MATLAB: I am reading a .wav file and I have been able to plot it. I am now trying to perform a FFT on two of the three channels; I am trying but I keep getting ‘Undefined function ‘fft’ for input arguments of type ‘int16’ ‘.

errorfftint16MATLABundefinedwavwavread

Firstly what code would you use to perform the fft? Secondly how do I get rid of this Error?

Convert int16 data to double using double()

fft needs data to be in double.

data = double(data) ;

I think that is covered in just about any textbook. The DFT is computationally intensive to implement as a matrix-vector multiplication.

The NxN DFT matrix times a Nx1 signal vector involves N^2 multiplications and N additions.

By exploiting certain symmetries the fft() reduces that significantly.

If you just read the wikipedia page, you'll find references:

Then you just do

 t = 0:0.001:1-0.001;
 I = cos(2*pi*100*t);
 Q = sin(2*pi*100*t);
 sig1 = I+1j*Q;
 dftsig1 = fft(sig1);

Do the same for I2 and Q2, etc.