How to add axis labels while using for loops? Keep getting error: Index exceeds the number of array elements (4).

I am getting an error trying to add axis titles to my plot. I am using a for loop, but it is only letting me add a legend and a title.

this is the error message:

Index exceeds the number of array elements (4). Error in Homework_1 (line 12) xlabel('real')

z = [2 + 5i; 1.41+1.41i; 5.87+9.15i; -3.07+6.72i; 0.997+0.071i; 3*exp(1.23i); 2*exp((pi/2)*1i); 13*exp(1i); 3; 2+11i; 4+2i; (1/5)+(4/5)*1i;  ] ;
s = ['o'; '*'; 's'; 'p'; '+'; '>'; '<'; 'x'; 'd'; '.'; 'h'; '^';];

for index = 1:12
    plot (z(index), s(index), 'MarkerSize', 10 );
    hold on;
   
end
hold off;
title('complex numbers');
legend('2 + 5i', '1.41+1.41i', '5.87+9.15i', '-3.07+6.72i', '0.997+0.071i', '3*exp(1.23i)', '2*exp((pi/2)*1i)', '13*exp(1i)', '3', '2+11i', '4+2i', '(1/5)+(4/5)*1i');
xlabel('real');
ylabel('imaginary');

[woahs]

Not sure what the issue is here. The provided code executes without error. Your axis properties are set outside the loop so the fact that you used a loop to create them shouldn't matter.

[Kendall Noto]

when i run this script is does not add the labels to my resulting plot

while giving me this error message:

Answer 1

[Adam Danz]

Updated answer

It appears that you may have a variable named xlabel that is interfering with the xlabel() function. To confirm this, run the line below.

 which xlabel

If my hunch is correct, it should output: xlabel is a variable.

-----------------------------------------------------------------------

Old answer (still relevant)

As Kevin Chen mentioned, the code you shared does not result in any errors.

Here are 3 improvements to make.

1. Define number of iterations based on number of values available
2. Use DisplayName to label the legend

z = [2 + 5i; 1.41+1.41i; 5.87+9.15i; -3.07+6.72i; 0.997+0.071i; 3*exp(1.23i); 2*exp((pi/2)*1i); 13*exp(1i); 3; 2+11i; 4+2i; (1/5)+(4/5)*1i;  ] ;
s = ['o'; '*'; 's'; 'p'; '+'; '>'; '<'; 'x'; 'd'; '.'; 'h'; '^';];
% Define legend strings
legStr = {'2 + 5i', '1.41+1.41i', '5.87+9.15i', '-3.07+6.72i', '0.997+0.071i', '3*exp(1.23i)', '2*exp((pi/2)*1i)', '13*exp(1i)', '3', '2+11i', '4+2i', '(1/5)+(4/5)*1i'};
for index = 1:numel(z) % use z or s
    plot (z(index), s(index), 'MarkerSize', 10, 'DisplayName',legStr{index}); % use DisplayName
    hold on;
end
hold off;
title('complex numbers');
legend(); % just call legend()
xlabel('real');
ylabel('imaginary');

You could also move "hold on" outside of the loop.

[Kendall Noto]

Why does vector z and s only have 4 values when there are 12 in the array? sorry i am new to matlab

[Adam Danz]

Sorry for not being clearer. In the code you provided, z and s do have 12 values. But you would get that error if they only had 4 values.

[Kendall Noto]

when i execute the script in my matlab it is giving me an error as there only being 4 elements in the array, i am very confused why this is happening. I posted pictures above in Kevin Chen's comment on what it is looking like for me.

[Adam Danz]

Got it. See my updated answer.

[Kendall Noto]

okay what the heck, i just closed down my matlab and opened my script again and it worked perfectly... does that happen sometimes? it gets overloaded with data or something?

[Adam Danz]

No. If my hunch is correct, at some point a variable was created named xlabel and when that happens, you can no longer use the xlabel() function. Here's a demo

xlabel = 1:4; 
xlabel('real')
% error: Index exceeds the number of array elements (4).

% now, remove that variable
clear('xlabel')

If that variable exists in a script, you should search for it and remove it or rename it because it will cause the same problem again at some point. If you created that variable from the command window, then you're safe, just don't do it again ;)

[Kendall Noto]

Ohhh, i do remember now that i entered the xlabel wrong when i tried to do it at the very beginning. I understand now. Thank you so much for your help!!!

[Adam Danz]

One way to avoid these types of errors is to use functions rather than scripts. Functions have their own workspaces so if you accidentally created a variable named xlabel from the command window, it wouldn't exist within the function workspace the next time the function was run.

https://www.mathworks.com/help/matlab/matlab_prog/scripts-and-functions.html