Using forloop and whileloop to find if a number has appeared repetitively

This is a 13 x 2 vector where the first number is associated with a movie ID, and the second column is a actor ID who acted in this movie. Is there a way that I can compile 5698, 5699, 5700 (for example, I want it to be 5698 - 79543 80537 73975 79604). Would I need to a for loop and a while loop to do that? Something like:

for ii = 1:size(vector, 1)

while vector(ii) == vector(ii+1) ...

The goal of this is to check if the movie is an isolated, in which all of its actor has only acted in this movie, instead of appearing in other movies as well. For right now, I need to check all the actors associated with the same movie ID, and if they all have not appeared in other movies, then I would store this movie ID in an array.

5698 79543

5698 80537

5698 73975

5698 79604

5699 1348

5699 29926

5699 10084

5699 80351

5700 80093

5700 80092

5700 73392

5700 73579

5700 74767

Answer 1

[Dyuman Joshi]

You can also use groupsummary but since you mentioned loops, here a way with for loop -

Since the size of the groups differ, it's not possible to store them in a numeric array. You can save them in a cell array.

data = [5698 79543; 5698 80537; 5698 73975; 5698 79604; 5699 1348; 5699 29926; 5699 10084; 5699 80351; 5700 80093; 5700 80092; 5700 73392; 5700 73579; 5700 74767];
y = unique(data(:,1));
for i=1:numel(y)
    movie = y(i)
    actors = data(find(data(:,1)==y(i)),2)
end

movie = 5698

actors = 4×1

79543 80537 73975 79604

movie = 5699

actors = 4×1

1348 29926 10084 80351

movie = 5700

actors = 5×1

80093 80092 73392 73579 74767

[Rui Xu]

Thank you so much! This is so much easier than what I was thinking.

Since the size of actors is changing, is it possible to do a forloop to go through each of the elements in actors to check for repetition in another database?

What I am doing in this project is to find the movie that has actors that do not appear in other movies, so I would need to store the ID of the movie.

[Rui Xu]

In other words, is there a way that I can store the data as [5698 5699 5700] with the corresponding actors in an array as well?

[Awais Saeed]

You can use struct or cell array for this

[Dyuman Joshi]

"Since the size of actors is changing, is it possible to do a forloop to go through each of the elements in actors to check for repetition in another database?"

You can use unique() for them as well. If you want to save them, there are multiple ways (not sure which one you prefer)

data = [5698 79543; 5698 80537; 5698 73975; 5698 79604; 5699 1348; 5699 29926; 5699 10084; 5699 80351; 5700 80093; 5700 80092; 5700 73392; 5700 73579; 5700 74767];
y = unique(data(:,1));
for i=1:numel(y)
    z1{i,1} = y(i);
    z1{i,2} = data(find(data(:,1)==y(i)),2);
end
z1

z1 = 3×2 cell array
    {[5698]}    {4×1 double}
    {[5699]}    {4×1 double}
    {[5700]}    {5×1 double}

for i=1:numel(y)
    z2{i} = [y(i) data(find(data(:,1)==y(i)),2)'];
end
z2

z2 = 1×3 cell array
    {[5698 79543 80537 73975 79604]}    {[5699 1348 29926 10084 80351]}    {[5700 80093 80092 73392 73579 74767]}

Answer 2

[Awais Saeed]

Doing with loops is hectic. You should use find(). However, I did it with loops as you required. I added last two entires for my verification.

list = [5698       79543
        5698       80537
        5698       73975
        5698       79604
        5699        1348
        5699       29926
        5699       10084
        5699       80351
        5700       80093
        5700       80092
        5700       73392
        5700       73579
        5700       74767
        1200       99999
        5698       99999];

data1 = list(:,1)'; % movie id column
data2 = list(:,2)'; % actor id column

idx = [];
col = 1;
while(true)
    x = data1(col); % pick the first movie id and count its occurances
    for ii = 1:1:size(data1,2)
        if(data1(ii) == x)
            idx = [idx ii];
        end
    end
    s = sprintf('%u ', data2(idx));
    fprintf('actors acted for movie id = %d are: %s\n', x, s);

    % delete counted entries
    data1(idx) = [];
    data2(idx) = [];
    idx = [];
    
    if(size(data1,2) <= 0)
        break; % break out of while loop if there is no more data to loop through
    end
end

actors acted for movie id = 5698 are: 79543 80537 73975 79604 99999 
actors acted for movie id = 5699 are: 1348 29926 10084 80351 
actors acted for movie id = 5700 are: 80093 80092 73392 73579 74767 
actors acted for movie id = 1200 are: 99999 

[Rui Xu]

Thank you so much! This is so helpful!