my for loop doesn't seem to be working. I want to add the correct letter to a string based on the equality of two arrays. How can I make this wok?

dec = table2array(decodeMessage);
ix = -40:3:38;%collating the degrees corresponding to the letters
message = "";
al = "abcdefghijklmnopqrstuvwxyz ";%corresponding letter array
volm = zeros(1,16);
in = 1;
for j=1:1:16
    volm(j) = mean(dec([in:in+14],2));
    in = in+15
end
% have collected average values in volm
degm = (volm-co(2))/co(1);% making x the subject of y=mx+c
round(degm);
%rounded to the nearest integer, now we have our final values

%% this is where it stops working, how do i fix this? the message string is blank


for k = 1:16
    for o = 1:27
        if ix(o) == degm(k)
            message = message+ al(o);
        else
            continue
        end
    end
end

[Natalia Mehta]

I didn't get any errors, but I haven't gotten the desired output.

[Clayton Gotberg]

I caught the second error you'd get, but not the first one.

In line 13, you say round(degm). However, you never save the results of this action. If you want to use degm as the rounded values, you have to save the results to degm. For example, degm = round(degm);. Otherwise, MATLAB saves the output of the round() function to the variable ans.

[Natalia Mehta]

Thank you so much! Turns out that it was because i didn't save degm to a variable, my bad ahah

[Clayton Gotberg]

I can safely say we've all been there! After all, I missed it in my first reading too. I'm glad I could help.

Answer 1

[Clayton Gotberg]

It seems the problem is that al is a string and therefore counts as one object for MATLAB. You can remedy this by switching to a char array (using single quotes instead of double quotes) or by splitting the string into an array of strings.

single_string = "abcdefghijklmnopqrstuvwxyz "; % 1x1 object so can't be indexed

% Solutions:
string_array = ["a" "b" "c" "d" "e" ... ]; % And so on
% or
char_array = char("abcdefghijklmnopqrstuvwxyz ");
% or
char_array = 'abcdefghijklmnopqrstuvwxyz ';

I bet your error was something like "Index exceeds array bounds". Please make sure you include any errors when you make your post so we can help you as much as possible!

[Natalia Mehta]

I tried this too, and I didn't get a string. There were no errors, but I did not get the desired output.

[Clayton Gotberg]

If your code evaluates without issue but the message string is still blank, check your logic everywhere else. For example, in the code it's never declared what co is. Additionally, if you intend to use the rounded values of degm you need to save them to a variable.

degm = (volm-co(2))/co(1);% Step 1
round(degm); % Step 2
disp(degm)
% Will show that degm isn't changed from Step 1
% but
degm = (volm-co(2))/co(1);% Step 1
degm = round(degm); % Step 2
disp(degm)
% Will show that degm is now only integers.

[Natalia Mehta]

My apologies for not including the value of co(), it's something i used earlier in the program.

[Clayton Gotberg]

That makes sense. If after all of this you're still not getting an output, can you attach the code or a workspace after you run the code to a comment? I can dig a little deeper into the variables and see if there's something else causing the problem. My gut instinct is that there's a problem with the if ix(o) == degm(k) part of the code.