Number of zeros in a matrix

I need to create a function where I have a matrix and the function returns the number of zeros in that matrix. I need to do this using the if condition.

Then write in a .txt file which columns had more than 12 zeros.

Can someone help me out with this?

Thank you very much.

Why did you need to do it with if condition?

Because thats what I usually work with but if thats impossible nevermind it.

Answer 1

The number of zeros in the matrix A is:

sum(~A(:))

So we can make this a function:

f = @(x) sum(~x(:));

Now test it:

x = [1 2 3;0 0 0;3 0 9]
f(x)

It works, awesome! Now to the hard part, how do I find out which columns have more than 12 zeros and then write that info into a .txt file?

Thank you.

What do you mean by write to a text file? You want to write only those columns that do or do not have more than 12 zeros? You want to write the whole column including all the zeros?

I want to write in a .txt file numbers of the columns that have more than 12 zeros. E.g. say I wanted the columns with atleast one zero. (Ignore the "if true" nonsense]

if true
  % code
end
M = 1 0 1 1
    1 1 1 0

I want the function to save a .txt file with the numbers 2 and 4.

M = [1 0 1 1;1 1 1 0]
fid = fopen('mytext.txt','wt')
fprintf(fid,'%i ',find(sum(~M) >= 1))
fclose(fid)

Thank you so much! Keep up the good work, cheers!

Answer 2

a - your matrix

number_columns = find(sum(~a) > 12);

Answer 3

numel(M) - nnz(M)