`isLowIndexDAE`

Tests whether a DAE system has differential index 0 or 1.

Category: Mathematics > Equation Solving

Syntax

tf = isLowIndexDAE(eqs, vars)

Returns true if the system is of low index and can be solved numerically as is.

Description

Numerical DAE solvers such as ode15s and ode15i cope with index 0 or 1, but not with higher indices. A false result means the system must first be reduced, for instance with reduceDAEIndex, before it is converted with daeFunction or massMatrixForm.

Input arguments

eqs: Vector of symbolic equations.
vars: Vector of the unknown symbolic functions.

Output arguments

tf: Logical scalar.

Example

A semi-explicit system of index 1

syms x(t) y(t)
eqs = [diff(x,t) == y, x + y == 1];
isLowIndexDAE(eqs, [x y])

Output

ans = logical
   1

Notes

reduceDAEIndex is not yet implemented in MatLivre.

isLowIndexDAE