# daeoptions

set options for dae solver

## Calling Sequence

    daeoptions()

## Description

If it exists in the dae function calling context the variable `%DAEOPTIONS` the dae function use it to sets options.

This daeoptions function interactively displays a command which should be executed to set various options of the dae solver.

The `dae` function checks if this variable exists and in this case it uses it. For using default values you should clear this variable. Note that `daeoptions` does not create this variable. To create it you must execute the command line displayed by `daeoptions`.

The variable `%DAEOPTIONS` is a list with the following elements:

    list(tstop,imode,band,maxstep,stepin,nonneg,isest)

The default value is:

    list([],0,[],[],[],0,0)

The meaning of the elements is described below.

tstop

  a real scalar or an empty matrix, gives the maximum time for which `g` is allowed to be evaluated. An empty matrix means "no limits" imposed for time.

imode

  if it is 0 `dae` returns only the user specified time point values, and if it is 1 `dae` returns its intermediate computed values.

band

  a two components vector which give the definition `[ml,mu]` of band matrix computed by `jac`;

  `r(i - j + ml + mu + 1,j)` = `dg(i)/dy(j)+cj*dg(i)/dydot(j)`. If `jac` returns a full matrix set `band=[]`

maxstep

  a scalar or an empty matrix, the maximum step size, empty matrix means "no limitation".

stepin

  a scalar or an empty matrix, the minimum step size, empty matrix means "not specified".

nonneg

  a scalar, must be set to 0 if the solution is known to be non negative . In the other case it must be set to 1.

isest

  a scalar, must be set to 0 if the given initial condition is compatible: `g(t0,x0,xdot0)=0`, and set to 1 if `xdot0` is just an estimation.

## See Also

- dae