how do i do a for loop to find different array sizes

%say each matrix is

mode1 = [1 2 3];

mode2 = [4 5 6];

mode3 = [7 8 9 10];

mode4 = [11 12 13 14 15 16];

mode5 = [17 18 19 20 21];

%want to return the size of each one as k1 = 3, k2 = 3, k3 = 4, k4 = 6, k5 = 5

for i = 1:5

    f(i) = size(mode(i))
end

How can I fix this?

Thanks

Answer 1

[David Fletcher]

mode would have to be a cell array since the number of columns of each array is not the same i.e

mode{1} = [1 2 3];
mode{2} = [4 5 6];
mode{3} = [7 8 9 10];
mode{4} = [11 12 13 14 15 16];
mode{5} = [17 18 19 20 21];

for i = 1:5
    f(i) = length(mode{i}) %if they are always going to be vectors
end

For efficiency, you may also wish to consider pre-allocating the size of f

Instead of the length() function you could also use size() in the following ways:

for i = 1:5
    f(i) = size(mode{i},2) %if the are always going to be row vectors
end

or

    for i = 1:5
        [frows(i),fcols(i)] = size(mode{i}) %obtain both row and column size
    end

or

    for i = 1:5
        [~,fcols(i)] = size(mode{i}) %ignores the rows output from size function
    end

The loop could be omitted completely with

cellfun(@length,mode)