For loop only accesses the last element in an array

Hi all,

I have an array CHANNEL[10 58 27], and I want my for loop to access all three elements. However, right now when I look at the value of di in my workspace, it says 27, so I'm assuming that it is only accessing the last element of the array.

How should I fix the code so that di accesses all three elements in the array?

for di=CHANNEL(1,:)
    %load (append('210603_bare-210727-182826','ch',string(di)))
    neural = timetable(RawData,'SampleRate',fs);
    neural.Properties.VariableNames{1} = 'raw';
    neural.Properties.VariableUnits{1} = 'Volts';
    HighPass = 300;
    LowPass = 5000;
    [Z, P, K] = butter(5, [HighPass LowPass]/(fs/2), "bandpass");
    sos = zp2sos(Z, P, K);
    neural.raw = double(neural.raw);
    neural.spikes = sosfilt(sos,RawData);
    
    for idx=1:length(CHANNEL)
        figure;
        nexttile;
        plot(neural.Time,neural.spikes(:,idx))
    end
    
    xlim([duration(0,init_mn,init_s,init_ms) duration(0,end_mn,end_s,end_ms)])
    ylim([-1e-4 1e-4])
end

[Stephen23]

"so I'm assuming that it is only accessing the last element of the array."

Rather than assuming things, you could check what the loop is doing:

for di = CHANNEL(1,:)
    disp(di)
    ..
end

"However, right now when I look at the value of di in my workspace, it says 27..."

Which is exactly what I would expect the value of di to have after the loop has finished:

1. on the 1st loop iteration it has value 10
2. on the 2nd loop iteration it has value 58
3. on the 3rd loop iteration it has value 27

The value from the last iteration remains in the workspace after the loop has finished.

[Soeun Lee]

Thank you for your comment. If di is accessing all three elements as you mentioned, then could you please let me know why I am obtaining three identical graphs when I plot plot(neural.Time,neural.spikes(:,idx))?

[Peter Perkins]

This post exactly duplicates https://www.mathworks.com/matlabcentral/answers/893447-why-do-i-obtain-identical-graphs-while-for-loop-is-accessing-different-sets-of-data-stored-in-differ.

[Stephen23]

@Soeun Lee: it might have something to do with your looping over the same vector in nested loops:

for di=CHANNEL(1,:)
    ...
    for idx=1:length(CHANNEL)
        figure;
        nexttile;
        plot(neural.Time,neural.spikes(:,idx))
    end
    ...
end

I very much doubt that that nested loop does what you expect or need.