CODEWITHSUNDEEP
arraysmatlab
ddjfjfj djfiejdn
ddjfjfj djfiejdn

Reputation: 131

How can I count the specific values of an array in MATLAB?

Here is a 10x10 array arr.

This arr has 100 elements. And it has distribution from -10 to 10 and there are 5 0-value.

I did this code because I wanted to know the number of 0.

count = 0;

for i = 1: 10
     for j = 1: 10
         if (arr (i, j) == 0)
             count = count +1;
         end
     end
end

Logically, count should be 5 in MATLAB's workspace. and i and j are 10.

However, when I run the code, count is 0.

This code can not count the numbers.

How can I count the numbers?

Upvotes: 2

Views: 829

Answers (2)

user2305193
user2305193

Reputation: 2059

correct me if I'm wrong but it sounds like you want the number of occurrences of the numbers in your vector, here's an alternative if that is the case:

arr=[1 2 2;3 3 3;5 0 0;0 0 0]; % example array where 1,2,3 occur 1x,2x,3x and 5=>1x, 0=>5x
[x(:,2),x(:,1)]=hist(arr(:),unique(arr(:)));

outputs sorted category as first column, occurrences as 2nd column:

x =

     0     5
     1     1
     2     2
     3     3
     5     1

Upvotes: 1

Wolfie
Wolfie

Reputation: 30047

You can just use nnz to get the number of non-zero elements in a logical array, so the number of elements in arr with the value 0 is

count = nnz( arr == 0 );

Please read Why is 24.0000 not equal to 24.0000 in MATLAB? for information about comparisons of floating point numbers, you may need to do

tol = 1e-6; % some tolerance on your comparison
count = nnz( abs(arr) < tol ); % abs(arr - x) for values equal to x within +/-tol

Upvotes: 2

Related Questions