Is my matlab code for the sinc signal below correct.

I want to create and plot the signal equation below in matlab. The Coefficients ak are uniformly distributed in [−1, 1]. c is a constant.

Here is my code:

%************ Variable declaration******************

t = -20:0.1:20;

p = -10:1:10

data = 0;

signal = zeros(1,length(t)); %for spped allocations

c = 25 % constant

ak = -1 + 2*rand(1,21); % numbers in the interval (a,b) with the formula r = a + (b-a).*rand(N,1).

count = 1;

%********************************************************************************************

for i = t

for k = p

data = data + c*ak(k+11)*sinc(i-k);

end

signal(counter) = data;

counter = counter + 1;

end

plot(t,signal);

Thanks in advance.

Answer 1

[Torsten]

%************ Variable declaration******************
rng('default')
t = -20:0.1:20;
signal = zeros(1,length(t)); %for spped allocations
c = 25;  % constant
ak = -1 + 2*rand(1,21); % numbers in the interval (a,b) with the formula r = a + (b-a).*rand(N,1).
%********************************************************************************************
for i = 1:length(t)
    T = t(i);
    data = 0;
    for k = -10:1:10
        data = data + ak(k+11)*sinc(T-k); 
    end
    signal(i) = c*data;
end
plot(t,signal)

Answer 2

[Chunru]

%************ Variable declaration******************
t = -20:0.1:20;
p = -10:1:10;
signal = zeros(1,length(t)); %for spped allocations
c = 25;  % constant
ak = -1 + 2*rand(1,21); % numbers in the interval (a,b) with the formula r = a + (b-a).*rand(N,1).
%********************************************************************************************
for i = 1:length(t)
    data = 0;

    for k = 1:length(p)
        data = data + c*ak(k)*sinc(t(i)-p(k)); 
    end
    signal(i) = data;
end
plot(t,signal);

[Afuaab Koohg]

Thanks Chunru.

I see your modifications and thanks for that.

Could you confirm that the implementation is right for the equation above.

My code was giving me different graphs each time I run the code and made me think it was wrong the way I implemented.

[Chunru]

ak = -1 + 2*rand(1,21);

The above line generate different random numbers for each run so that you will see different results. If you want to have same results:

rng('default');     % this will reset the seed number for random number generator
ak = -1 + 2*rand(1,21);

[Afuaab Koohg]

Thanks @Chunru

[Torsten]

In the code above, "data" has to be reset to 0 after the k-loop.

Further

data = data + c*ak(k)*sinc(t(i)-p(k));

instead of

data = data + c*ak(k)*sinc(i-p(k));

Otherwise the code is wrong.

[Chunru]

@Torsten Yes. You are right. Corrected.

[Afuaab Koohg]

Thanks so much @Torsten and @Chunru: I accept the solutions that you have provided.

Are you able to help my other question please?