massMatrixForm

Writes a DAE system in mass-matrix form M*y' = F(t, y).

Category: Mathematics > Equation Solving

Syntax

[M, F] = massMatrixForm(eqs, vars)

Description

Many solvers (ode15s, ode23t) accept problems as M(t,y) y' = f(t,y). massMatrixForm extracts that structure from the equations. It works only if the system is linear in the derivatives, and the result can feed odeFunction and the Mass option of odeset.

Input arguments

eqs

Vector of symbolic equations.

vars

Vector of unknown symbolic functions, in the order of the columns of M.

Output arguments

M

Symbolic mass matrix. Rows of zeros mark algebraic equations.

F

Column vector of expressions in t and the variables.

Example

One differential and one algebraic equation

syms x(t) y(t)
eqs = [diff(x,t) == y, x + y == 1];
[M, F] = massMatrixForm(eqs, [x y])

M = 
[1, 0]
[0, 0]
F = 
           y(t)
1 - x(t) - y(t)

See also

daeFunction odeFunction isLowIndexDAE odeset