How to add extra information to figure's legend?

Question

I want to add extra Information to a figure in MATLAB, like this:

Is it possible? (Of course I want it to be more beautiful)

Permatron

You can use LaTeX in the legend labels, would that be sufficient? – Gaberdine

Yes, would you please give me LaTeX commands for this purpose? – Permatron

So, you want a headed table next to your legend? – Gaberdine

@RodyOldenhuis well, I would be interested in how to use latex\how to create a table within the legend... :) – Jaehne

@LuciusDomitiusAhenobarbus: not a table of course, but a pretty-printed list of parameter values next to each plot label. – Gaberdine

@RodyOldenhuis this wasnt meant to be critic, I'm really interested in this! – Jaehne

@LuciusDomitiusAhenobarbus: well, see my answer :) – Gaberdine

Answer 1

I put together something reasonably generic, see below.

I will generalize this a bit more and post it to the File Exchange, I think it's a fairly nice tool to have around :)

I intend to

• automatically adjust the table size to fit its contents
• make it suited for arbitrary legend placement
• couple the table and legend together when moving them with the mouse
• make the header optional
• support various types of input

But for now:

% Example input

plot(1,1,'r.', 1.1,1.1', 'b.', 1.2,1.2, 'k.');
legendHandle = legend('plot 1', 'plot 2 with longer title', 'plot 3');

tableHead = {'\theta_0' '\phi' 'df/dx'};
tableContent = rand(3);




% Extract information 
legendPosition = get(legendHandle, 'position');
children = get(legendHandle, 'children');
labels   = children(strcmp(get(children, 'type'), 'text'));


% Basic error traps
if size(tableContent,1) ~= numel(labels)
    error('LegendTable:dimension_mismatch',...
        'Each legend entry must have a corresponding row in the table.')
end

if size(tableHead,2) ~= size(tableContent,2)
    error('LegendTable:dimension_mismatch',...
        'Table header dimensions are inconsistent with table data.');
end

% Convert header & content to cell-array when necessary
if isnumeric(tableContent)
    tableContent = cellfun(@num2str, ...
        num2cell(tableContent), 'UniformOutput', false);
end
if isnumeric(tableHead)
    tableHead = cellfun(@num2str, ...
        num2cell(tableHead), 'UniformOutput', false);
end

% Proper tick locations for the table
xticks = linspace(0, 1, numel(tableHead)+1);
yticks = linspace(0, 1, numel(labels)+2);

% Text positions are in the centers of the table cells
txt_xPositions = xticks(1:end-1) + (xticks(2)-xticks(1))/2;
txt_yPositions = fliplr(yticks(1:end-1) + (yticks(2)-yticks(1))/2);

% Derive correct table position
headerHeight  = legendPosition(4)/numel(labels);
tablePosition = legendPosition + [0 -headerHeight 0 headerHeight];

% Shift position of original legend 
set(legendHandle, 'position', legendPosition + [-tablePosition(3) -headerHeight 0 0])

% Create table
table = axes(...     
    'position', tablePosition,...
    'xtick', xticks,...
    'ytick', yticks,...
    'xticklabel', [],...
    'yticklabel', [],...    
    'gridlinestyle', '-',...
    'box', 'on',...
    'tag', 'LegendTable');
grid on


% Print table header & table entries
kk = 1;
tableTexts = zeros(numel(tableHead)+numel(tableContent),1);
for ii = 1:numel(txt_xPositions)

    % Column header
    tableTexts(kk) = text(txt_xPositions(ii), txt_yPositions(1), tableHead{ii},...
            'parent', table,...
            'HorizontalAlignment', 'center');
    kk = kk + 1;

    % Column content  
    for jj = 1:numel(txt_yPositions)-1
        tableTexts(kk) = text(...
            txt_xPositions(ii), txt_yPositions(jj+1), tableContent{jj,ii},...
            'parent', table,...
            'HorizontalAlignment', 'center');
        kk = kk + 1;
    end 
end

Result:

Gaberdine

@SardarUsama i have this error with Matlab R2018a Error using imglegend (line 24) Each legend entry must have a corresponding row in the table. and Error using matlab.graphics.illustration.Legend/set Error setting property 'Position' of class 'Legend': Value must be numeric and finite – Standush

The behavior of legend seems to have changed in newer versions. With the same code, labels don't evaluate to what is intended (R2018a Update-2). The same can be achieved with labels = legendHandle.String; – Evidential

@SardarUsama now works. thank you, you were very kind and patient. I'm studying how the code works to understand – Standush

Answer 2

Well perhaps a bit of an overkill:

You could use uitable, like this

%define your data:
 dat =  {'        green', 1, 2;...
    '        blue', 2,3.1;...   
    '        yellow', 3, 4.8;}
columnname =   {' ', 'Param1', 'Param2'};
columnformat = {'char', 'numeric', 'numeric'}; 
t = uitable('Units','normalized','Position',...
        [0.05 0.05 0.755 0.87], 'Data', dat,... 
        'ColumnName', columnname,...
        'ColumnFormat', columnformat,...
        'RowName',[], 'Parent', gcf);

you just need to know the handle, if gcf (get current figure) doesnt work! you can then resize and do whatever you want, to make it look nice...

Jaehne

Answer 3

You can use the num2str function to pass parameters to the legend.

legend(['red ' num2str(param1_red) ' ' num2str(param2_red)], ... )

Volumed