# Plot time continous singal by using a sum of time invariant signals

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Jenny Sundström on 20 May 2022
Answered: Chandra on 23 May 2022
I want to make a plot of the following: Where the input x(t) is given as: and x[n] is the sampled signal of x(t). Below is the code of how I tried to solve it:
f_s = 2,1; Ts = 1/f_s;
t = -5:Ts:5; x = @(t)((3/2) + (3/10) sin(2pit) + sin(2pit/3) - sin(2pit/10)).sinc(t);
syms n
x_t = @(t) symsum(x(n/f_s)sinc((t-nTs)/Ts), n, -5, 5);
x_0 = x_t(t);
plot(x_0, t)
But I can't seem to make it work nor do I understand why. Below are error messages:
Error using symengin Division by zero.
Error in sym/symsum (line 70) rSym = mupadmex('symobj::map',fsym.s,'symobj::symsum',x.s,a.s,b.s);
Error in matlabasklol>@(t)symsum(x(n/f_s)sinc((t-nTs)/Ts),n,-5,5) (line 7) x_t = @(t) symsum(x(n/f_s)sinc((t-nTs)/Ts), n, -5, 5);
Error in matlabasklol (line 8) x_0 = x_t(t);
Would be very grateful for some help or pointers here, many thanks.

Chandra on 23 May 2022
Hi,
Replace the “symsum” function with “for” loop and plot the signal
f_s = 2;
Ts = 1/f_s;
t = -5:Ts:5; % change the the interval of signal like -10:Ts/5:10
x = @(t)((3/2) + (3/10)*sin(2*pi*t) + sin(2*(pi)*t/3) - sin(2*pi*t/10)).*sinc(t);
x_0 = zeros(1,length(t));
for j = 1:length(t)
for i = -6:6
a = x(i)*sinc((j-i*Ts)/Ts);
x_0(j) = a + x_0(j);
end
end
plot(t,x_0)
Refer the below link for further reference about using the sin in degrees and radians