legendflex: a more flexible legend

Create a legend with more flexible positioning and labeling capabilities

Description

With legendflex, you can:

- position the legend relative to any object in any figure, not just the parent axis of whatever is being labeled
 
- organize legend text and symbols in a grid with a specified number of rows and/or columns

- rescale the horizontal space used by each legend symbol
    
- create multiple legends for the same axis
    
- add a title to the legend within the legend box

Acknowledgements

Setpos 1.2 Getpos 1.2 inspired this file.

• MATLAB release: MATLAB 7.10 (R2010a)

[Tobias Benjamin Gram]

Great addon to Matlab. Especially the shrinking function removing the unwanted space between legend marker and legend text. Thanks

[James Ackman]

Indeed, this function allows for flexible positioning of legend data without auto-resizing of your plot axes.

And as a bonus it is a great way to make a static legend-- as workaround for the often discussed problems of slow graphics performance when updating dynamic plot data with the base legend() command.

[James Ackman]

 

[Kesh Ikuma]

Thanks for sharing a very useful function!

I have one issue though. I'm creating an EPS figure using the built-in PRINT function (in conjunction with my submitted EPS Toolbox), and the legendflex texts overlap while built-in legend gets the exact same texts properly resized. It appears to be that the print resolution is not reflected properly (96 desektop dpi to e.g., 300 print dpi) Any clue how to work around this? If you'd like to see what I described, please contact me via email. Thanks!

[Henrik]

Thank you very much Kelly, this fixed the problem

[Kelly Kearney]

@Henrik: Technically, legends are axes (both regular legends and those generated by legendflex). It looks like Convert4publication.m filters out legends based on their Tag property (on line 153). If you add the following line in the same location, it should also filter out legendflex axes:

h(arrayfun(@(a) isappdata(a, 'legflex'), h)) = [];

[Henrik]

Hi
This is exactly what I have been looking for to help make nice plots. However, I have a problem with this function in combination with convertplot4publication: http://www.mathworks.com/matlabcentral/fileexchange/34741-convertplot4publication
I'm hoping you could be able to help me with this?
For some reason it sees the legend as a subplot.. Here's an example of the problem:

y1 = randn(1000,1);
plot(y1)
legh={'leg1'};
legendflex(legh,'xscale',0.5)
ConvertPlot4Publication('testPlot')

[Kelly Kearney]

@Leo,

The warning you are receiving is one issued by the print function whenever it prints a figure with a ResizeFcn, and legendflex does add a resize function to figures. Setting your figure's 'PaperPositionMode' to 'auto' will avoid it (and save you the step of manually setting the page size). Or you could use a function like export_fig (FEX #23629), which in my opinion produces much better output without the quirks of print.

[Leo Simon]

Thanks very much for this program, it's very helpful. I'm having one problem, which may or may not be specific to legendflex. I'm using it to print my legend to a separate figure. I want to resize my legend to be the same size as a regular figure. I can do this on screen with

set(gcf,'Position',...);

To match on paper what I have on screen I would normally use

set(gcf,'PaperPosition',...);

But when I set 'PaperPosition' to the desired size, to preseve the larger sized legend, and then print, I get this message:

Warning: Positioning Figure for ResizeFcn. Set PaperPositionMode to 'auto' (match figure screen size) to avoid resizing and this warning.

I've never had this problem before, so wondering if it's something special about legendflex.

Any advice would be most appreciated!

Leo

[Kelly Kearney]

A workaround for the vertical positioning issues with subscripts/superscripts pointed out by William: render the legend with Interpreter set to 'none', then reset it to 'tex' afterwards. You may need to use a larger text size on the initial render as well, and reset to the correct size afterwards (e.g. if text hits box). It's not a perfect fix, and introduces extra horizontal space between columns, but I haven't found a better way to deal with the issues of produced by tex formatting in legends.

[William]

This is exactly what I was looking for, thank you! It worked perfectly for the first application (legends in subplots).

When I tried to use it the second time, I noticed a bug. When I used the legend with subscripts, e.g., 'e_pp', the marker positions are shifted downward. Is there anyway to correct this?

Thanks again, I appreciate your work!

[Eric]

I am running into issues when using the PRINT command as follows:

print(fig,'-depsc2','-r600',fname.eps)

It creates the eps fine but the legend boxes are not in th eproper location. I can fix that be setting the figure PaperPositionMode to 'auto', but I like to have the flexibility of resizing before I print. Also, sometimes (like with a single row legends, the end of the text is clipped by the legend box.

[Eric]

I am running into issues when using the PRINT command as follows:

print(fig,'-depsc2','-r600',fname.eps)

It creates the eps fine but the legend boxes are not in th eproper location. I can fix that be setting the figure PaperPositionMode to 'auto', but I like to have the flexibility of resizing before I print. Also, sometimes (like with a single row legends, the end of the text is clipped by the legend box.

[alexancer]

 

[Clint Noack]

 

[Erik Johnson]

If legendflex is called like:

[legend_h, object_h, plot_h, text_str] = legendflex(h, strs, 'ncol', ncols, ... );

then a workaround for the column offset is:

% fix legendflex's subsequent column locations
h = findobj(object_h, 'type', 'line');
y = get(h, {'YData'});
y = repmat(ans(1:ceil(length(y)/2/ncols)*2,:), ncols, 1);
y = ans(1:length(h),:);
set(h, {'YData'}, y);

[Erik Johnson]

A VERY useful function. However, I get slight offsets in the vertical locations of the lines/markers in different columns. Have you seen this?

For example, the code:

nrows = 1;
ncols = 3;
n = nrows * ncols;
x = repmat([0;1], 1, n);
y = [zeros(1,n); (1:n)/n];
h = plot(x, y);
strs = num2cell(char('`'+(1:n)), 1)';
[legax,legh] = legendflex(h, strs, 'ncol', ncols);

get(findobj(legh,'type','line','LineStyle','-'),{'YData'});
cat(1,ans{:}); yline=reshape(ans(:,1),[],3)
get(findobj(legh,'type','line','LineStyle','none'),{'YData'});
cat(1,ans{:}); ymarker=reshape(ans(:,1),[],3)
get(findobj(legh,'type','text'),{'Position'});
cat(1,ans{:}); ytext=reshape(ans(:,2),[],3)

gives the results:

yline = [9.5388 9.2710 9.0032]
ymarker = [9.5388 9.2710 9.0032]
ytext = [4.3091 4.3091 4.3091]

showing that the text items are set at consistent locations, but the lines and markers are slightly offset. (Change nrows to, say, 8 and the same vertical offset happens on all elements of subsequent columns.)

Any suggestions?

P.S. This is in MATLAB 7.14.0.739 (R2012a) on a Mac.

[Chris]

Very nice - thanks!
I wonder if anyone knows how to go a step beyond. That is, my legends are often like tables which I currently hand make as figures within figures. The table-like legend has row and column headings with only the symbols/line types in the cells instead of a label for every symbol/line. This is because the symbol itself might change to represent one variable and whether it's filled or open might represent another so it's identity is a combination of the row and column headings in the table.

[Dominic]

 

[Camille Couzi]

thanks a lot for this very useful code!!!

[Mukhtar Ullah]

Thanks Kelly for your explanation. I am not sure what will I loose if I keep those lines commented out. At the moment, I am avoiding any figure resize when both legendflex and panel are at play.

[Kelly Kearney]

@Mukhtar Ullah

Regarding making legendflex play nicely with panel, I admit I never considered the possibility that a figure's resize function might be linked to an object method. I don't do object-oriented coding myself, so I have very little knowledge of the internal workings, scope, etc. of objects. So no promises to fix this, though I will look into it if I find some spare time.

[Mukhtar Ullah]

I just realized that it is possible to find the legendflex axes by
ax = getappdata(hfig, 'legflexchildren')
I now have another problem. When I use legendflex together with panel
http://www.mathworks.co.uk/matlabcentral/fileexchange/20003-panel
any attempt to resize the figure results in the following error
Error using panel.resizeCallback
Cannot access method 'resizeCallback' in class 'panel'.

Error in legendflex>resizefig (line 637)
feval(Lf.oldrsz, hfig, ed);

Error using drawnow
Error while evaluating figure ResizeFcn

It turned out that commenting line 637 solves my problem.
Any idea of fixing this in a future release?

Thanks

[Mukhtar Ullah]

Thank you Kelly for clarifying that. It occurred to me because with legend, it is possible to set properties such as interpreter, string,..using set directly on the axes handle.
A minor addition to legendflex will make it easier to find its handle using findobj and findall function. For example, if you add a tag 'legendflex' to the axes, findobj(gcf, 'tag', 'legendflex') would locate the axes.

Mukhtar

[Kelly Kearney]

@Mukhtar Ullah,

I don't actually manually set the interpreter in this function, so it relies on the default. You can actually change this after the fact using set, as long as you return the object_h handles (see last syntax option); the first n indices of this array will correspond to the n text objects in the legend. This slightly obscure way of returning handles was chosen to be consistent with the original legend command.

[Mukhtar Ullah]

This function is the first serious fix to the long lasting problems Matlab has with legends.
The text interpreter is set none by this function and you could only change it when calling the function, and not later using SET. Is there a good reason for that?
Mukhtar

[Ben]

Could you provide the example of getting the result as the screenshoot shows? I think the simple examples in the .m file is not fully demonstrate the capability of your function. Wish you could add more examples.

[Philipp]

 

[Mario Liverpool]

Very useful indeed!

[Kelly Kearney]

Vertical alignment bug has been corrected, and I added some checks to make sure the figure resize doesn't crash when you remove a legend. Thanks to Jason for discovering these bugs.

[Jason Kaeding]

I guess it didn't take my first bug submission...

The vertical positioning of the patches is incorrect in the following code:

figure;
area(1:10,rand(10,10))
legendflex(gca,cellstr(num2str(column(1:10))),'ncol',5,'anchor',[6 2],'buffer',[0 -10])

[Jason Kaeding]

Another bug: if I delete the legend then resize my figure, I get an error...

??? Error using ==> getappdata
Invalid object handle

Error in ==> legendflex>resizefig at 621
Lf = getappdata(ax(ia), 'legflex');

??? Error while evaluating figure ResizeFcn

[Claudio]

Well done! Very useful!

[Dan]