Problems with saving vectors to cell array

Hello, newbie to Matlab here. I have a problem with saving vectors (which are not of the same length) to cell array. Let´s say I have a 2x8 matrix p and I access it´s cells via linear indices. I create vectors of pixels between p(1) : p(3) then p(5) : p (7) and p(9) : p(11). If I write this (e.g. vec = p(1) : p(3)) into command window I get the vector. What I try is to create these three (or more it depends) vectors and save them in cell array as follows:

rows = 0.5.*length(p);
k = 2.*length(p);

for i = 1 : 4 : k
    for j = 3 : 4 : k
        for m = 1 : rows
            p(i);
            p(j);
            M{m} = p(i) : p(j);
        end
    end
end

The problem is that the M-array created has 3 rows and every row contains the vector of same length (the last vector created, in my case p(9) : p(11)). What is wrong in my code that the output is this and not three rows containing three vectors as I desribed before?

I deal with this long time and finally I really dont know :( Thank you very much for your advices, Mari.

[the cyclist]

Can you please give an example of the matrix p, such that the code is self-contained and illustrates the problem?

Answer 1

[the cyclist]

I am not 100% clear on what you want to do, but here is a guess:

p = [1  2  3  4  5  6  7  8;
     9 10 11 12 13 14 15 16];

rows = 0.5.*length(p);
k = 2.*length(p);

rowCounter = 0;

for i = 1 : 4 : k
    rowCounter = rowCounter+1;
    j = i+2;
    p(i);
    p(j);
    M{rowCounter} = p(i) : p(j);
end

The main things that I have done are:

• Introduced some fake p data
• Removed the loop over j, because it seems that j is always determined by i, rather than being its own independent loop
• Removed the loop over m, because again this is really just counting rows, which is effectively done already in the one loop

I think the important thing to realize (if I have understood your intent correctly), is that you really only have one loop -- the starting value of your index -- and everything keys off of that.

I expect I don't have this quite right, but I bet it is closer to what you wanted to do.

[Mariana]

You understood my question very well and you have helped me also :) Very thank you, it works! I´m sorry I´m not skilled enough for such a things but I still learn.