the values supplied.

options = odeset(oldopts,newopts)

alters an existing options structure oldopts by combining it with a new options structure newopts. Any new options not equal to the empty matrix overwrite corresponding options in oldopts. For example:

odeset

by itself, displays all property names and their possible values:

odeset
      AbsTol: [ positive scalar or vector {1e-6}]
      BDF: [ on | {off} ]
      Events: [ on | {off} ]
      InitialStep: [ positive scalar ]
      Jacobian: [ on | {off} ]
      JConstant: [ on | {off} ]
      JPattern: [ on | {off} ]
       Mass: [ on | {off} ]
       MassConstant: [ on | {off}] 
      MaxOrder: [ 1 | 2 | 3 | 4 | {5} ]
       MaxStep: [ positive scalar ]
      OutputFcn: [ string ]
      OutputSel: [ vector of integers ]
      Refine: [ positive integer ]
      RelTol: [ positive scalar {1e-3} ]
      Stats: [ on | {off} ]
      Vectorized: [ on | {off} ]

Properties

The available properties depend upon the ODE solver used. There are seven principal categories of properties:

Error tolerance
Solver output
Jacobian
Event location
Mass matrix
Step size
ode15s

**Table 2-1: Error Tolerance Properties**
Property	Value	Description
`RelTol`	Positive scalar {`1e-3`}	A relative error tolerance that applies to all components of the solution vector.
`AbsTol`	Positive scalar or vector {`1e-6`}	The absolute error tolerance. If scalar, the tolerance applies to all components of the solution vector. Otherwise the tolerances apply to corresponding components.

**Table 2-2: Solver Output Properties**
Property	Value	Description
`OutputFcn`	String	The name of an installable output function (for example, `odeplot`, `odephas2`, `odephas3`, and `odeprint`). The ODE solvers call `outputfcn(TSPAN,Y0,'init')` before beginning the integration, to initialize the output function. Subsequently, the solver calls `status = outputfcn(T,Y)` after computing each output point `(T,Y)`. The `status` return value should be `1` if integration should be halted (e.g., a STOP button has been pressed) and 0 otherwise. When the integration is complete, the solver calls `outputfcn([],[],'done')`.
`OutputSel`	Vector of indices	Specifies which components of the solution vector are to be passed to the output function.
`Refine`	Positive Integer	Produces smoother output, increasing the number of output points by a factor of `n`. In most solvers, the default value is `1`. However, within `ode45`, `Refine` is `4` by default to compensate for the solver's large step sizes. To override this and see only the time steps chosen by `ode45`, set `Refine` to `1`.
`Stats`	on \| {off}	Specifies whether statistics about the computational cost of the integration should be displayed.

**Table 2-3: Jacobian Matrix Properties (for ode15s and ode23s)**
Property	Value	Description
`JConstant`	on \| {off}	Specifies whether the Jacobian matrix is constant (see `b5ode`).
`Jacobian`	on \| {off}	Informs the solver that the ODE file responds to the arguments (`t,y,'jacobian'`) by returning (see `odefile`).
`JPattern`	on \| {off}	Informs the solver that the ODE file responds to the arguments (`[],[],'jpattern'`) by returning a sparse matrix containing `1`'s showing the nonzeros of (see `brussode`).
`Vectorized`	on \| {off}	Informs the solver that the ODE file `F(t,y)` has been vectorized so that `F(t,[y1 y2 ...])` returns `[F(t,y1) F(t,y2) ...]`. That is, your ODE file can pass to the solver a whole array of column vectors at once. Your ODE file will be called by a stiff solver in a vectorized manner only if generating Jacobians numerically (the default behavior) and `odeset` has been used to set `Vectorized` to `'on'`.

**Table 2-4: Event Location Property**
Property	Value	Description
`Events`	on \| {off}	Instructs the solver to locate events. The ODE file must respond to the arguments (`t,y,'events'`) by returning the appropriate values. See `odefile`.

**Table 2-5: Mass Matrix Properties (for ode15s and ode23s)**
Property	Value	Description
`Mass`	on \| {off}	Informs the solver that the ODE file is coded so that `F(t,[],'mass')` returns or (see `odefile`).
`MassConstant`	on \| {off}	Informs the solver that the ODE file is coded so that `F(t,[],'mass')` returns a constant mass matrix (see `odefile`).

**Table 2-6: Step Size Properties**
Property	Value	Description
`MaxStep`	Positive scalar	An upper bound on the magnitude of the step size that the solver uses.
`InitialStep`	Positive scalar	Suggested initial step size. The solver tries this first, but if too large an error results, the solver uses a smaller step size.

In addition there are two options that apply only to the ode15s solver.

**Table 2-7: ode15s Properties**
Property	Value	Description
`MaxOrder`	1 \| 2 \| 3 \| 4 \| {5}	The maximum order formula used.
`BDF`	on \| {off}	Specifies whether the Backward Differentiation Formulas (BDF's) are to be used instead of the default Numerical Differentiation Formulas (NDF's).