Why don't the markers have the correct color in the legend?

If you run this code you will understand what I mean by my question.

I would like that in the legend also the circles had the correct color, otherwise I would rather remove them altogether, leaving only the names.

A1 = randi(10, [5 5]);
B1 = randi(10, [5 5]);
A2 = randi(10, [5 5]);
B2 = randi(10, [5 5]);
scatter(A1,B1,'g');
hold on
grid on
scatter(A2,B2,'b');
title('TEST');
xlabel('X','FontSize',8,'FontWeight','bold');
ylabel('Y','FontSize',8','FontWeight','bold');
legend({'\color{green}G1','\color{blue}G2'},'Location','northwest');

savefig('./Figures/Test')

Error using save
Cannot create 'Test.fig' because './Figures' does not exist.

Error in matlab.graphics.internal.figfile.FigFile/write (line 33)
save(obj.Path, obj.MatVersion, '-struct', 'SaveVars');

Error in savefig (line 83)
FF.write();

Answer 1

[Les Beckham]

The problem is that each of your calls to scatter is creating five separate sets of data for a total of 10 sets. But, you only request the legend to be displayed for the first two.

From the documentation:

• To plot multiple sets of coordinates on the same set of axes, specify at least one of x or y as a matrix.

To illustrate what I mean, here is your example, but displaying the legend for all of the sets of data:

A1 = randi(10, [5 5]);
B1 = randi(10, [5 5]);
A2 = randi(10, [5 5]);
B2 = randi(10, [5 5]);
scatter(A1,B1,'g');
hold on
grid on
scatter(A2,B2,'b');
title('TEST');
xlabel('X','FontSize',8,'FontWeight','bold');
ylabel('Y','FontSize',8','FontWeight','bold');
legend

Depending on what you really are trying to do, you might just need to reshape or redefine your data as vectors instead of matrices.

Answer 2

[VBBV]

A1 = randi(10, [5 5]);
B1 = randi(10, [5 5]);
A2 = randi(10, [5 5]);
B2 = randi(10, [5 5]);
h1=scatter(A1,B1,'g');
hold on
grid on
h2=scatter(A2,B2,'b');
title('TEST');
xlabel('X','FontSize',8,'FontWeight','bold');
ylabel('Y','FontSize',8','FontWeight','bold');
legend([h1(1),h2(1)],{'G1','G2'},'Location','northwest');

[VBBV]

To display correct color for legend labels you can make use of function handles for scatter command as shown above. Then call the function handles in legend function

[Laura Gianolio]

Thank you very much because I solved my problem with your suggestion: calling the function handles in legend function.

legend([h1(1),h2(1)],{'G1','G2'},'Location','northwest');

I wanted to show in the legend only one row for each group of data contained in each individual pair of matrices.

Your explanation is very clear, you made me understand what my mistake was.

[Laura Gianolio]

Hello VBBV,

Another question: and if I wanted not to show the markers in the legend, but only the names, what should I do? Thanks!

[Les Beckham]

Why would you want to do that? Removing the markers from the legend makes the legend pretty much useless, in my opinion.

One way to present the data with no legend but still be able to identify which points belong to which dataset would be to use the yyaxis function.

A1 = randi(10, [5 5]);
B1 = randi(10, [5 5]);
A2 = randi(10, [5 5]);
B2 = randi(10, [5 5]);
yyaxis left
scatter(A1,B1,'b');
grid on
yyaxis right
scatter(A2,B2,'r');
title('TEST');
xlabel('X','FontSize',8,'FontWeight','bold');
ylabel('Y','FontSize',8','FontWeight','bold');

[VBBV]

@Laura Gianolio, Do you mean to display legend with the empty markers but still having the text colored ii.e. green and blue ?

[Laura Gianolio]

Exactly, that's what I wanted to say! Because for each dataset I use markers of different shape (to distinguish between different secondary datasets) but of the same color, so I want to identify the datasets in the legend only with the names of the right color.