Matlab - Ecuación recorra un vector

u=linspace(0,65);

P = E*A/l0*((h/l0).^2*u-3/2*h*u.^2/l0^2+1/2*u.^3/l0.^2)+k*u;

plot(u,P,'g')

title('Respuesta P-u')

clear all

E=5*rand; A=20*rand;  l0=100*rand;

h=300*rand;

k= [0,0.4,0.8,1.6,2.15];

u=linspace(0,65);

close all

hold on

for i=1:length(k);

P(i,:) = E*A/l0*((h/l0).^2*u-3/2*h*u.^2/l0^2+1/2*u.^3/l0.^2)+k(i)*u;

plot(u,P(i,:),'color', rand(1,3))

  a{i}=['k=',num2str(i)];

  legend(a)

  grid on

pause(1)

end

hold off

title('Respuesta P-u')