function Xn=Noise(X,noise,snr)

% AUTHOR : SHAHIS HASHIM (Research Scholar, IIT Madras)

% INPUT
    % X : Signal (arrey 1xn)
    % noise : type of noise ('pink', 'blue', 'red', 'violet', 'white')
    % snr ; required SNR level in dB
% OUTPUT
    % Xn : signal added with noise
    
% Part of this code contains codes written by Dr. Eng. Hristo Zhivomirov
%  Hristo Zhivomirov (2022). Pink, Red, Blue and Violet Noise Generation with Matlab
%  (https://www.mathworks.com/matlabcentral/fileexchange/42919-pink-red-blue-and-violet-noise-generation-with-matlab),
%  MATLAB Central File Exchange. 

switch noise
    case 'pink'
        N_ = pinknoise(length(X));
    case 'blue'
        N_ = bluenoise(length(X));
    case 'red'
        N_ = rednoise(length(X));
    case 'violet'
        N_ = violetnoise(length(X));
    case 'white'
        N_ = whitenoise(length(X));
end
A=db2mag(snr);
rt=rssq(X)/(rssq(N_)*A);
N=N_.*rt;

Xn=X+N';
end
function x = pinknoise(N)
validateattributes(N, {'double'}, ...
    {'scalar', 'integer', 'nonnan', 'finite'}, ...
    '', 'N', 1)
alpha = -1;
alpha = alpha/2;
x = randn(1, N);
NumUniquePts = ceil((N+1)/2);
X = fft(x);
X = X(1:NumUniquePts);
n = 1:NumUniquePts;
X = X.*(n.^alpha);
if rem(N, 2)
    X = [X conj(X(end:-1:2))];
    x = real(ifft(X));
else
    X = [X conj(X(end-1:-1:2))];
    x = real(ifft(X));
end
x = x - mean(x);
x = x/std(x, 1);
x = x(:);
end

function x = bluenoise(N)
validateattributes(N, {'double'}, ...
    {'scalar', 'integer', 'nonnan', 'finite'}, ...
    '', 'N', 1)
alpha = 1;
alpha = alpha/2;
x = randn(1, N);
NumUniquePts = ceil((N+1)/2);
X = fft(x);
X = X(1:NumUniquePts);
n = 1:NumUniquePts;
X = X.*(n.^alpha);
if rem(N, 2)
    X = [X conj(X(end:-1:2))];
    x = real(ifft(X));
else
    X = [X conj(X(end-1:-1:2))];
    x = real(ifft(X));
end
x = x - mean(x);
x = x/std(x, 1);
x = x(:);
end

function x = rednoise(N)
validateattributes(N, {'double'}, ...
    {'scalar', 'integer', 'nonnan', 'finite'}, ...
    '', 'N', 1)
alpha = -2;
alpha = alpha/2;
x = randn(1, N);
NumUniquePts = ceil((N+1)/2);
X = fft(x);
X = X(1:NumUniquePts);
n = 1:NumUniquePts;
X = X.*(n.^alpha);
if rem(N, 2)
    X = [X conj(X(end:-1:2))];
    x = real(ifft(X));
else
    X = [X conj(X(end-1:-1:2))];
    x = real(ifft(X));
end
x = x - mean(x);
x = x/std(x, 1);
x = x(:);
end

function x = violetnoise(N)
validateattributes(N, {'double'}, ...
    {'scalar', 'integer', 'nonnan', 'finite'}, ...
    '', 'N', 1)
alpha = 2;
alpha = alpha/2;
x = randn(1, N);
NumUniquePts = ceil((N+1)/2);
X = fft(x);
X = X(1:NumUniquePts);
n = 1:NumUniquePts;
X = X.*(n.^alpha);
if rem(N, 2)
    X = [X conj(X(end:-1:2))];
    x = real(ifft(X));
else
    X = [X conj(X(end-1:-1:2))];
    x = real(ifft(X));
end
x = x - mean(x);
x = x/std(x, 1);
x = x(:);
end

function x = whitenoise(N)
x=wgn(N,1,1);
end