Common legend for each row of tiled layout

I am trying to make a compact tiled layout with N rows and 2 columns where the axes of each row share a common legend in MATLAB R2023b. The legend should be positioned above and in between the two axes in each row. I have attempted to do this by adding a legend to one tile in a row, and then repositioning it. However, this changes the size of the axes and causes the legend to overlap the axes

Here's a MWE:

%% Generate the tiled layout and legends
tlh = tiledlayout(2,2,'TileSpacing','Compact');

% Tile 1
nexttile
plot(rand(20,2))

% Tile 2
nexttile
plot(rand(20,2))
lh = legend('sample 1','sample 2');

% Tile 3
nexttile
plot(rand(20,2))

% Tile 4
nexttile
plot(rand(20,2))
lh(2) = legend('sample 3','sample 4');

% Adjust Legend parameters
[lh.Location] = deal('NorthOutside');
[lh.Orientation] = deal('horizontal');
[lh.Units] = deal('normalized');

This looks ok, with nicely-sized plots, but we want the legends to be in the centre.

%% Reposition the legends

for i = 1:length(lh)
    lw = lh(i).Position(3);
    lh(i).Position(1) = 0.5-lw/2;
end

This makes the legends overlap the axes.

What to do? I can't use the "Layout" options in the legend handle as far as I know; that would only let me place on axis above the figure. I can't change the position of the axes, as these cannot be set manually in a TileChartLayout.

I could do nested tiled layouts, but that seems very cumbersome, especially when I have many more rows.

Thank you

Answer 1

[Matt J]

I could do nested tiled layouts, but that seems very cumbersome, especially when I have many more rows.

Why?

%% Make Layout Skeleton
[ax,t]=makeLayout(5,4);

%% Populate Axes
for k=1:numel(ax); plot(ax(k), rand(20,2)); end 

%% Populate Legends
for i=1:numel(t)
       Strings=compose("sample %d.%d",i,1:2);
       lh(i) = legend(t(i).Children(1),Strings,'Orientation','horizontal','Units','normalized');
       lh(i).Layout.Tile='north';
end

function [ax,t,T]=makeLayout(nrows,ncols)

    T = tiledlayout(nrows,1,'TileSpacing','Compact');
    k=0; 
    for i=1:nrows
       t(i)=tiledlayout(T,1,ncols,'TileSpacing','Compact');
       t(i).Layout.Tile=i;   
       for j=1:ncols
           k=k+1;
           ax(k)=nexttile(t(i));       
       end       
    end 

end

[Delyle Polet]

Thanks! This is what I need

Answer 2

[Image Analyst]

Did you try title or sgtitle?

[Delyle Polet]

The question asks for a common legend between axes. Is there a way to use title to accomplish this?