Dear Jun,

Your calculation makes sense but note that with 3 cycles at 2 Hz all your pre-stimulus points will be computed based on both pre- and post-stimulus data. The first point at -50ms will have slightly more than half of its support before the stimulus and the later points even less than that. 

The frequency axis does not depend of the number of cycles but you can change it manually by specifying your desired frequency bins. You can have more frequency bins than your true frequency resolution and in this case the adjacent bands will not be linearly independent.

Best,

Vladimir

On Sun, Nov 4, 2012 at 4:41 PM, Jun Wang <[log in to unmask]> wrote:

Dear Vladimir,

  I am doing TF right now. My data has 800ms prestimulus window. Based on the spm manual, in order to get low frequency (2Hz), I set wavelets cycles number to be 3. then  (3/2)* 1000/2 =750ms which is within my 800ms pre stimulus window range. Is this the correct way to set. Also I noticed if I set frequencies of interest to be [2:48], the output TF frequecies will be always[2 3 4.....48] no matter how many wavelet cycles I set. Shouldn't the frequency resolution depend on wavelet cycles setting?  Could you help me out here.

thanks

Jun