How to have MATLAB 2016 Legend without box and as transparent?

My proposal but I cannot get it work in MATLAB 2016b

 f = figure;
 hax = axes(f);
 [BL,BLicons] = legend(hax, 'lorem');

 % http://stackoverflow.com/a/26459062/54964
 PatchInLegend = findobj(BLicons, 'type', 'patch');
 set(PatchInLegend, 'facea', 0.5);

Syntax in Docs correspond to icons as `[lgd,icons,plots,txt] = legend(_)`.

Expected output: no box around the legend and transparency.

I have also tried unsuccessfully; which is what I have literally

 [BL, BLicons] = legend( bFigHax, sprintf('Tc'), 'Box', 'off', ...
    'Location', 'southwest', 'color', 'none');

MATLAB: 2016b OS: Debian 8.5

Answer 1

[Kirby Fears]

SL,

Check out the Matlab documentation on the legend function. Special arguments can be passed in as name value pairs when creating the legend. https://www.mathworks.com/help/matlab/ref/legend.html#namevaluepairarguments

The full list of names you can specify values for is here: https://www.mathworks.com/help/matlab/ref/legend-properties.html

The box can be removed by specifying

legend(...,'Box','off');

I don't see any options to make the legend background transparent, but you can change the background color using the 'Color' argument. The transparency setting you found on stackoverflow is specifically referring to the transparency of the green color patches displayed within the legend shown. If that's what you're after, their example should work.

[SL]

This does not work in my situation for some reason:`[BL, BLicons] = legend( bFigHax, sprintf('Tc'), 'Box', 'off', 'Location', 'southwest', 'color', 'none');`which is literally what I have.

[Kirby Fears]

SL,

Please describe what happens when you execute your legend command. What exactly is not working? There should at least be no boundary box.

Also, check that your other input arguments are valid. For example, are you trying to specify a single legend label 'Tc', because that's what you're specifying.

sprintf('Tc') % evaluates to string 'Tc'
ans = 
'Tc'

Have you verified that bFixHax is the correct axis handle?

Answer 2

[Afiq Azaibi]

Starting in R2024a, legend supports the ability to control the level of transparency with the BackgroundAlpha property. Below is a short example:

plot(magic(7));
grid on;
set(gca, 'Color', [.88 .88 .88]);
l = legend(BackgroundAlpha=.7);

Setting the value to 0 will make it fully transparent and a value 1 of will make it fully opaque which is the default behavior.

Rectangle also has a new FaceAlpha property and you can read more about both in this blog post.