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Duvida Matlab

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Considere o sinal de tempo discreto x[n] = 2sin[0.02π n](u[n + 50]− u[n − 50]) .

Determine e apresente a resposta dos seguintes sistemas ao sinal de entrada x[n], para −60 ≤ n ≤ 60 :

1y [n] = 0.1x[n −1]− 0.7x[n − 2]+ 0.2x[n − 4];

estou a tentar resolver este problema utilizando o matlab.

O codigo criado por mim foi o seguinte:

function ex4_1a( xs )

syms ns;





for k=1:length(n),

if n(k)<-50, y(k)=0; x(k)=0;

elseif n(k)>=50, y(k)=0; x(k)=0;

else y(k)=subs(y2,ns,k);x(k)=subs(xs, ns, k);




hold all;


legend(' x[n]=2sin[0.02*pi*n](u[n+50]-u(n-50))',' y[n]=0.1x[n-1]-0.7x[n-2]+0.2x[n-4]',2,'Location','NorthEast');

title('Resposta do sistema no intervalo [-60,60]');

Mas depois a tentar correr o programa introduzindo 2sin[0.02π n](u[n + 50]− u[n − 50]) como sendo uma string da o seguinte erro:


x =


>> ex4_1a(x)

??? Conversion to double from sym is not possible.

Error in ==> ex4_1a at 13

else y(k)=subs(y2,ns,k);x(k)=subs(xs, ns, k);

Alguem me pode dizer de que maneira devo introduzir a funcao de entrada?

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