Complex Cepstral Transform on Audio in MATLAB Hello I am trying to computer the Complex Cepstral Transform of an audio signal. I am using wavread to get an array of data type double precision. However, when I try to use cceps to do the Complex Cepstral Transform, I get the following error: 

Error using cceps&gt;chkinput (line 157)
The input signal X must be real.

Error in cceps (line 73)
chkinput(x);


Is there something I am doing wrong or is there another way to do this transform? Thank you! 

Also, I tried computing this manually using the definition of the complex cepstral transform as follows:

C=ifft(ln(fft(f)))


where f is the array of double precision audio data. However, this returns the error: 
Undefined function 'ln' for input arguments of type 'double'.
Natural log in matlab is 'log(x)' and log to the base 10 is 'log10(x)'

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