Even & Odd Discrete time Signals

I am writing a program to seperate, plot even and odd parts of a discrete time signal. Following is my code:

I am getting error at line 3 & 4. "Array indices must be positive integers or logical values."

Since I am trying to flip and invert the signal x[n] , so 'x(-n)' is obvious to use but I am getting error. Kindly help.

n= -3:4;
x=[0 0 0 2 3 -1 2 -3];
xe= ( x(n)+x(-n) )/2;
xo= ( x(n)-x(-n)  )/2;
subplot(311);stem(n,x);grid on; xlabel('n');ylabel('Amplitude');title('Original Signal');
subplot(312);stem(n,xe);grid on; xlabel('n');ylabel('Amplitude');title('Even Signal');
subplot(313);stem(n,xo);grid on; xlabel('n');ylabel('Amplitude');title('Odd Signal');

[ANAND AMAR]

Error in (line 3)

xe= ( x(n)+x(-n) )/2;

Answer 1

[S. Sukkrishvar Vijay]

n + (-1)^n

Answer 2

[Hafiz]

n= -3:4;
x=[0 0 0 2 3 -1 2 -3];
xe= ( x(n)+x(-n) )/2;

Array indices must be positive integers or logical values.

xo= ( x(n)-x(-n)  )/2;
subplot(311);stem(n,x);grid on; xlabel('n');ylabel('Amplitude');title('Original Signal');
subplot(312);stem(n,xe);grid on; xlabel('n');ylabel('Amplitude');title('Even Signal');
subplot(313);stem(n,xo);grid on; xlabel('n');ylabel('Amplitude');title('Odd Signal');

Answer 3

[Paul]

Matlab doesn't support zero or negtaive indices, so it won't be possible to implement this operation using ordinary vector indexing.

One approach is to define a fucntion that returns elements of the signal x[n] for values of n. One option is to use an anonymous function.

Though not stated expliclty, it appears that x[n] = 0 for n < 0 and x[n] = 0 for n > 4.

x = @(n) (n == 0)*2 + (n == 1)*3 + (n == 2)*-1 + (n == 3)*2 + (n == 4)*-3;
n  = -5:5;
tiledlayout(3,1);
nexttile,stem(n,x(n)),title('x[n]')

xe = (x(n) + x(-n))/2;
nexttile,stem(n,xe);title('xe[n]')

xo = (x(n) - x(-n))/2;
nexttile,stem(n,xo);title('xo[n]')

all(x(n) == xe + xo)

ans = logical
   1

Answer 4

[Tannu]

clc;
clear all;
close all;
n = [-5,-4,-3,-2,-1,0,1,2,3,4,5];
x1 = [1,2,3,4,5,6,5,4,3,2,1];
x2 = [-5,-4,-3,-2,-1,0,1,2,3,4,5];
x3 = [3,1,4,2,6,5,7,0,2,1,4];
signals = {x1, x2, x3};
N = length(n);
mid = (N+1)/2;
for k = 1:3
    x = signals{k};
    
    Even_flag = 1;
    Odd_flag = 1;
    
    % Check Even and Odd separately
    for i = 1:N
        if x(i) ~= x(N-i+1)
            Even_flag = 0;
            break;
        end
    end
    
    for i = 1:N
        if x(i) ~= -x(N-i+1)
            Odd_flag = 0;
            break;
        end
    end
    
    % For odd signal, middle value must be 0
    if Odd_flag == 1
        if x(mid) ~= 0
            Odd_flag = 0;
        end
    end
    
    % Display result
    if Even_flag == 1
        fprintf('Signal %d is Even\n', k);
    elseif Odd_flag == 1
        fprintf('Signal %d is Odd\n', k);
    else
        fprintf('Signal %d is Neither Even nor Odd\n', k);
    end
end

Signal 1 is Even

Signal 2 is Odd

Signal 3 is Neither Even nor Odd

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