plotting issue in MATLAB

plot(r(i),z(n+1), '-b'); does not plot any points but plot(r(i),z(n+1), '.b'); does. I cannot figure it out why. Can anyone here help me regarding this?

Answer 1

[Walter Roberson]

plot() by default does not draw any markers.

plot() only creates lines when there are two or more adjacent finite points.

plot(r(i),z(n+1), '-b');

cannot create a line because it only has a single point. Or you could think of it as producing a line of size zero. And it doesn't create a marker because you did not ask for a marker.

plot(r(i),z(n+1), '.b'); 

asks for a marker (but not for a line). When you specify a marker then by default lines are turned off. If you wanted both you need to ask for both, such as

plot(r, z, '-.b')

Much of the time you should avoid plotting each point as it is calculated, and instead store the values and plot() after the end of the loop.

[Santanu]

Thank you for your comments. Actually this runs under a loop parametrized by i and n with "hold on" and "hold off'. Even using "plot(r, z, '-.b')" does not work. Any help would be appreciated.

[Voss]

plot(r, z, '.-b')

[Santanu]

Thank you @Voss. It worked by changing that a bit(keeping it out of the loop).