Help me about a code

If this code that I did it of fast Fourier transform that matlab use in y=fft(x),

 X = xlsread('Arrastre.xls',1,'B1:B1441');%presiom
[N,M] = size(X);
y = zeros (N,1);
n = 0 : N-1;
for k = 0 : N-1
    y(k+1) = sum(exp(-j*2*pi*n*k/N)*X);
end
y;

How is the code for DCT or Discrete Fourier transform that matlab use for y=dct(x)?

[John D'Errico]

Note this is absolutely not the code that MATLAB uses for fft.

Answer 1

[Walter Roberson]

https://www.mathworks.com/matlabcentral/fileexchange/49825-dct-y-

[bayran arrieta]

Do you know what is the equation exactly used in it? thank you beforehand

[Walter Roberson]

If you have the Signal Processing Toolbox then you can

dbtype dct