DSP - Auto Correlation (Scilab Code with Plot)

Scilab Code:

//Auto Correlation of x(n) is given as:

//R(k) = summation of x(n)*x(n-k) for n = -INF to INF

//Position of origin in the given sequence doesn't matter,

//Its only taken to plot the given sequence.

clc; close; clear;

x = input("Enter the sequence: ");

x_origin = input("Enter the position of origin in the sequence: ");

//plot the given sequence

subplot(2,1, 1);

x_lower = -(x_origin - 1);

x_upper = length(x) - x_origin;

n = x_lower : x_upper;

plot2d3(n, x, style=color("red"));

xtitle("x(n)","n");

a = gca();

a.children.children(1).thickness = 2;

a.y_location = "origin";

//plot the auto correlation

subplot(2,1, 2);

L = length(x);

n = -L+1:L-1;   //Elsewhere it'll be 0

y = xcorr(x);

disp(y, "Auto Correlation = ");

plot2d3(n, y, style=color("blue"));

xtitle("Auto Correlation of x(n)","n");

//The above code can also be done as follows:

//[y, ind] = xcorr(h);

//plot2d3(ind, y);

//No need to define the range.

a = gca();

a.y_location = "origin";

a.children.children(1).thickness = 2;

Console I/O:

Plot: