How to make a root locus plot square aspect ratio

I have tried:

s = tf('s');

sysL = (s^2+1)/(s*(s^2+4));

rlocus(sysL);

v=[-4 4 -4 4];
axis(v);
axis('square');

But I get a message that says: Warning: This plot type does not support this option for the "axis" command.

I am using 2013b

Answer 1

[Star Strider]

It does not support axis('square'). It does support axis('equal'), but that overrides your axis(v) call.

You can override the aspect ratio with the 'Position' figure property:

s = tf('s');
sysL = (s^2+1)/(s*(s^2+4));
rlocus(sysL);
v=[-4 4 -4 4]; axis(v);
hpos = get(gcf, 'Position');                    % Get 'Position'
set(gcf, 'Position',[hpos([1 2 4]) hpos(4)])    % Set Width = Height

Experiment to get the result you want.

[Daniel]

OK. That is better than what I started with.

However, is there any way to force a square aspect ratio? I don't really need the axis(v) since I did that just to try to force an equal axis length which axis('equal') already accomplishes.

My problem is that if the plot doesn't come up as a square or if I manually resize the plot, then the angles look all messed up.

[Daniel]

Great. I modified your code a bit to re-capture what axis('equal') does, since I like that function and it saves me the step of trying to figure out what my axis limits should be.

s = tf('s');
sysL = (s^2+1)/(s*(s^2+4));
rlocus(sysL);
hpos = get(gcf, 'Position');                    % Get 'Position'
set(gcf, 'Position',[hpos([1 2 4]) hpos(4)])    % Set Width = Height
axis('equal');

[Ryszard Nowacki]

Is there any way to do this with the R2023b version?

[Star Strider]

@Ryszard Nowacki — I just now tested that same code here (R2023b), and it seems to work correctly.

Comparing them —

s = tf('s');
sysL = (s^2+1)/(s*(s^2+4));

figure
rlocus(sysL);

figure
rlocus(sysL);
hpos = get(gcf, 'Position');                    % Get 'Position'
set(gcf, 'Position',[hpos([1 2 4]) hpos(4)])    % Set Width = Height
axis('equal');

It works as desired in R2023b.

.