Mathematics |

**Example: Solving a Fully Implicit ODE Problem**

The following example shows how to use the function `ode15i`

to solve the implicit ODE problem defined by Weissinger's equation

with the initial value . The exact solution of the ODE is

The example uses the function `weissinger`

, which is provided with MATLAB, to compute the left-hand side of the equation.

Before calling `ode15i`

, the example uses a helper function `decic`

to compute a consistent initial value for . In the following call, the given initial value is held fixed and a guess of 0 is specified for . See the reference page for `decic`

for more information.

You can now call `ode15i`

to solve the ODE and then plot the numerical solution against the analytical solution with the following commands.

Solver for Fully Implicit ODEs | Changing ODE Integration Properties |

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