How to extract number of matrices with all elements zero and the indexes of those matrices in a struct

Hi

I want to obtain the number of zero or nonzero matrices and their indexes in a struct like in the figure on the left. I am trying to check the cov named matrix in the right figure which are in all 1x1 struct cells on the left figure.

Thank you

Answer 1

[Voss]

% making up some data like yours:
gridcell_meancov = struct('grid',struct('mean',num2cell(rand(12,6)),'cov',squeeze(num2cell(randi([0 1],[2 2 12 6]),[1 2]))))

gridcell_meancov = struct with fields:
    grid: [12×6 struct]

gridcell_meancov(1).grid

ans = 12×6 struct array with fields:
    mean
    cov

% obtain which "cov" matrices are all zero:
cov_all_zero = ~cellfun(@(x)any(x,'all'),{gridcell_meancov(1).grid.cov})

cov_all_zero = 1×72 logical array
   1   0   0   1   0   0   0   0   0   0   0   0   0   1   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   1   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   1   0   0   0   0   0   0   0   0   0   1   1   0   0   0   0   0   0   0   0   0   0   0   0

% the number of all-zero cov matrices:
n_all_zero = nnz(cov_all_zero)

n_all_zero = 7

% the indexes of those all-zero cov matrices:
idx_all_zero = find(cov_all_zero)

idx_all_zero = 1×7

1 4 14 31 49 59 60

% the number of not-all-zero cov matrices:
n_not_all_zero = nnz(~cov_all_zero)

n_not_all_zero = 65

% the indexes of those not-all-zero cov matrices:
idx_not_all_zero = find(~cov_all_zero)

idx_not_all_zero = 1×65

2 3 5 6 7 8 9 10 11 12 13 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 32 33 34

[AKAYDIN]

Thank you for your answer

[Voss]

You're welcome!

Answer 2

[Paul]

Hi Abdullah,

The Question use the term "cell" but it looks like the data only uses structures. If that's the case, then ....

Create some example data

gridcell_meancov(1).grid(1,1).mean = 0;
gridcell_meancov(1).grid(1,1).cov = zeros(2);

gridcell_meancov(1).grid(1,2).mean = 0;
gridcell_meancov(1).grid(1,2).cov = eye(2);

gridcell_meancov(1).grid(2,1).mean = 0;
gridcell_meancov(1).grid(2,1).cov = zeros(2);

gridcell_meancov(1).grid(2,2).mean = 0;
gridcell_meancov(1).grid(2,2).cov = eye(2);

The result

sum(arrayfun(@(S) all(S.cov==0,'all') ,gridcell_meancov(1).grid),'all')

ans = 2

If I've misinterpreted the arrangment of the data, then post a small example that illustrates the data you have.

[AKAYDIN]

Thank you for your answer