While debugging some code I noticed thatexamples/pvtol-nested.py was producing a blank figure instead of a pole-zero map that was expected. I chased this down tto the fact that thesgrid() function callsmatplotlib.pyplot.figure(). This is in contrast to all other plotting routines and the consequence is that you get a new set of axes. This causes the following code (fromexamples/pvtol-nested.py) not to work as expected:

figure(10); clf();(P, Z) = pzmap(T, Plot=True)print("Closed loop poles and zeros: ", P, Z)# Gang of Fourfigure(11); clf();gangof4(Hi*Po, Co);

Figure 10, which should have the output ofpzmap will be blank sincepzmap callsfigure() (throughsgrid) and creates a new set of axis (figure#11). Figure#11 will then get erased (away goes the pole/zero map) and be replace by the Gang of 4.