%y(t+2) + 6y(t+1) + 9y(t) = 4, t>=0 %y(0) = 1.25, y(1) = -6 t=[1:30]; y(1) = 1.25; y(2) = -6; for m=3:30; y(m)=-6*y(m-1)-9*y(m-2)+4; end stem(t,y,'o') stem(t,y) pause; plot(t,y,'*') pause plot(t,y) pause; f = @(new_y) interp1(t,y, new_y, 'spline'); x=[1:.1:30]; for i = 1:291 ff(i)=f(x(i)); end for i = 1:291 yte(i)=0.25+(-3)^(x(i)-1)+(x(i)-1)*(-3)^(x(i)-1); end plot(x,ff,'r-',x,yte, 'b:') xlabel ('tempo') ylabel ('y') title ('Curvas contínuas: spline (vermelha) e teórica (azul tracejado)')