Time Scaling In Discrete Time Signals

Hello everyone. I want to apply time scaling property to my signal. It is hard for me to apply for the signals especially like x[4n], x[2n], x[1/3n]. I know there must be mod calculation because the values should be integer but i could not write the code can someone help me please?

n=[-2 -1 0 1 2 3 4];

x=[3 1 0 4 6 2 9];

Answer 1

[Setsuna Yuuki.]

n=[-2 -1 0 1 2 3 4];
x=[3 1 0 4 6 2 9];
stem(n,x);hold on; %original
n2 = 4*n;
stem(n2,x); %x4
n3 = 2*n;
stem(n3,x);%x2

to x[1/3n] I don't know :(

[enrique128]

I don't know too and the point is that. I just guess that we'll use mod :)

[Foysal Ahmmed]

okey. but the figure should include 0 amplitude for the rest of the integer sample value. Again we cant find x[n/2] this way. because they includes fraction sample n=1.5 .

[Luke Ramel]

this is wrong, since if we have a multiplier of 2 to the time (n) the x-axis values should be divided by 2 since we are scaling time.

Answer 2

[tuan]

x = [3 1 0 4 6 2 9];

n=-2:4

% Time scaling factors

factors = 2; % efficiency

for factor = factors

% Determine scaling type (compression or expansion)

if factor > 1

scaling_type = 'Compression';

else

scaling_type = 'Expansion';

end

% Time-scaled indices based on scaling type

if factor > 1

% Compression: select indices where n is a multiple of factor

indices = find(mod(n, factor) == 0);

n_scaled = n(indices);

x_scaled = x(indices);

else

% Expansion: replicate and interpolate for integer multiples of factor/n

n_scaled = n / factor;

x_scaled = zeros(size(n));

for i = 1:length(n_scaled)

% Find the closest integer in n for the current n_scaled(i)

[~, closest_idx] = min(abs(n - n_scaled(i)));

x_scaled(i) = x(closest_idx);

end

end

% Plot original and time-scaled signals

figure(1)

stem(n, x);

title('Original')

xlabel('n');

ylabel('Amplitude');

axis([-5,5,0,10])

figure(2)

stem(n_scaled, x_scaled);

xlabel('n');

ylabel('Amplitude');

title('Time Scaling of Discrete-Time Signal');

axis([-5,5,0,10])

end