`odephas2`

ODE output function: 2-D phase plane plot, drawn while the solver runs.

Category: Other public functions: funfun

Syntax

status = odephas2(t, y, flag)

Output-function form: called by the solver at the start, at each accepted step and at the end.

Description

Pass @odephas2 as the 'OutputFcn' option of odeset and the solver calls it at every step. It draws the first state component against the second, which shows the trajectory of a two-variable system, such as an oscillator, as a curve in the phase plane. The solver, not the user, normally invokes it.

For three states use odephas3. To plot every component against time use odeplot.

Input arguments

t, y: Time points and state columns passed in by the solver.
flag: 'init', '' or 'done', telling which phase the solver is in.

Output arguments

status: Logical, true to ask the solver to stop. The plotting functions always return false.

Example

Phase portrait of an oscillator

opts = odeset('OutputFcn', @odephas2);
[t, y] = ode45(@(t, y) [y(2); -y(1)], [0 10], [1; 0], opts);

In the app, the phase-plane curve (a circle) is drawn below the code.

odephas2