Why do I receive an error saying "Plots must be of the same type and size to be superimposed" when running the uss.step function from Robust Control Toolbox 3.4 (R2009b)?

I am currently running sample code from the Robust Control Toolbox.

At the line:

step(G,2)

I receive the following error: ERROR: Plots must be of the same type and size to be superimposed

Answer 1

[MathWorks Support Team]

This error typically occurs when the following conditions are true:

1) The current axes (gca) contain a plot of different nature (e.g., BODE)

2) HOLD ON was applied to these axes

The error occurs because a BODE plot and a STEP plot cannot be superimposed (which is what HOLD ON requests).

In order to work around this issue, either toggle the HOLD on the current axes, or open a new figure window.