Sum of the element occurence

Greetings Matlab Community,

I've manage to sum up the occurrence of number 2 of the entire matrix by using this,

chromo = [1 1 2 4 6 1 ; 2 1 3 5 7 2];
sum(chromo(:) == 2)

How do i sum up the occurrence of number 2 in just a row in the matrix and not the entire matrix?

Answer 1

[Ameer Hamza]

If A is the matrix, you can do this as follow

numOfTwos = sum(A==2, 2);
myResult = numOfTwos(rowNumber);

The above will numOfTwos will give number fo two in all the rows of matrix A. If you just want it for one row, use

numOfTwos = sum(A(rowNumber, :) ==2, 2);

[yiwen yim]

Thank you for you reply. However, every time i try to run with rowNumber in the code it will gives this error,

'Undefined function or variable 'rowNumber'.'

Please explain further.

[Ameer Hamza]

You need to define rowNumber before running the code. For example in the beginning run

rowNumber = 3;

[Walter Roberson]

In your question you asked "How do i sum up the occurrence of number 2 in just a row in the matrix". Did you mean how to do it for one particular row? Or is the question about how to do it for each row ?

[Ameer Hamza]

@yiwen yim answer moved here

"I would like to know how to do it for each row."

[Ameer Hamza]

this line will tell the number of 2's in each row of A

numOfTwos = sum(A==2, 2);

[Ameer Hamza]

@yiwen yim answer moved here

"Also for a particular row."

[Ameer Hamza]

For particular row you can do this

numOfTwos = sum(A(3, :) ==2, 2);

It will tell you number of twos in row 3.

Answer 2

[yiwen yim]

I would like to know how to do it for each row.

[Ameer Hamza]

Please delete this answer, and discuss it in the comment section.

Answer 3

[yiwen yim]

Also for a particular row.