Why do I get "Array indices must be positive integers or logical values" error

t=0:0.01:4;

h1=t.*cos(2.*pi.*t);

subplot(6,1,1);

plot(t,h1);

title 'p(t)';

grid on;

h2=t.*exp(-2.*t);

subplot(6,1,2);

plot(t,h2);

title 'q(t)';

grid on;

h12=h1+h2;

subplot(6,1,3);

plot(t,h12);

title 's(t)';

grid on;

h3=u(t)-u(t-5);

th=0:0.01:8;

h=conv(h12,h3)*0.01;

subplot(6,1,4);

plot(th,h)

grid on;

legend('h(t)')

title 'overall impulse response'

tx=0:0.01:2;

x=tx.*exp(-2.*tx);

subplot(6,1,5);

plot(tx,x)

grid on;

legend('x(t)')

title 'Input signal'

ty=0:0.01:10;

y=conv(x,h)*0.01;

subplot(6,1,6);

plot(ty,y)

grid on;

legend('y(t)')

title 'System Response'

syms t;

int(y,t,-inf,inf);

Answer 1

[Dyuman Joshi]

Because you are defining an array using negetive indexes.

> h3=u(t)-u(t-5); %u is undefined in your code

As you have defined t=0:0.01:4, values of t-5 become negetive numbers, which can not be used as indexes to define an array.

[Muhammad Saad]

Thanks