How can I change the marker size in legend?

Hi, I am having a trouble with chaning the marker size in legned. I plotted some graphs as follows.

    plot(Model.Period,Model.QQ,'o','MarkerEdgeColor','k', 'LineWidth', 2, ...
        'MarkerFaceColor','none','MarkerSize',3);
    ylabel('Q(cms)','FontWeight','bold');
        hold on;
    area(Model.Period,Model.QQ, 'FaceColor',[.6 .9 .8],'EdgeColor','k');
        hold off;
    xlim([min(Model.Period) max(Model.Period)]);
    Graph.leg3 = legend('Q as o-symbol','Q as area plot');
    set(Graph.leg3,'Location','NorthEast', 'FontWeight', 'bold').

I want to increase the size of marker in the legend without changing the marker size in the graphs. Can you help me, please? Thank you.

[Ken]

You used to be able to do this. The kiddies keep changing things for the worse. Mathworks: Leave things alone if the alternative is reduced capability.

[RT5]

You still can change the marker size in the legend. You need to use the icons.Children.MarkerSize property of legend. Here is a link to a nice explanation:

http://stackoverflow.com/questions/32654300/how-to-increase-marker-size-of-the-legend-in-scatter-plot-in-matlab-2014b

Just tried this out in R2015b and works fine.

[Lauren Cook]

I just tried doing this with MATLAB 2014b with the following code

sz = 20:30:(20+30*5);  
[h,icons,plots,legend_text] = legend('1hour','3hour','6hour','12hour','24hour','Location','NorthWest');
  for i = 1:length(icons)
  icons(i).Children.MarkerSize = sz(i);
  end

|And I got the following error: |

No public field MarkerSize exists for class matlab.graphics.GraphicsPlaceholder.

    Error in plot_depth_qqplot_allDRTM (line 54)
    icons(i).Children.MarkerSize = sz(i);

I also tried this:

for i = 1:length(icons)
set(icons(i),'MarkerSize', sz(i));
end

And got this error:

Error using matlab.graphics.primitive.Text/set
There is no MarkerSize property on the Text class.

I am trying to set each marker size in the legend equal to the size in the figure. The size increases as the duration for that point increase (e.g., 1hr to 24 hrs). Is is actually possible to change the individual marker size in a legend? If so, what am I doing wrong? Thanks for any help.

[Walter Roberson]

sz = 20:30:(20+30*5);  

That is 6 entries

[h,icons,plots,legend_text] = legend('1hour','3hour','6hour','12hour','24hour','Location','NorthWest');

That has 5 legend entries. The mismatch is likely leading to difficulties.

Answer 1

[Shawn Daugherty]

This might be a roundabout way but in R2017b this works for me:

% Create a legend with 3 entries
[h,icons] = legend('Entry 1','Entry 2','Entry 3');

% Find the 'line' objects
icons = findobj(icons,'Type','line');

% Find lines that use a marker
icons = findobj(icons,'Marker','none','-xor');

% Resize the marker in the legend
set(icons,'MarkerSize',20);

Hope this helps.

[Walter Roberson]

I am not sure why your findobj() ends in -xor ? You would normally need another condition after that.

Perhaps,

icons = findobj(icons, '-not', 'Marker', 'none');

In a more general context where icons might be mixed objects,

icons = findobj(icons, '-property', 'Marker', '-and', '-not', 'Marker', 'none');

[Adam Danz]

Note that this solution uses undocumented outputs to legend() that have caused problems in recent releases of Matlab (since r2018b). For a full explanation of this problem, see this comment.

Answer 2

[Adam Danz]

How to create legend components that are customizable

Copy the plotted objects and replace their (x,y,z) coordinates with NaN values so the copied objects do not appear in the plot. You can change the graphics properties to the copied objects and use their handles to create the customizable legend.

Demo

% Create the plot
ax = axes(); 
hold on
h(1) = plot(linspace(1,5,25), rand(1,25), 'ro', 'DisplayName', 'foo');
h(2) = plot(1:5, rand(1,5), 'b-', 'DisplayName', 'bar');

% copy the objects
hCopy = copyobj(h, ax); 

% replace coordinates with NaN 
% Either all XData or all YData or both should be NaN.
set(hCopy(1),'XData', NaN', 'YData', NaN)
set(hCopy(2),'XData', NaN', 'YData', NaN)
% Note, these lines can be combined: set(hCopy,'XData', NaN', 'YData', NaN)
% To avoid "Data lengths must match" warning, assuming hCopy is a handle array, 
% use arrayfun(@(h)set(h,'XData',nan(size(h.XData))),hCopy)

% Alter the graphics properties
hCopy(1).MarkerSize = 15; 
hCopy(1).LineWidth = 2;
hCopy(2).LineWidth = 3; 

% Create legend using copied objects
legend(hCopy)

Note that some graphics objects have different property names for XData and YData.

Why you souldn't use solutions that rely on legend() outputs

Since r2018b only the first output of the legend function is documented. Archived documentation for the legend function from r2016a to r2018a suggests avoiding the use of the outputs other than the first output:

Note: This syntax is not recommended and creates a legend that does not support all graphics features. Use the l = legend(__) syntax to return the legend object and set Legend Properties instead.

For example, if the first and second outputs to legend() are both included, it interferes with the ability to change the fontsize of the legend text.

[Sim]

@Adam Danz if I use a "scatter" instead of a "plot"

h(2) = scatter(1:5, rand(1,5), 10, 'DisplayName', 'bar');

It does not recognise the MarkerSize

hCopy(1).MarkerSize = 15; 

How to make the trick you proposed, but with the "scatter" instead of "plot" ?

[Sim]

@Adam Danz I tried to use "SizeData" instead of "MarkerSize", but it does not work:

for i = 1 : 2
    hCopy(i) = copyobj(h1(i), ax); 
    set(hCopy(i),'XData', NaN', 'YData', NaN)
    % hCopy(i).SizeDataMode = 'manual';
    hCopy(i).SizeData = 15;
end

[Adam Danz]

@Sim, you must be using scatter objects. Since a single scatter object can have varying marker sizes, the size of the marker in the legend does not represent a particular marker size.

Instead of copying scatter objects, just use plot to create the legend symbol.

Example:

h = scatter(6:-1:1,1:6,50:50:300,'bo');
ax = gca();
hold on

% Create legend marker
hCopy = plot(nan,nan,'bo','MarkerSize',20,'DisplayName', 'foo');
legend(hCopy)

[Sim]

Super!!! Thanks a lot @Adam Danz !! :-)

[Sim]

@Adam Danz Me again, Hi! ...What if I want slightly transparent symbols in the legend. Indeed, I can set transparency for scatter:

scatter(x,y,'o','MarkerEdgeAlpha',0.2)

but I cannot do the same for plot...right?

Any workaround to add transparency to the legends symbols, and still using your method?

[Adam Danz]

Transparency for line objects is not fully supported and does not have a property similar to MarkerEdgeAlpha. Instead of copying the axes objects and duplicating them for the legend, you could replace the line object with a scatter object that has the same color and size but applies MarkerEdgeAlpha.

Answer 3

[Jeffers]

A brute force (not very elegant) kind of thing I often do (Matlab 2015b, but should work in all) is to create a new plot of a single point (on the same figure) with the same marker type and the size you require in the legend. Just make sure the point doesnt show up in your graph (e.g. by controlling the axis limits using axis([xmin xmax ymin ymax])).

E.g.

plot(4:1:8,1:2:9,'x','MarkerSize',10,'Color',[1 0 0]);

hold on;

axis([0 9 0 9]);

p=plot(100,100,'x','MarkerSize',50,'Color',[1 0 0]);

l=legend(p,'Big Marker','Location','NorthWest');

set(l,'Interpreter', 'latex','FontSize',20);

Of course, you can do this with several different types of data point (marker), where 'p' becomes a vector e.g. p(1)=plot();p(2)=plot();...

[Walter Roberson]

You can use nan or inf for the point coordinates to ensure it will not render the points without having to adjust the plotting limits.

Answer 4

[Ramalingam Kailasham]

legendmarkeradjust does not give a satisfactory performance with R2017b. The legend markers are of a different style from the figure. LaTeX interpretation also seems to be a problem. Shouldn't there be a simpler way to adjust the legend marker size??!

Answer 5

[Jing Ci Neo]

I find that this works. For example if I want to change the symbol size of the second and third symbols:

[hLg, icons]=legend('Lines','A','B','C');

icons = findobj(icons,'Type','patch');

icons = findobj(icons,'Marker','none','-xor');

set(icons(2:3),'MarkerSize',11);

[Walter Roberson]

I am confused about the purpose of the -xor that is not followed by a condition?

[Jing Ci Neo]

I must admit I have no idea and I'm curious about it as well. Both "-or" and "-xor" works, and both "-and" and "-not" does not work

[Hannes Schwingenschlögl]

is there a possibility of getting the variable "icons" out of an existing legend without creating a new one?

[Walter Roberson]

No. When the icons output is requested, legend builds the internal structure differently. The properties do not exist in a way that can be changed when icons is not used.

[Samuel Nathan]

This Code worked perfectly in 2019b.

[Adam Danz]

As Walter pointed out, this solution uses udocumented outputs to legend() that have caused problems in recent releases of Matlab (since r2018b). For a full explanation of this problem, see this comment.

[Ritam]

This worked perfect on MATLAB R2022b. Thank you so much :)

Answer 6

[Sachin Ganjare]

Refer below link:

http://www.mathworks.com/matlabcentral/newsreader/view_thread/240826

Hope it helps!!!

[Hwee]

I added:

a=get(Graph.leg3,'children'); set(a(1),'MarkerSize',20);

based on your suggestion. But still it does not works. Can any one give me the method to solve this problem?

Thank you.

[Sachin Ganjare]

Did you tried the solution mentioned at the end of thread I shared?

[Hwee]

Yes, I tried but it does not work.

[Sachin Ganjare]

Probably below link helps:

http://stackoverflow.com/questions/4151221/change-the-size-of-a-fill-sample-in-matlab-legend

It shows usage of 'Position' property for legend resizing

[Hwee]

I only need to how to change the marker size in legend not fontsize and the box size of the legend. Thank you for your help but it does not solve my problem.

[Sachin Ganjare]

I think your 'ShowHiddenHandles' property is 'OFF'. Probabaly switching it to ON & then applying solution in thread will help.

[Hwee]

How can I turn on 'ShowHiddenHandles' property?

[Sachin Ganjare]

plot_handle = plot(Model.Period,Model.QQ,'o','MarkerEdgeColor'.....

set(plot_handle, 'ShowHiddenHandles', 'on')

[Hwee]

it does not work

Answer 7

[Lionel Trébuchon]

I am interested too! Neither "children" nor "findobj" seem to work in Matlab 2015b!

Friendly greetings, Lionel

Answer 8

[Andreas]

The function adjust legend marker size has now been updated to work with Matlab 2016b http://www.mathworks.com/matlabcentral/fileexchange/46105-adjust-legend-marker-size

Answer 9

[Azzi Abdelmalek]

h=legend(text')
set(h,'fontsize',20)

[Hwee]

this changes only the size of text in legend.

[Azzi Abdelmalek]

set(h,'fontsize',20,'Position', [.1,.2,.1,.2])

adjust your position

[Hwee]

I think you do not understand my point.

[Azzi Abdelmalek]

can you explain?

[Hwee]

I am trying to change the marker size in the legend.

[Azzi Abdelmalek]

t=0:0.1:10
y=sin(t)
plot(t,y)
ax2=axes
plot(0,0,'linewidth',10,'parent',ax2)
legend(ax2,'txt')
set(ax2,'visible','off')

Answer 10

[Andreas]

Try this function I made http://www.mathworks.com/matlabcentral/fileexchange/46105-adjust-legend-marker-size

[Matthew Cooper]

Thanks Andreas that is a great function.

[Luis Pazos]

Hi Andreas,

Do you know if this script still works? I have tried it in the last version of matlab, and doesn't seem to be able to find any children for legend.

I paste the response of the first four lines of you code in my figure:

Input:

s=get(legend)
s1=s.Children
s2=[]
s2=findobj(s1,{'type','patch','-or','type','line'})

Output:

s =

                   Box: 'on'
                 Color: [1 1 1]
             EdgeColor: [1 1 1]
              FontName: 'Cambria'
              FontSize: 32
             FontAngle: 'normal'
            FontWeight: 'normal'
           Interpreter: 'tex'
             LineWidth: 0.6000
              Location: 'northeast'
           Orientation: 'vertical'
              Position: [0.5988 0.6667 0.2943 0.1901]
                String: {'Sqrt(PL) = n(x)'  'Photocurrent'}
             TextColor: [0 0 0]
                 Units: 'normalized'
              Children: []
                Parent: [1x1 Figure]
               Visible: 'on'
      HandleVisibility: 'on'
         UIContextMenu: [1x1 ContextMenu]
            BusyAction: 'queue'
          BeingDeleted: 'off'
         Interruptible: 'off'
             CreateFcn: ''
             DeleteFcn: ''
         ButtonDownFcn: @bdowncb
                  Type: 'legend'
                   Tag: 'legend'
              UserData: []
              Selected: 'off'
    SelectionHighlight: 'on'
               HitTest: 'on'
         PickableParts: 'visible'

s1 =

0x0 empty GraphicsPlaceholder array.

s2 =

     []

s2 =

0x0 empty GraphicsPlaceholder array.

I also attach the figure in which I'm applying this. What I would need is basically to make the lines of the legend larger, because at the moment they are disproportionately small compared to the letters. I would really appreciate help with this.

Thanks in advance, Luis

[Walter Roberson]

As of R2014b, legend no longer have children.

Answer 11

[Ioannis Matthaiou]

hi, has anyone found a solution as to how to adjust markersize property of the legend in matlab 2015b? thanks, yiannis