Do I use the "for loop" correct or efficiently?

Is there a better way or more efficient?

n = 3500;
t_s = 0;
t_f = 3500;
t = linspace(t_s,t_f,n);

a = zeros(1,n);

for i = 1:1800
    a(i) = 50/3.6;
    for n = 1800:3000
        a(i) = 90/3.6;
        for n = 3000:3500
            a(i) = 0;
        end
    end
end

Answer 1

[per isakson]

Replace the loops by

a(1:1800)=50;
a(1801:3000)=90;
a(3001:3500)=0;

to match the figure