How to get numbers from rows in a matrix, to separate vectors?

I have a matrix of grades, I want to put the number of times grades repeat in each row into separate vectors so I can plot it in a scatter plot.

I have the matrix

grades=

7 7 4

12 10 10

-3 7 2

10 12 12

4 2 10

10 7 4

7 7 9

12 12 12

2 7 12

0 -3 2

4 10 2

2 12 10

10 3 4

12 12 12

I want to know how many times each number repeats in each row, and put them in a vector for each row

Answer 1

[Samatha Aleti]

According to my understanding you are trying to get the count of numbers in each row and save it in another vector. You can use “find” function to do this.

Let “grades” be the matrix, “out” be the output vector which holds the count of element “1” in each row.Here is a sample code to do this:

grades = [1 2 3; 3 2 1; 1 2 1; 1 2 3; 1 3 1;1 1 3];  % Let 
numRows = size(grades,1); % Number of rows 
out= zeros(1,numRows); % Initialize a vector to store the count 
for i = 1:numRows 
    out(i) = length(find(grades(i,:) == 1));   
end 

Refer the following document link for detailed explanation on using "find":

https://www.mathworks.com/help/matlab/ref/find.html

[Stephen23]

More efficient than using length(find(...)):

nnz(grades(i,:) == 1)