when output, matlab shows <missing>?

I wrote a recursive function to generate a car plate for each car

function plate=plates(n,plate)
if n<1
    return
else
    element=["1","2","3","4","5","6","7","8","9","0","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"];
    str1=element(randi([11,36]));
    for i=1:5
        str2=element(unidrnd(36));
        str1=strcat(str1,str2);
    end
    plate(n)=str1;
    plates(n-1,plate);
end
end

In my project, some of the cars are allowed to jump the red light, and I use an array 'jaywalk', whose original value is all 0, to record them:

if the car will jump the red light, jaywalk(1,i)=1;,i is the numerical order of the car

At the end of my project, I need to display the plate of the cars which jumpt the red light, n is the total number of cars

for i=1:n
    if jaywalk(1,i)==1
        disp(plate(i));
    end
end

BUT when I run the code to the stage of displaying the car plates, matlab shows missing.

how can i solve the problem?

Any help will be appreciated! Thanks!

[越琪 吴]

In my project, I use this to call out the function

plate=["0"];
plate=plates(n,plate);

Answer 1

[Walter Roberson]

plates(n-1,plate);

That is not an assignment statement.

[越琪 吴]

Thank you! And I modified it into

plate(n-1)=plates(n-1,plate);

but matlab says 'Unable to perform assignment because the left and right sides have a different number of elements.'

I really don't know how to modify that code, could you help me in detail? Thanks a lot!

[Walter Roberson]

What is the grammar for plates? Your existing code suggests that you start with a letter and then have 5 characters that are letters or digits. Why are you going recursive?

[越琪 吴]

yes, a car plate is composed of a letter and then 5 characters of letters or digits. I am going recursive because I need to generate a car plate for each of the n cars, I know this can be achieved by a loop, but recursion is demanded by my instructor. Thanks!

[Walter Roberson]

I suggest that you read https://www.mathworks.com/matlabcentral/answers/579063-code-for-reverse-a-vector#comment_998227