Different behaviour of hold on depending on order

I'm not sure if it is a bug or feature per se, but it was certainly an unexpected behaviour.

Two following figures produce different output

x = 0:0.1:2*pi;
y = sin(x);
z = cos(x);

figure
plot(x, y)
hold on
plot(x, z)

figure
hold on
plot(x, y)
plot(x, z)

The difference is in presence of "border" on right and upper sides of picture.

Could someone explain to me the reason for this differences?

As far as I understand

figure
plot(x, y)

produces a picture with border, and hold on after that doesn't change the fact.

On the other hand

figure

does not create axes, after that

hold on

creates axes for some reason without the border, after that all plots do not change it for some reason.

Is there an actual way to hardcode the border (or the absence of it) in commands? Why does it work the way it works?

Answer 1

[Arthur Roué]

Didn't know you can create axes with hold on command.

This kind of command, such as axis equal, change properties of your graphic object (see documenation of the command to know which one). You can access thoses properties directly with the axe handle.

x = 0:0.1:2*pi;
y = sin(x);
z = cos(x);

% Create figure
hFig = figure();

% Create an axe. The property 'NextPlot' is the one changing from 'replace'
% to 'add' when calling 'hold on' command
hAxe = axes(hFig, ...
    'NextPlot', 'add', ...
    'Box', 'off'); % 'off' without border (your 2nd case) and 'on' with border (your 1st case)

% Plot in the axe
plot(x, y)
plot(x, z)

Answer 2

[Fangjun Jiang]

Good catch! From the document of hold

"If axes do not exist, then the hold command creates them."

Without an existing axes, "hold on" creates an axes the same way as you run "axes".

The answer to this particular instance is that plot() creates an axes with different options than the default axes() command.

[Sergei Shestakov]

I couldn't believe for a minute that "hold on" and "plot" may possibly have different default options, but it seems that this is the case.

Arthur's answer provides a better alternatve to "hold on" I think.