How to find specific elements in cell array not followed by another specific element?

I have a cell array with the first column being events (redSquare, blueSquare, redButtonPressed, blueButtonPressed). I need to find the rows where redSquare is not followed by redButtonPressed and blueSquare is not followed by blueButtonPressed. I'm not really sure how to approach the problem without the logical NOT operator since it only works on numerical values (at least that's my understanding/experience). I would be extremely grateful or any help/direction. Thank you in advance!

[Walter Roberson]

What is class() of those? For example is it a cell array of character vectors? Is it a cell array of categoricals?

Is the entire cell array consisting of the same kind of things, such that you could categorical() the entire cell array, after which you could work with rows and columns of categoricals ?

[Mandy B.]

The first column with my events is a character vector, and then the other columns are of class double and contain times. There's many other events in my data, I'm just only looking at a few of them. Will using categorical still work in that scenario?

Thank you for your help also, I apologize if my questions are a bit dumb (I'm still learning)!

Answer 1

[Walter Roberson]

Assuming you used readtable() then

Events = YourTable{:,1};
G = findgroups(Events);

%The ids will be in sorted order.. provided you can be certain there are no
%other ids in the data. Otherwise you really should check the second output
%of findgroups()
G_blueButtonPressed = 1;
G_blueSquare = 2;
G_redButtonPressed = 3;
G_redSquare = 4;

mask = (G(1:end-1) == G_redSquare & G(2:end) ~= G_redButtonPressed)) | ...
       (G(1:end-1) == G_blueSquare & G(2:end) ~= G_blueButtonPressed));
row_idx = find(mask);

[Mandy B.]

Thank you!

Answer 2

[Peter Perkins]

If you have time and other data, think timetables (also Walter is right about categorical):

action = categorical([1;3;2;4;1;3;2;2;1;1],1:4,["redSquare" "blueSquare" "redButtonPressed" "blueButtonPressed"]);
value = rand(size(action));
time = seconds(1:length(action))';
tt = timetable(time,action,value)

tt = 10×2 timetable
     time          action           value  
    ______    _________________    ________

    1 sec     redSquare             0.40283
    2 sec     redButtonPressed      0.58469
    3 sec     blueSquare            0.25583
    4 sec     blueButtonPressed     0.21057
    5 sec     redSquare             0.68091
    6 sec     redButtonPressed      0.84098
    7 sec     blueSquare           0.002893
    8 sec     blueSquare            0.57486
    9 sec     redSquare             0.58551
    10 sec    redSquare             0.60419

action = tt.action(1:end-1);
reaction = tt.action(2:end);
badRedReaction = (action=="redSquare" & reaction~="redButtonPressed");
badBlueReaction = (action=="blueSquare" & reaction~="blueButtonPressed");
tt(badRedReaction|badBlueReaction,:)

ans = 3×2 timetable
    time       action       value  
    _____    __________    ________

    7 sec    blueSquare    0.002893
    8 sec    blueSquare     0.57486
    9 sec    redSquare      0.58551

[Mandy B.]

Thank you!