How to Use stem() Function in MATLAB to Plot Discrete-Time Signals

h = stem(Y)               
% Plots Y values against their index numbers h = stem(X, Y)            
% Plots Y values at custom X coordinates h = stem(..., 'filled')   % Fills the top markers h = stem(ax, ...)         % Targets a specific axes object h = stem(..., Name, Value)% Customizes colors, line widths, and marker types

% Define a sequence x[n] from n = 0 to 10 n = 0:10;
x = [0 1 2 3 2 1 0 -1 -2 -1 0];
stem(n, x, 'filled', 'MarkerFaceColor', 'r', 'LineWidth', 1.5);
title('Basic Discrete Sequence x[n]');
xlabel('Sample index n');
ylabel('Amplitude');
grid on;

n = -5:10;
delta = (n == 0);
% Kronecker delta δ[n] step  = (n >= 0);
% Unit step u[n]  sub
plot(2,1,1);
stem(n, delta, 'filled', 'MarkerSize', 8);
title('Unit Impulse δ[n]');
grid on;
sub
plot(2,1,2);
stem(n, step, 'filled', 'Color', 'm');
title('Unit Step u[n]');
grid on;

[X, Y] = meshgrid(-5:1:5, -5:1:5);
Z = X .* exp(-X.^2 - Y.^2);
% 3D Gaussian surface points  stem3(X, Y, Z, 'filled', 'MarkerSize', 6);
title('3D Discrete Surface using stem3()');
xlabel('X');
ylabel('Y');
zlabel('Z');
colorbar;

b = [1 0.5];
a = [1 -0.9];
% IIR filter coefficients [h, n] = impz(b, a, 30);
% Calculate impulse response  stem(n, h, 'filled', 'MarkerFaceColor', 'g');
title('Impulse Response of H(z) = (1 + 0.5z^{-1}) / (1 - 0.9z^{-1})');
xlabel('n');
ylabel('h[n]');
grid on;