Cell2mat not working for high cell count

Hello, being trying to code Run length enc/dec on Matlab, and my work worked perfectly for test matrixes, but as soon as i tried 512x512 Matrix Cell2mat started giving me this error :

Error using cat

Dimensions of arrays being concatenated are not consistent.

Error in cell2mat (line 83)

m{n} = cat(1,c{:,n});

this is my code:

clear all;

%***reading a matrix x from the directory c:\

x=imread(['c:\mAT\512x512-No-Noise.jpg']);f=size(x);

c=1;

y={};

z=[];

for i=1:f(1)

y{i}=[];

for j=1:f(2)-1

if x(i,j)==x(i,j+1)

c = c + 1;

else

y{i}=[y{i} c x(i,j)];

c=1;

end

end

y{i} =[y{i} c x(i,f(2))];

c=1;

end

y

k=size(y);

z={};

for s=1:k(2)

a=size(y{1,s})

L=1;

z{s}=[];

while(L<a(2))

for n=1:y{1,s}(1,L);

z{s}=[z{s} y{1,s}(1,L+1)];

end

L = L+2;

end

end

new_z=cell2mat(z(:))

[Jan]

Please use a standard indentation: ctrl-a ctrl-i in the editor. This improves the readability.

Answer 1

[Jan]

This means, that the arrays stored in the cell do not have matching sizes. Check this:

sizeZ = [cellfun('size', z(:), 1), cellfun('size', z(:), 2)];
unique(sizeZ, 'rows')

Of course this is not a problem of cell2mat . Remember that this function is used for decades by many Matlab codes. It would be extremely surprising, if you find a bug in it...

An efficient method for expanding is repelem:

k = numel(y);
z = [];
for s = 1:k
    n = y{s}(1:2:end);  % Every 2nd element starting from first
    b = y{s}(2:2:end);  % ...starting from second
    z(s, :) = repelem(n, 1, b);
end

By the way, when I run your code with the test data:

x = randi([0, 255], 512, 512);

it does not cause an error.

[Adel Hafri]

my x matrix was 512x512 uint8 though