Error when adding multiple legends to graph

Hello, I am trying to get a legend for the 10 tests I performed, but I am getting the error:

Error using legend (line 279)

Invalid argument. Type 'help legend' for more information.

This is my code:

xposition=(1:4:40);
yposition=zeros(length(xposition),1)+20;
pointsize = 15;
scatter(xposition, yposition, pointsize, HIT, 'filled')
axis([0,40, 0,40]);
grid on
colorbar
colormap("jet")
barnone=colorbar;
set(get(barnone,'Title'),'String','Hardness')
xlabel('X Axis Position (µm)')
ylabel('Y Axis Position (µm)')
q=[HIT(1);HIT(2);HIT(3);HIT(4);HIT(5);HIT(6);HIT(7);HIT(8);HIT(9);HIT(10)];
legend(q,'Test 1', 'Test 2', 'Test 3','Test 4', 'Test 5', 'Test 6', 'Test 7','Test 8', 'Test 9', 'Test 10');

What am I doing incorrectly? Thanks for your help!

[Walter Roberson]

What is HIT? In context it would have to be graphic handles to work

[birdnerd007]

HIT is a 10x1 array for one of my variables.

[birdnerd007]

It is the "hardness" value for the 10 tests that were performed.

[Walter Roberson]

What is it you expect legend() to do when you pass hardness values as the first parameter ?

[dpb]

"HIT is a 10x1 array for one of my variables."

Well as Walter points out, "that's just wrong!" The first argument to legend if not just text strings is and must be either subset or target, both of which are (and must be) graphics objects--the former a set of data series objects like line handles of those wanted on the legend if not all or an axes object of one kind or another for the latter.

See the documentation for the details.

Just taking q (you don't need it at all, removing that line would be good, too) out of the argument list should work; it's less typing to write something like

hLg=legend(num2str([1:numel(HIT)].','Test %d');

[birdnerd007]

dqb - That's exactly what I'm looking for; just one issue, only one blue dot appears as opposed to each of the colors corresponding to each test.

Walter - my apologies, I am still learning this stuff. I was hoping when I used the legend feature and calling my hardness, that it would allow me to name each test in the array. Again, I am probably not making sense because I still learning. Thanks for understanding.

[birdnerd007]

dqb - Do you know how I can get each color of dot to correspond with Test 1, Test, 2, etc? I appreciate your help.

Answer 1

[Star Strider]

The only way to do what you want is to plot each ‘HIT’ value individually in a for loop:

hold on
for k = 1:numel(HIT)
    q(k) = scatter(xposition(k), yposition(k), pointsize, HIT(k), 'filled');
end
hold off

then this works:

legend(q,'Test 1', 'Test 2', 'Test 3','Test 4', 'Test 5', 'Test 6', 'Test 7','Test 8', 'Test 9', 'Test 10', 'Loccation','N', 'NumColumns',2)

[birdnerd007]

You've been absolutely amazing today! Thanks for all of your help. I'm learning so much. Thank you again.

[Star Strider]

As always, my pleasure!