Pythagorean triples - wrong output in loop

Hello, I have this piece of code, it computes pythagorean triples, then adds them in a matrix, but in output for some reason it adds lines with zeros. How do I change the code to run properly?

And 1 more thing how to make it print sorted by a+b+c column, not by a like now?

UPD. I have solved 1 part of the question with "R = reshape(nonzeros(R), I, 4);

"

function [R, I] = pyth_tri(N)
I = 0;
for a = 3:N/3
    for b = a:N/3
        for c = b:N
            if (a^2 + b^2) == c^2 && a ~= 0 && b ~= 0 && c ~= 0
                R(a, :) = [a+b+c, a, b, c]
                I = I + 1;
            end
        end
    end
end
end

Answer 1

[the cyclist]

You need

R(I+1, :) = [a+b+c, a, b, c];

rather than

R(a, :) = [a+b+c, a, b, c];

For sorting, after your run your algorithm, run

R = sortrows(R,1)