When you call axis equal
, the axis box aspect ratio is fixed and the Position
property is treated as a maximum size. When you resize the figure window, the axis box will remain centered in the Position
rectangle, but in order to maintain the same aspect ratio as before, it may not take up the entire Position
rectangle.
If you want it to take up the entire Position
rectangle, you can call axis equal
again. (this may depend on your MATLAB version; it worked for me in R2015b).
This is also discussed in a bit more detail on MATLAB Central.
To answer your original question, it's a bit complicated. You'd have to get the plot box aspect ratio (using pbaspect()
or the axes PlotBoxAspectRatio
property) and figure it out:
ah = gca();
% Get the axes Position rectangle in units of pixels
old_units = get(ah,'Units');
set(ah,'Units','pixels');
pos = get(ah,'Position');
set(ah,'Units',old_units);
% Figure the PlotBox and axes Position aspect ratios
pos_aspectRatio = pos(3) / pos(4);
box_aspect = pbaspect(ah);
box_aspectRatio = box_aspect(1) / box_aspect(2);
if (box_aspectRatio > pos_aspectRatio)
% PlotBox is wider than the Position rectangle
box_height = pos(3) / box_aspectRatio;
box_dy = (pos(4)-box_height) / 2;
box_position = [pos(1), pos(2)+box_dy, pos(3), box_height];
else
% PlotBox is taller than the Position rectangle
box_width = pos(4) * box_aspectRatio;
box_dx = (pos(3)-box_width) / 2;
box_position = [pos(1)+box_dx, pos(2), box_width, pos(4)];
end
Note that this will give you the box position in pixels; if you want it in the normalized
units that are the axes default, you'll need to normalize it:
fig_pos = get(get(ah,'Parent'),'Position');
box_position = box_position ./ fig_pos([3 4 3 4]);
figure Z = peaks(20); contourf(Z,10) set(gca,'Units','pixels') get(gca,'position') axis equal get(gca,'position')
– Ivoryivorywhite