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.

[Azzi Abdelmalek]

Why did you need to do it with if condition?

[Bob Choy]

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

Answer 1

[Matt Fig]

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)

[Bob Choy]

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.

[Matt Fig]

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?

[Bob Choy]

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.

[Matt Fig]

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

[Bob Choy]

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

Answer 2

[Andrei Bobrov]

a - your matrix

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

Answer 3

[Walter Roberson]

numel(M) - nnz(M)