Set aspect ratio in tilelayout

When I run this code, the two plots are not each "square" (aspect ratio 1:1)

function [] = plotSVD( A )
  A = [1, 2; 0, 2];
  theta = linspace(0,2*pi, 1000);
  x1 = cos(theta);
  y1 = sin(theta);
  tempBecauseMatlabIsStupid = A*[x1;y1];
  x2 = tempBecauseMatlabIsStupid(1,:);
  y2 = tempBecauseMatlabIsStupid(2,:);

  % Two plots
  tiledlayout(1,2) % Requires R2019b or later
  ax1 = nexttile;
  pbaspect(ax1,[1 1 1]); % doesn't do anything
  axis equal; % doesn't do anything
  plot(ax1,x1,y1)
  
  ax2 = nexttile;
  pbaspect(ax2,[1 1 1]); % doesn't do anything
  axis equal; % doesn't do anything
  plot(ax2,x2,y2)
end

Currently, to make them "square", I have to manually adjust the width of the window.

How can I make MATLAB print them "square"? Ideally, I'd like the figure to show in a window AND save to a PDF, with each of the two plots in the figure having an aspect ratio of 1:1

[Adam Danz]

"axis equal; % doesn't do anything"

axis equal does exactly what it's supposed to do - it equates the length of the data units along the axes.

What you're looking for is axis square which will equate the lengths of the axes but will not equate the axis units so a circle may not appear as a circle.

If you want both, you can set axis equal and then set the ylim and xlim ranges to be the same.

[Joseph Pedersen]

What I want is for the aspect ratio to be 1:1

Is that what you mean by "equates the length of the data units along the axes"?

If you look below, you'll see that the aspect ratio is not 1:1, even though I used:

daspect(ax1,[1 1 1]); % doesn't do anything

pbaspect(ax1,[1 1 1]); % doesn't do anything

axis equal; % doesn't do anything

[Adam Danz]

That's because you are applying it incorrectly.

"% doesn't do anything"

Those lines are doing exactly what they should be doing but you're losing those settings when you plot data to the axes.

See my answer for the correct way to apply these settings.

Answer 1

[Adam Danz]

You either need to apply the settings after plotting the data or you need to execute "hold on" after applying the settings, before doing the plotting. I suggest doing the prior.

tiledlayout(1,2) 
ax1 = nexttile;
plot(ax1,x1,y1)
axis equal;            % <---- move to after-plot
daspect(ax1,[1 1 1]);  % <---- move to after-plot
pbaspect(ax1,[1 1 1]); % <---- move to after-plot

or

tiledlayout(1,2) 
axis equal; 
daspect(ax1,[1 1 1]);
pbaspect(ax1,[1 1 1]);
hold on % <------- add this
ax1 = nexttile;
plot(ax1,x1,y1)

Demo: difference betwteen DataAspectRatio and Plot Box Asepct Ratio

When you set axis equal, the DataAspectRatio is set to [1 1 1] and the associated mode properties are set to manual. Also, the “stretch-to-fill” behavior is disabled. So, no need to set daspect when using axis equal.

pdadpect sets the plot box aspect ratio which is different than the DataAspectRatio. Here's a demo showing the difference:

Default axes within a figure that has been expanded horiziontally a bit. Note that the x and y ticks are the same but the grid does not form squares.

x = 1:20; 
y = x*.8; 
plot(x,y)
grid on
set(gca, 'XTick', 0:5:20, 'YTick', 0:5:20)

DataAspectRatio equal. Now the grid forms squares but the axis itself is not square. The x axis has a larger range than the y axis.

axis equal

Plot box aspect ratio equal. Now the axis is square as well.

pbaspect([1 1 1])

Note that this can also be achieved by setting the xlim and ylim to the same range. In fact, this method is often preferred and gives you more control over the range of values covered by the axes.

% instead of pbaspect([1 1 1])
xlim([0,20])
ylim([0,20])

[Joseph Pedersen]

Thanks! Putting the commands after plot worked.

I'm not sure if daspect(ax1,[1 1 1]); or pbaspect(ax1,[1 1 1]); did anything. It worked with just axis equal; on the line AFTER plot.

[Adam Danz]

I added to my answer to explain how axis equal and pbaspect differ. If something still doesn't make sense, I'd be happy to explain more.