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Plotting Discrete Time Functions

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Bradley Johnson
Bradley Johnson 2020-9-22
回答： Satyam 2024-8-5
I need to plot 5 cos(π n /6 - π/2) as a discrete tim signal. But I am not getting the proper result.
n = [-5:0.001:5];
y = 5*cos(pi*(n/2)-(pi/2));
stem(n,y);
What am I missing from this code to get the discrete time signals?

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回答（3 个）

Austin Holmes
Austin Holmes 2021-11-11
The original poster asked for the discrete time signal not the continuous time signal. A discrete time signal just means sampling your continuous signal at discrete time intervals.
The simplest way this can be done is by increasing your step in n.
n = [-5:0.25:5];
y = 5*cos(pi*(n/2)-(pi/2));
stem(n,y);
The proper way to do this would be determining a sampling rate and implementing it in your code.
Freedom TSOKPO
Freedom TSOKPO 2020-9-23
I've just began with Matlab and I don't even know the function stem.
But I think this code can do it
clear all; clc;
n = -5:0.001:5;
y = 5*cos((n-1)*pi/2); %5*cos(pi*(n/2)-(pi/2));
figure
% axis([-6 6 -4 4]);
plot(n,y);
Satyam
Satyam 2024-8-5
t = -1:0.01:1;
impulse_continuous = @(t) t == 0;
unit_step_continuous = @(t) t >= 0;
unit_ramp_continuous = @(t) t .* (t >= 0);
exponential_continuous = @(t) exp(t);
sine_continuous = @(t) sin(2*pi*t);
cosine_continuous = @(t) cos(2*pi*t);
n = -10:10;
impulse_discrete = @(n) n == 0;
unit_step_discrete = @(n) n >= 0;
unit_ramp_discrete = @(n) n .* (n >= 0);
exponential_discrete = @(n) exp(n/10);
sine_discrete = @(n) sin(2*pi*n/10);
% Discrete Cosine Function
cosine_discrete = @(n) cos(2*pi*n/10);
% Plot Continuous Functions
figure;
subplot(3,2,1);
plot(t, impulse_continuous(t), 'LineWidth', 2);
title('Continuous Impulse Function');
xlabel('Time (t)');
ylabel('\delta(t)');
axis([-1 1 -0.5 1.5]);
grid on;
subplot(3,2,2);
plot(t, unit_step_continuous(t), 'LineWidth', 2);
title('Continuous Unit Step Function');
xlabel('Time (t)');
ylabel('u(t)');
axis([-1 1 -0.5 1.5]);
grid on;
subplot(3,2,3);
plot(t, unit_ramp_continuous(t), 'LineWidth', 2);
title('Continuous Unit Ramp Function');
xlabel('Time (t)');
ylabel('r(t)');
axis([-1 1 -0.5 1.5]);
grid on;
subplot(3,2,4);
plot(t, exponential_continuous(t), 'LineWidth', 2);
title('Continuous Exponential Function');
xlabel('Time (t)');
ylabel('e^t');
axis([-1 1 -0.5 3]);
grid on;
subplot(3,2,5);
plot(t, sine_continuous(t), 'LineWidth', 2);
title('Continuous Sine Function');
xlabel('Time (t)');
ylabel('sin(2\pi t)');
axis([-1 1 -1.5 1.5]);
grid on;
subplot(3,2,6);
plot(t, cosine_continuous(t), 'LineWidth', 2);
title('Continuous Cosine Function');
xlabel('Time (t)');
ylabel('cos(2\pi t)');
axis([-1 1 -1.5 1.5]);
grid on;
% Plot Discrete Functions
figure;
subplot(3,2,1);
stem(n, impulse_discrete(n), 'filled');
title('Discrete Impulse Function');
xlabel('n');
ylabel('\delta[n]');
axis([-10 10 -0.5 1.5]);
grid on;
subplot(3,2,2);
stem(n, unit_step_discrete(n), 'filled');
title('Discrete Unit Step Function');
xlabel('n');
ylabel('u[n]');
axis([-10 10 -0.5 1.5]);
grid on;
subplot(3,2,3);
stem(n, unit_ramp_discrete(n), 'filled');
title('Discrete Unit Ramp Function');
xlabel('n');
ylabel('r[n]');
axis([-10 10 -5 15]);
grid on;
subplot(3,2,4);
stem(n, exponential_discrete(n), 'filled');
title('Discrete Exponential Function');
xlabel('n');
ylabel('e^{n/10}');
axis([-10 10 -0.5 3]);
grid on;
subplot(3,2,5);
stem(n, sine_discrete(n), 'filled');
title('Discrete Sine Function');
xlabel('n');
ylabel('sin(2\pi n/10)');
axis([-10 10 -1.5 1.5]);
grid on;
subplot(3,2,6);
stem(n, cosine_discrete(n), 'filled');
title('Discrete Cosine Function');
xlabel('n');
ylabel('cos(2\pi n/10)');
axis([-10 10 -1.5 1.5]);
grid on;

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