Adding to an array within a For loop?

%%I am trying to add a student's number to the gpa4 and class_honors lists if they meet my if statement conditionals but my output still shows them as empty arrays

rng('default')
data(:,1) = randperm(300); %student number
data(:,2) = randi(4,300,1) + 14; %class year
data(:,3) = randi(20,300,1)/10 + 2; %gpa
checkvalues = mean(data);

gpa4 = [];
class_honors = [];
class_psych = 0;
ctr = 1; 

for i = 1:300
    if data(i,3) == 4.0
        gpa4 = gpa4 + data(i,1);
    end 
    if (data(i,2) == 2015) & (data(i,3) >= 3.5)
        class_honors = class_honors + data(i,1);
    end
    if (data(i,2) == 2018) & (data(i,3) >= 3.0)
        class_psych + 1;
    end
end
disp('Students with a 4.0:')
disp(gpa4)
disp('Seniors with honors:')
disp(class_honors)
disp('# of first year potential psychology majors:')
disp(class_psych)

student_one = data(1,3);
disp('Student One GPA:')
disp(student_one)

class_17 = std(data(:,2));
disp('Class of 17 GPA Standard Deviation:')
disp(class_17)

[Caroline Culver]

my output currently looks like this:

Students with a 4.0:

Seniors with honors:

# of first year potential psychology majors:

0

Student One GPA:

3.8000

Class of 17 GPA Standard Deviation:

1.0638

Answer 1

[David Hill]

No loop needed.

gpa4=nnz(data(:,3) == 4);
class_honors=nnz(data(:,2) == 2015 & data(:,3) >= 3.5);
class_psych=nnz(data(:,2) == 2018 & data(:,3) >= 3.0);